178 lines
7.6 KiB
Markdown
178 lines
7.6 KiB
Markdown
# esp-idf-mirf
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A port of the Mirf library for ESP-IDF.
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The library provides basic control of the Nordic nRF24L01/nRF24L01+ RF modules.
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I ported from [here](https://github.com/nopnop2002/Arduino-STM32-nRF24L01).
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# Software requirements
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ESP-IDF V4.4/V5.x.
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ESP-IDF V5.0 is required when using ESP32-C2.
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ESP-IDF V5.1 is required when using ESP32-C6.
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# Installation
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```Shell
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git clone https://github.com/nopnop2002/esp-idf-mirf
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cd esp-idf-mirf/Peer-to-peer
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idf.py set-target {esp32/esp32s2/esp32s3/esp32c2/esp32c3/esp32c6}
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idf.py menuconfig
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idf.py flash
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```
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__Note for ESP32C3__
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For some reason, there are development boards that cannot use GPIO06, GPIO08, GPIO09, GPIO19 for SPI clock pins.
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According to the ESP32C3 specifications, these pins can also be used as SPI clocks.
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I used a raw ESP-C3-13 to verify that these pins could be used as SPI clocks.
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# Configuration for Transceiver
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__Note for Channel__
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Channels range from 0 to 127.
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The channel number of the sender and receiver must be the same.
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Channel = 0 uses the frequency of 2.4000GHz, channel = 127 uses the frequency of 2.4127GHz.
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The width of one channel is only 0.01GHz.
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Using multiple radio node at the same time will almost always cause interference, even if you change channels.
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# SPI BUS selection
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The ESP32 series has three SPI BUSs.
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SPI1_HOST is used for communication with Flash memory.
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You can use SPI2_HOST and SPI3_HOST freely.
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When you use SDSPI(SD Card via SPI), SDSPI uses SPI2_HOST BUS.
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When using this module at the same time as SDSPI or other SPI device using SPI2_HOST, it needs to be changed to SPI3_HOST.
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When you don't use SDSPI, both SPI2_HOST and SPI3_HOST will work.
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Previously it was called HSPI_HOST / VSPI_HOST, but now it is called SPI2_HOST / SPI3_HOST.
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# Using Advanced Settings
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When used at long distances, lowering the RF data rate stabilizes it.
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When changing the RF data rate, the sender and receiver must have the same value.
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When using 250KBps, it takes time to PAYLOAD sending and ACK PACKET receiving, so it is necessary to increase the automatic retransmission delay.
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I tested it with [this](https://github.com/nopnop2002/Arduino-STM32-nRF24L01/tree/master/example/AdvancedSetting).
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__If you want to initialize the nRF24L01 settings after using the Advanced Settings, you need to power cycle the nRF24L01 before executing.__
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Because nRF24L01 remembers the previous setting.
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nRF24L01 does not have Software Reset function.
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# Wirering
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|nRF24L01||ESP32|ESP32-S2/S3|ESP32-C2/C3/C6||
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|:-:|:-:|:-:|:-:|:-:|:-:|
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|MISO|--|GPIO19|GPIO37|GPIO4|(*1)|
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|SCK|--|GPIO18|GPIO36|GPIO3|(*1)|
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|MOSI|--|GPIO23|GPIO35|GPIO2|(*1)|
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|CE|--|GPIO16|GPIO34|GPIO1|(*1)|
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|CSN|--|GPIO17|GPIO33|GPIO0|(*1)|
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|GND|--|GND|GND|GND||
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|VCC|--|3.3V|3.3V|3.3V||
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(*1)You can change it to any pin using menuconfig.
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# Communicat with Arduino Environment
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I used [this](https://github.com/nopnop2002/Arduino-STM32-nRF24L01) library on Arduino environment.
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__You need to match the payload size and channel with Arduino and esp-idf.__
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- Arduino environment
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```C++
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Mirf.payload = sizeof(mydata.value);
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Mirf.channel = 90;
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Mirf.config();
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```
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- esp-idf
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```C
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uint8_t payload = sizeof(value);
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uint8_t channel = 90;
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Nrf24_config(&dev, channel, payload);
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```
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# Communicat with Raspberry Pi
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I used [this](https://github.com/nopnop2002/Raspberry-Mirf) library on Raspberry Pi.
