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ds18b20: Add a C implementation and inprove documentation
This commit adds a C implementation for the DS18B20. The C++ implementation was untouched (ie: it does not wrap the C implementation). This can be done in the future if desired. In addition, add an ascii-schematic to both the .h and .hpp files to better illustrate how to wire up the DS 1-wire interface for the UART. Signed-off-by: Jon Trulson <jtrulson@ics.com>
This commit is contained in:
Jon Trulson
Noel Eck
parent
5088ee99e6
commit
6d437c8007
@ -116,6 +116,7 @@ add_example (tsl2561)
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add_example (collision)
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add_example (moisture)
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add_example (led)
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add_example (ds18b20)
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# Custom examples
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add_custom_example (nmea_gps_i2c-example-c nmea_gps_i2c.c nmea_gps)
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81
examples/c/ds18b20.c
Normal file
81
examples/c/ds18b20.c
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@ -0,0 +1,81 @@
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/*
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* Author: Jon Trulson <jtrulson@ics.com>
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* Copyright (c) 2016 Intel Corporation.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <unistd.h>
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#include <stdio.h>
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#include <signal.h>
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#include "ds18b20.h"
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bool shouldRun = true;
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void sig_handler(int signo)
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{
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if (signo == SIGINT)
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shouldRun = false;
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}
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int main(int argc, char **argv)
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{
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signal(SIGINT, sig_handler);
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//! [Interesting]
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printf("Initializing...\n");
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// Instantiate an DS18B20 instance using the uart 0
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ds18b20_context sensor = ds18b20_init(0);
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if (!sensor)
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{
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printf("ds18b20_init() failed.\n");
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return(1);
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}
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printf("Found %d device(s)\n\n", ds18b20_devices_found(sensor));
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// update and print available values every second
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while (shouldRun)
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{
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// update our values for all sensors
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ds18b20_update(sensor, -1);
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int i;
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for (i=0; i<ds18b20_devices_found(sensor); i++)
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{
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printf("Device %02d: Temperature: %f C\n",
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i, ds18b20_get_temperature(sensor, i));
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}
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printf("\n");
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sleep(2);
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}
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printf("Exiting...\n");
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ds18b20_close(sensor);
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//! [Interesting]
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return 0;
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}
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@ -1,5 +1,9 @@
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set (libname "ds18b20")
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set (libdescription "upm DS18B20 1-wire Temperature sensor")
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set (module_src ${libname}.cxx)
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set (module_hpp ${libname}.hpp)
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upm_module_init()
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upm_mixed_module_init (NAME ds18b20
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DESCRIPTION "DS18B20 1-wire Temperature sensor"
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C_HDR ds18b20.h
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C_SRC ds18b20.c
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CPP_HDR ds18b20.hpp
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CPP_SRC ds18b20.cxx
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# FTI_SRC ds18b20_fti.c
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# CPP_WRAPS_C
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REQUIRES upmc-utilities mraa)
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396
src/ds18b20/ds18b20.c
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396
src/ds18b20/ds18b20.c
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@ -0,0 +1,396 @@
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/*
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* Author: Jon Trulson <jtrulson@ics.com>
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* Copyright (c) 2016 Intel Corporation.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <assert.h>
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#include "ds18b20.h"
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// I'd rather use MRAA_UART_OW_ROMCODE_SIZE defined in uart_ow.h, but
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// this then can't be used to specify array sizes since it's a static
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// const int, rather than a define. This should be fixed in MRAA (PR
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// submitted 9/2016). Until then, work around it.
