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ds18b20: Add a C implementation and inprove documentation

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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
2016-09-13 11:27:27 -06:00
committed by Noel Eck
parent 5088ee99e6
commit 6d437c8007
6 changed files with 756 additions and 11 deletions
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39
src/ds18b20/ds18b20.hpp
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@ -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
*/