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# Using binary data
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nRF24L01 is not interested in the contents of the payload.
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Therefore, nRF24L01 can send and receive binary data.
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But the internal format of the binary data depends on the MCU architecture, so communication between different architectures is not possible.
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If you want to send or receive binary data between different architectures, you need to encode it into a CSV format string like this.
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```123,-123,1234.5,-1234.5```
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nRF24L01 can send and receive up to 32 characters, but by adding an index to the sent data, it can send and receive 256 types of data.
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# Important
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When changing the settings of the nRF24L01, it is necessary to power cycle the nRF24L01 before executing.
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Because nRF24L01 remembers the previous setting.
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nRF24L01 does not have Software Reset function.
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# Enhanced ShockBurst features
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nRF24L01 has "Enhanced ShockBurst" features.
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"Enhanced ShockBurst" automatically sets the PTX(=Transmitter) in receive mode to wait for the ACK packet from PRX(=Receiver).
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## Transmission Successful
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|ESP32||nRF24L01[PTX]||nRF24L01[PRX]||ESP32|
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|:-:|:-:|:-:|:-:|:-:|:-:|:-:|
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|ESP32|-->|nRF24L01|||||
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|||nRF24L01|--(Payload Packet)-->|nRF24L01|||||
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||||wait 250uS||||||
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|||nRF24L01|<--(Ack Packet)--|nRF24L01|||||
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|ESP32|<--|nRF24L01|||||||
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|||||nRF24L01|-->|ESP32|
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## Transmission Failure
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PTX waits for an ACK packet for 250uS and retransmits 3 times.
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|ESP32||nRF24L01[PTX]||nRF24L01[PRX]||ESP32|
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|ESP32|-->|nRF24L01|||||
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|||nRF24L01|--(Payload Packet)-->|nRF24L01|||||
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||||wait 250uS||||||
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|||nRF24L01|--(Payload Packet)-->|nRF24L01|||||
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||||wait 250uS||||||
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|||nRF24L01|--(Payload Packet)-->|nRF24L01|||||
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||||wait 250uS||||||
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|ESP32|<--|nRF24L01|||||||
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Using a data rate of 250KBps extends the range of radio waves.
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However, it takes time to send PAYLOAD and receive ACK PACKET.
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Therefore, the delay time for automatic retransmission should be longer than 250uS.
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If the delay of automatic retransmission is not increased, it is considered as a transmission failure.
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|ESP32||nRF24L01[PTX]||nRF24L01[PRX]||ESP32|
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|:-:|:-:|:-:|:-:|:-:|:-:|:-:|
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|ESP32|-->|nRF24L01|||||
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|||nRF24L01|--(Payload Packet)-->|nRF24L01|||||
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||||Over 250uS||||||
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|||nRF24L01|<--(Ack Packet)--|nRF24L01|||||
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|ESP32|<--|nRF24L01|||||||
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|||||nRF24L01|-->|ESP32|
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See the data sheet for details on Enhanced ShockBurst.
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# Throughput
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spi_device_transmit is executed by the SPI driver and consumes 1tick of CPU time.
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When DMA is enabled, SPI max_transfer_sz defaults to 4092(4K).
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This indicates that 4092 bytes of data can be sent in 1tick(10 millsec).
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Therefore, the SPI transmission potential of ESP-IDF is 400Kbytes/Sec.
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This has a significant impact on the nRF24L01, which has a small maximum payload size.
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Unfortunately, nRF24L01's maximum payload size is 32 bytes.
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1 tick (10 millsec) is required to send payload and receive ack packet.
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This has nothing to do with SPI bus speed.
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The throughput of nRF24L01 is 32 bytes/10 millsec(=3,200 bytes/sec).
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RF data rate of nRF24L01 affects the radio range, but not the throughput.
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# About Si24R1 clone
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Si24R1 is marketed as a nRF24L01 compatible.
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__Si24R1 clone cannot send and receive correctly.__
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After purchasing the nRF24L01, be sure to check the markings on the chip.
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Many suppliers sell Si24R1 as nRF24L01.
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