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#if !defined(MRAA_UART_OW_ROMCODE)
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# define ROMCODE_SIZE 8
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#else
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# define ROMCODE_SIZE MRAA_UART_OW_ROMCODE
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#endif
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// an internal struct we use to store information on the devices
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// found during initialization
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typedef struct _ds18b20_info_t {
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uint8_t id[ROMCODE_SIZE]; // 8-byte romcode id
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float temperature;
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DS18B20_RESOLUTIONS_T resolution;
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} ds18b20_info_t;
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// internal utility function forward to read temperature from a single
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// device
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static float readSingleTemp(const ds18b20_context dev, unsigned int index);
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ds18b20_context ds18b20_init(unsigned int uart)
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{
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ds18b20_context dev =
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(ds18b20_context)malloc(sizeof(struct _ds18b20_context));
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if (!dev)
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return NULL;
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// zero out context
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memset((void *)dev, 0, sizeof(struct _ds18b20_context));
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dev->ow = NULL;
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if (!(dev->ow = mraa_uart_ow_init(uart)))
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{
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printf("%s: mraa_uart_ow_init() failed.\n", __FUNCTION__);
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ds18b20_close(dev);
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return NULL;
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}
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// iterate through the bus and build up a list of detected DS18B20
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// devices (only)
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mraa_result_t rv;
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if ((rv = mraa_uart_ow_reset(dev->ow)) != MRAA_SUCCESS)
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{
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printf("%s: mraa_uart_ow_reset() failed, no devices detected\n",
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__FUNCTION__);
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ds18b20_close(dev);
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return NULL;
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}
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uint8_t id[ROMCODE_SIZE];
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rv = mraa_uart_ow_rom_search(dev->ow, 1, id);
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if (rv == MRAA_ERROR_UART_OW_NO_DEVICES)
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{
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// shouldn't happen, but....
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printf("%s: mraa_uart_ow_rom_search() failed, no devices detected\n",
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__FUNCTION__);
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ds18b20_close(dev);
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return NULL;
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}
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if (rv == MRAA_ERROR_UART_OW_DATA_ERROR)
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{
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printf("%s: mraa_uart_ow_rom_search() failed, Bus/Data error\n",
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__FUNCTION__);
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ds18b20_close(dev);
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return NULL;
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}
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while (rv == MRAA_SUCCESS)
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{
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// The first byte (id[0]]) is the device type (family) code. We
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// are only interested in the family code for these devices.
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if ((uint8_t)id[0] == DS18B20_FAMILY_CODE)
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{
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ds18b20_info_t *dsPtr =
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(ds18b20_info_t *)realloc((void *)dev->devices,
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sizeof(ds18b20_info_t) *
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(dev->numDevices + 1));
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if (!dsPtr)
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{
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printf("%s: realloc(%d) failed\n",
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__FUNCTION__,
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sizeof(ds18b20_info_t) * (dev->numDevices + 1));
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ds18b20_close(dev);
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return NULL;
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}
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dev->devices = dsPtr;
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// copy in the romcode
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memcpy(dev->devices[dev->numDevices].id, id,
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ROMCODE_SIZE);
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// set defaults for now
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dev->devices[dev->numDevices].temperature = 0.0;
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dev->devices[dev->numDevices].resolution =
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DS18B20_RESOLUTION_12BITS;
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dev->numDevices++;
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}
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// on to the next one
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rv = mraa_uart_ow_rom_search(dev->ow, 0, id);
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}
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if (!dev->numDevices)
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{
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printf("%s: no DS18B20 devices found on bus\n", __FUNCTION__);
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ds18b20_close(dev);
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return NULL;
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}
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// iterate through the found devices and query their resolutions
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int i;
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for (i=0; i<dev->numDevices; i++)
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{
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// read only the first 5 bytes of the scratchpad
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static const int numScratch = 5;
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uint8_t scratch[numScratch];
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_READ_SCRATCHPAD,
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dev->devices[i].id);
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int j;
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for (j=0; j<numScratch; j++)
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scratch[j] = (uint8_t)mraa_uart_ow_read_byte(dev->ow);
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// config byte, shift the resolution to bit 0
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scratch[4] >>= _DS18B20_CFG_RESOLUTION_SHIFT;
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switch (scratch[4] & _DS18B20_CFG_RESOLUTION_MASK)
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{
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case 0: dev->devices[i].resolution = DS18B20_RESOLUTION_9BITS; break;
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case 1: dev->devices[i].resolution = DS18B20_RESOLUTION_10BITS; break;
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case 2: dev->devices[i].resolution = DS18B20_RESOLUTION_11BITS; break;
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case 3: dev->devices[i].resolution = DS18B20_RESOLUTION_12BITS; break;
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}
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// reset the bus
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mraa_uart_ow_reset(dev->ow);
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}
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return dev;
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}
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void ds18b20_close(ds18b20_context dev)
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{
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assert(dev != NULL);
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if (dev->devices)
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free(dev->devices);
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if (dev->ow)
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mraa_uart_ow_stop(dev->ow);
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free(dev);
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}
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void ds18b20_update(const ds18b20_context dev, int index)
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{
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assert(dev != NULL);
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if (index >= dev->numDevices)
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{
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printf("%s: device index %d out of range\n", __FUNCTION__, index);
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return;
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}
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// should we update all of them?
