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SX1276/77/78/79 Low Power Long Range Transceiver driver for esp-idf

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esp-idf-sx127x

SX1276/77/78/79 Low Power Long Range Transceiver driver for esp-idf.

I based on this.

Changes from the original

  • Changed make to cmake.
  • Added support for ESP32S2, ESP32S3, ESP32C2, ESP32C3 and ESP32C6.
  • I left the control of CS to the driver.
  • Added a sample of ping-pong/http/mqtt.
  • Added some API functions.

Software requirements

ESP-IDF V4.4/V5.x.
ESP-IDF V5.0 is required when using ESP32-C2.
ESP-IDF V5.1 is required when using ESP32-C6.

Installation

git clone https://github.com/nopnop2002/esp-idf-sx127x
cd esp-idf-sx127x/basic/
idf.py set-target {esp32/esp32s2/esp32s3/esp32c2/esp32c3/esp32c6}
idf.py menuconfig
idf.py flash

Note for ESP32C3
For some reason, there are development boards that cannot use GPIO06, GPIO08, GPIO09, GPIO19 for SPI clock pins.
According to the ESP32C3 specifications, these pins can also be used as SPI clocks.
I used a raw ESP-C3-13 to verify that these pins could be used as SPI clocks.

Configuration for Transceiver

config-lora-1 config-lora-2

SPI BUS selection

config-lora-3

The ESP32 series has three SPI BUSs.
SPI1_HOST is used for communication with Flash memory.
You can use SPI2_HOST and SPI3_HOST freely.
When you use SDSPI(SD Card via SPI), SDSPI uses SPI2_HOST BUS.
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.
When you don't use SDSPI, both SPI2_HOST and SPI3_HOST will work.
Previously it was called HSPI_HOST / VSPI_HOST, but now it is called SPI2_HOST / SPI3_HOST.

Wirering

SX127X ESP32 ESP32-S2/S3 ESP32-C2/C3/C6
RST -- GPIO16 GPIO38 GPIO3
MISO -- GPIO19 GPIO37 GPIO4
SCK -- GPIO18 GPIO36 GPIO5
MOSI -- GPIO23 GPIO35 GPIO6
NSS -- GPIO15 GPIO34 GPIO7
GND -- GND GND GND
VCC -- 3.3V 3.3V 3.3V

You can change it to any pin using menuconfig.

Communication with SX126X

LoRa's packet format is strictly specified.
Therefore, if the following three parameters are the same, they can communicate with each other.

  • Signal Bandwidth (= BW)
  • Error Cording Rate (= CR)
  • Spreading Factor (= SF)

About communication speed and maximum reception sensitivity

In LoRa modulation mode, the communication speed (bps) and maximum reception sensitivity (RSSI) are determined by a combination of spreading factor (SF), bandwidth (BW), and coding rate (CDR).

  • SF
    SF (spreading factor) Increasing SF increases the spreading rate and improves noise resistance.
    This improves reception sensitivity and extends communication distance, but communication speed decreases.
  • BW
    Bandwidth sets the width of the communication band. Setting a larger bandwidth will improve communication speed.
    However, the radio reception sensitivity (RSSI) will decrease.
  • CDR
    CDR (CodingRate) sets the level of error correction rate.
    The larger the number, the better the correction rate, but the amount of information per packet increases.
    (No effect on maximum reception sensitivity)
    You can set whether to use Optimaise for each CDR, and enabling it will improve the correction rate, but will reduce communication speed.

Datasheet

Datasheet is here.

Reference

https://github.com/nopnop2002/esp-idf-sx126x