Nrf24Gateway - a real nRF24L01+ radio bridged to the gateway

Layer: Foundation · Build flags: PC_ENABLE_NRF24, PC_ENABLE_GATEWAY

What this example teaches

A second radio driver plugged into the gateway - the cheap, ubiquitous Nordic nRF24L01+ 2.4 GHz module. It shows that a different bus shape drops into the same gateway: where the SX127x is plain register read/write, the nRF24 uses an SPI command protocol and a separate CE pin, so its nrf_bus carries an SPI transfer plus a CE callback.

nRF24 RX --SPI--> pc_nrf24_recv() -> pipe + payload -> pc_gateway_uplink(port, pipe, ...)
                                                           |
                                        envelope + topic  nrf24/0/<pipe>
                                                           |
                                                  northbound publish (MQTT/HTTP/WS)

The nRF24 does its own hardware addressing: a received frame's source is the pipe number it arrived on, so there is no in-payload header (no codec) - the pipe is the address handed to pc_gateway_uplink(). Payloads are a static width (PC_NRF24_PAYLOAD, default 32); a short send is zero-padded.

nrf_config cfg = {}; cfg.address = addr5; cfg.channel = 76; cfg.data_rate = 0; cfg.tx_power = 3;
pc_nrf24_init(&bus, &cfg);
pc_nrf24_set_rx(&bus);
 
uint8_t buf[PC_NRF24_PAYLOAD]; uint8_t pipe;
int n = pc_nrf24_recv(&bus, buf, sizeof(buf), &pipe);   // -> a frame, or -1
pc_gateway_uplink(0, pipe, buf, n, 0);                   // pipe = source address

Wiring (ESP32 <-> nRF24L01+)

nRF24	ESP32
SCK	GPIO 18
MISO	GPIO 19
MOSI	GPIO 23
CSN	GPIO 5
CE	GPIO 4
VCC	3V3
GND	GND

Change the PIN_* constants for your board (a 10 uF cap across VCC/GND helps the module's TX current spikes). It needs the module wired to actually receive - the SPI command protocol is host-tested in test/test_nrf24.

Build-flag note

The flags must reach the library build, so pass them as build flags:

pio ci --board=esp32dev --project-option="framework=arduino" \
  --project-option="build_flags=-DPC_ENABLE_NRF24=1 -DPC_ENABLE_GATEWAY=1" \
  --lib="." examples/Drivers/Nrf24Gateway/Nrf24Gateway.ino