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bool doAll = (index < 0) ? true : false;
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if (doAll)
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{
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// if we want to update all of them, we will first send the
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// convert command to all of them, then wait. This will be
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// faster, timey-wimey wise, then converting, sleeping, and
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// reading each individual sensor.
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int i;
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for (i=0; i<dev->numDevices; i++)
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_CONVERT, dev->devices[i].id);
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}
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else
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_CONVERT, dev->devices[index].id);
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// wait for conversion(s) to finish
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usleep(750000); // 750ms max
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if (doAll)
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{
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int i;
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for (i=0; i<dev->numDevices; i++)
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dev->devices[i].temperature = readSingleTemp(dev, i);
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}
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else
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dev->devices[index].temperature = readSingleTemp(dev, index);
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}
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// utility function to read temp data from a single sensor
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static float readSingleTemp(const ds18b20_context dev, unsigned int index)
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{
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assert(dev != NULL);
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if (index >= dev->numDevices)
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{
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printf("%s: device index %d out of range\n", __FUNCTION__, index);
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return 0.0;
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}
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static const int numScratch = 9;
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uint8_t scratch[numScratch];
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// read the 9-byte scratchpad
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_READ_SCRATCHPAD,
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dev->devices[index].id);
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int i;
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for (i=0; i<numScratch; i++)
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scratch[i] = (uint8_t)mraa_uart_ow_read_byte(dev->ow);
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// validate cksum -- if we get an error, we will warn and simply
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// return the current (previously read) temperature
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uint8_t crc = mraa_uart_ow_crc8(scratch, 8);
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if (crc != scratch[8])
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{
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printf("%s: crc check failed for device %d, returning previously "
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"measured temperature\n", __FUNCTION__, index);
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return dev->devices[index].temperature;
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}
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// check the sign bit(s)
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bool negative = (scratch[1] & 0x80) ? true : false;
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// shift everything into position
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int16_t temp = (scratch[1] << 8) | scratch[0];
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// grab the fractional
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uint8_t frac = temp & 0x0f;
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// depending on the resolution, some frac bits should be ignored, so
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// we mask them off. For 12bits, all bits are valid so we leve them
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// alone.
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switch (dev->devices[index].resolution)
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{
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case DS18B20_RESOLUTION_9BITS: frac &= 0x08; break;
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case DS18B20_RESOLUTION_10BITS: frac &= 0x0c; break;
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case DS18B20_RESOLUTION_11BITS: frac &= 0x0e; break;
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// use all bits for 12b
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case DS18B20_RESOLUTION_12BITS: break;
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}
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// remove the fractional with extreme prejudice
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temp >>= 4;
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// compensate for sign
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if (negative)
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temp -= 65536; // 2^^16
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// convert
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return ( (float)temp + ((float)frac * 0.0625) );
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}
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float ds18b20_get_temperature(const ds18b20_context dev, unsigned int index)
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{
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assert(dev != NULL);
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if (index >= dev->numDevices)
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{
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printf("%s: device index %d out of range\n", __FUNCTION__, index);
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return 0.0;
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}
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return dev->devices[index].temperature;
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}
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void ds18b20_set_resolution(const ds18b20_context dev, unsigned int index,
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DS18B20_RESOLUTIONS_T res)
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{
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assert(dev != NULL);
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if (index >= dev->numDevices)
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{
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printf("%s: device index %d out of range\n", __FUNCTION__, index);
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return;
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}
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static const int numScratch = 9;
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uint8_t scratch[numScratch];
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// read the 9-byte scratchpad
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_READ_SCRATCHPAD,
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dev->devices[index].id);
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int i;
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for (i=0; i<numScratch; i++)
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scratch[i] = (uint8_t)mraa_uart_ow_read_byte(dev->ow);
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// resolution is stored in byte 4
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scratch[4] = ((scratch[4] & ~(_DS18B20_CFG_RESOLUTION_MASK <<
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_DS18B20_CFG_RESOLUTION_SHIFT))
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| (res << _DS18B20_CFG_RESOLUTION_SHIFT));
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// now, write back, we only write 3 bytes (2-4), no cksum.
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_WRITE_SCRATCHPAD,
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dev->devices[index].id);
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for (i=0; i<3; i++)
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mraa_uart_ow_write_byte(dev->ow, scratch[i+2]);
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}
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void ds18b20_copy_scratch_pad(const ds18b20_context dev, unsigned int index)
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{
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assert(dev != NULL);
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if (index >= dev->numDevices)
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{
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printf("%s: device index %d out of range\n", __FUNCTION__, index);
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return;
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}
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// issue the command
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mraa_uart_ow_command(dev->ow, DS18B20_CMD_COPY_SCRATCHPAD,
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dev->devices[index].id);
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sleep(1); // to be safe...
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}
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void ds18b20_recallEEPROM(const ds18b20_context dev, unsigned int index)
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{
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assert(dev != NULL);
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if (index >= dev->numDevices)
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{
|
||||
printf("%s: device index %d out of range\n", __FUNCTION__, index);
|
||||
return;
|
||||
}
|
||||
|
||||
// issue the command
|
||||
mraa_uart_ow_command(dev->ow, DS18B20_CMD_RECALL_EEPROM,
|
||||
dev->devices[index].id);
|
||||
|
||||
// issue read timeslots until a '1' is read back, indicating completion
|
||||
while (!mraa_uart_ow_bit(dev->ow, 1))
|
||||
usleep(100);
|
||||
}
|
||||
|
||||
int ds18b20_devices_found(const ds18b20_context dev)
|
||||
{
|
||||
assert(dev != NULL);
|
||||
|
||||
return dev->numDevices;
|
||||
}
|
||||
|
||||
const uint8_t *ds18b20_get_id(const ds18b20_context dev, unsigned int index)
|
||||
{
|
||||
assert(dev != NULL);
|
||||
|
||||
if (index >= dev->numDevices)
|
||||
return NULL;
|
||||
|
||||
static uint8_t id[ROMCODE_SIZE];
|
||||
|
||||
memcpy(id, dev->devices[index].id, ROMCODE_SIZE);
|
||||
return id;
|
||||
}
|
||||
236
src/ds18b20/ds18b20.h
Normal file
236
src/ds18b20/ds18b20.h
Normal file
@ -0,0 +1,236 @@
|
||||
/*
|
||||
* Author: Jon Trulson <jtrulson@ics.com>
|
||||
* Copyright (c) 2016 Intel Corporation.
|
||||
*
|
||||
* Permission is hereby granted, free of charge, to any person obtaining
|
||||
* a copy of this software and associated documentation files (the
|
||||
* "Software"), to deal in the Software without restriction, including
|
||||
* without limitation the rights to use, copy, modify, merge, publish,
|
||||
* distribute, sublicense, and/or sell copies of the Software, and to
|
||||
* permit persons to whom the Software is furnished to do so, subject to
|
||||
* the following conditions:
|
||||
*
|
||||
* The above copyright notice and this permission notice shall be
|
||||
* included in all copies or substantial portions of the Software.
|
||||
*
|
||||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
||||
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
|
||||
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
||||
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
|
||||
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
|
||||
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
|
||||
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
|
||||
*/
|
||||
#pragma once
|
||||
|
||||
#include <stdlib.h>
|
||||
#include <unistd.h>
|
||||
#include <string.h>
|
||||
|
||||
#include <mraa/uart_ow.h>
|
||||
|
||||
#include "upm.h"
|
||||
|
||||
#ifdef __cplusplus
|
||||
extern "C" {
|
||||
#endif
|
||||
|
||||
// The family code for these devices. We handle all of them that
|
||||
// are found on the bus.
|
||||
#define DS18B20_FAMILY_CODE 0x28
|
||||
|
||||
/**
|
||||
* @library ds18b20
|
||||
* @sensor ds18b20
|
||||
* @comname DS18B20 1-Wire Temperature Sensor
|
||||
* @type uart
|
||||
* @man maxim
|
||||
* @con uart
|
||||
* @web https://www.sparkfun.com/products/11050
|
||||
*
|
||||
* @brief DS18B20 1-Wire Temperature Sensor
|
||||
*
|
||||
* This driver supports, and was tested with, a DS18B20 with
|
||||
* external power.
|
||||
*
|
||||
* Multiple DS18B20 devices can be connected to this bus. This
|
||||
* module will identify all such devices connected, and allow you
|
||||
* to access them using an index starting at 0.
|
||||
*
|
||||
* Parasitic power is not currently supported due
|
||||
* to the very tight 10us limit on switching a GPIO properly to
|
||||
* supply power during certain operations. For this reason, you
|
||||
* should use external power for your sensors.
|
||||
*
|
||||
* Setting the alarm values (Tl, Th) is also not supported, since
|
||||
* this is only useful when doing a 1-wire device search looking
|
||||
* for devices in an alarm state, a capability not yet supported
|
||||
* in MRAA. In reality, this is trivial to handle yourself in
|
||||
* your application.
|
||||
*
|
||||
* This device requires the use of a TTL level UART (specifically
|
||||
* through the uart_ow MRAA context) to provide access to a Dallas
|
||||
* 1-wire bus. It is important to realize that the UART is only
|
||||
* being used to provide an interface to devices on a Dallas 1-wire
|
||||
* compliant bus.
|
||||
*
|
||||
* A circuit like the following should be used for the UART
|
||||
* interface (ASCII schematic - best viewed in a fixed monospace
|
||||
* font):
|
||||
*
|
||||
* -|
|
||||
* U| (D1)
|
||||
* A| TX---|<--+
|
||||
* R| |
|
||||
* T| RX-------o--------o >to 1-wire data bus
|
||||
* -|
|
||||
*
|
||||
*
|
||||
* Vcc
|
||||
* |
|
||||
* o------------+
|
||||
* | |
|
||||
* R1 |
|
||||
* | o(+)
|
||||
* >1-wire------o--------o[DS18B20]
|
||||
* o(-)
|
||||
* |
|
||||
* GND
|
||||
*
|
||||
* D1 = 1N4148
|
||||
* R1 = 4.7K
|
||||
*
|
||||
* The cathode of D1 is connected to the UART TX.
|
||||
*
|
||||
* @snippet ds18b20.c Interesting
|
||||
*/
|
||||
|
||||
// forward declaration
|
||||
typedef struct _ds18b20_info_t ds18b20_info_t;
|
||||
|
||||
/**
|
||||
* Device context
|
||||
*/
|
||||
typedef struct _ds18b20_context {
|
||||
mraa_uart_ow_context ow;
|
||||
|
||||
// number of devices found
|
||||
int numDevices;
|
||||
|
||||
// list of allocated ds18b20_info_t instances
|
||||
ds18b20_info_t *devices;
|
||||
} *ds18b20_context;
|
||||
|
||||
// commands
|
||||
typedef enum {
|
||||
DS18B20_CMD_CONVERT = 0x44, // start a temp conversion
|
||||
DS18B20_CMD_WRITE_SCRATCHPAD = 0x4e,
|
||||
DS18B20_CMD_READ_SCRATCHPAD = 0xbe,
|
||||
DS18B20_CMD_COPY_SCRATCHPAD = 0x48, // copy scratchpad to EEPROM
|
||||
DS18B20_CMD_RECALL_EEPROM = 0xb8, // copy EEPROM to scratchpad
|
||||
DS18B20_CMD_READ_POWER_SUPPLY = 0xb4 // parasitically powered?
|
||||
} DS18B20_CMD_T;
|
||||
|
||||
// config register (scratchpad[4])
|
||||
typedef enum {
|
||||
DS18B20_CFG_RESOLUTION_R0 = 0x20,
|
||||
DS18B20_CFG_RESOLUTION_R1 = 0x40,
|
||||
_DS18B20_CFG_RESOLUTION_MASK = 3,
|
||||
_DS18B20_CFG_RESOLUTION_SHIFT = 5
|
||||
|
||||
// all other bits reserved and non-writable
|
||||
} DS18B20_CFG_BITS_T;
|
||||
|
||||
typedef enum {
|
||||
DS18B20_RESOLUTION_9BITS = 0, // 93.75ms (tconv/8)
|
||||
DS18B20_RESOLUTION_10BITS = 1, // 187.5 (tconv/4)
|
||||
DS18B20_RESOLUTION_11BITS = 2, // 375ms (tconv/2)
|
||||
DS18B20_RESOLUTION_12BITS = 3 // 750ms (tconv)
|
||||
} DS18B20_RESOLUTIONS_T;
|
||||
|
||||
/**
|
||||
* This function will initilaize and search the 1-wire bus and store
|
||||
* information on each DS18B20 device detected on the bus. If no
|
||||
* devices are found, NULL is returned. Once this function
|
||||
* completes successfully, you can use ds18b20_devices_found() to
|
||||
* determine how many devices were detected.
|
||||
*
|
||||
* @return device context, or NULL on error.
|
||||
*/
|
||||
ds18b20_context ds18b20_init(unsigned int uart);
|
||||
|
||||
/**
|
||||
* Close the device and deallocate all resources.
|
||||
*/
|
||||
void ds18b20_close(ds18b20_context dev);
|
||||
|
||||
/**
|
||||
* Update our stored temperature for a device. This method must
|
||||
* be called prior to ds18b20_get_temperature().
|
||||
*
|
||||
* @param index The device index to access (starts at 0). Specify
|
||||
* -1 to query all detected devices. Default: -1
|
||||
*/
|
||||
void ds18b20_update(const ds18b20_context dev, int index);
|
||||
|
||||
/**
|
||||
* Get the current temperature. ds18b20_update() must have been
|
||||
* called prior to calling this method.
|
||||
*
|
||||
* @param index The device index to access (starts at 0).
|
||||
* @return The last temperature reading in Celsius.
|
||||
*/
|
||||
float ds18b20_get_temperature(const ds18b20_context dev,
|
||||
unsigned int index);
|
||||
|
||||
/**
|
||||
* Set the device resolution for a device. These devices support
|
||||
* 9, 10, 11, and 12 bits of resolution, with the default from the
|
||||
* factory at 12 bits.
|
||||
*
|
||||
* @param index The device index to access (starts at 0).
|
||||
* @param res One of the DS18B20_RESOLUTIONS_T values
|
||||
*/
|
||||
void ds18b20_set_resolution(const ds18b20_context dev, unsigned int index,
|
||||
DS18B20_RESOLUTIONS_T res);
|
||||
|
||||
/**
|
||||
* Copy the device's scratchpad memory to the EEPROM. This
|
||||
* includes the configuration byte (resolution).
|
||||
*
|
||||
* @param index The device index to access (starts at 0).
|
||||
*/
|
||||
void ds18b20_copy_scratchpad(const ds18b20_context dev, unsigned int index);
|
||||
|
||||
/**
|
||||
* Copy the device's EEPROM memory to the scratchpad. This method
|
||||
* will return when the copy completes. This operation is
|
||||
* performed by the device automatically on power up, so it is
|
||||
* rarely needed.
|
||||
*
|
||||
* @param index The device index to access (starts at 0).
|
||||
*/
|
||||
void ds18b20_recall_eeprom(const ds18b20_context dev, unsigned int index);
|
||||
|
||||
/**
|
||||
* This method will return the number of DS18B20 devices that were
|
||||
* found on the bus by ds18b20_init().
|
||||
*
|
||||
* @return number of DS18B20's that were found on the bus
|
||||
*/
|
||||
int ds18b20_devices_found(const ds18b20_context dev);
|
||||
|
||||
/**
|
||||
* Return an 8 byte string representing the unique device ID (1-wire
|
||||
* romcode) for a given device index. The pointer returned is
|
||||
* statically allocated and will be overwritten on each call.
|
||||
*
|
||||
* @param index The device index to access (starts at 0).
|
||||
* @return pointer to 8 byte DS18B20_ROMCODE_T representing the 1-wire
|
||||
* device's unique romcode, or NULL on error.
|
||||
*/
|
||||
const uint8_t *get_id(const ds18b20_context dev, unsigned int index);
|
||||
|
||||
#ifdef __cplusplus
|
||||
}
|
||||
#endif
|
||||
@ -72,12 +72,39 @@ namespace upm {
|
||||
* in MRAA. In reality, this is trivial to handle yourself in
|
||||
* your application.
|
||||
*
|
||||
* This device requires the use of a UART to provide access to a
|
||||
* Dallas 1-wire bus, via a new facility supported by MRAA (once
|
||||
* the relevant PR is accepted), using the UartOW access class.
|
||||
* It is important to realize that the UART is only being used to
|
||||
* access and control a Dallas 1-wire compliant bus, it is not
|
||||
* actually a UART device.
|
||||
* This device requires the use of a TTL level UART (specifically
|
||||
* through the UartOW MRAA context class) to provide access to a
|
||||
* Dallas 1-wire bus. It is important to realize that the UART is
|
||||
* only being used to provide an interface to devices on a Dallas
|
||||
* 1-wire compliant bus.
|
||||
*
|
||||
* A circuit like the following should be used for the UART
|
||||
* interface (ASCII schematic - best viewed in a fixed monospace
|
||||
* font):
|
||||
*
|
||||
* -|
|
||||
* U| (D1)
|
||||
* A| TX---|<--+
|
||||
* R| |
|
||||
* T| RX-------o--------o >to 1-wire data bus
|
||||
* -|
|
||||
*
|
||||
*
|
||||
* Vcc
|
||||
* |
|
||||
* o------------+
|
||||
* | |
|
||||
* R1 |
|
||||
* | o(+)
|
||||
* >1-wire------o--------o[DS18B20]
|
||||
* o(-)
|
||||
* |
|
||||
* GND
|
||||
*
|
||||
* D1 = 1N4148
|
||||
* R1 = 4.7K
|
||||
*
|
||||
* The cathode of D1 is connected to the UART TX.
|
||||
*
|
||||
* @snippet ds18b20.cxx Interesting
|
||||
*/
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user