ESP32: SPI Slave

ESP32 を SPI のスレーブとして使うサンプルです。

Raspberry Pi 4 をマスターとして、テストをしました。

プログラム

slave_calc.ino

// ---------------------------------------------------------------------
/*
	slave_calc/slave_calc.ino

						Jun/25/2025
*/
// ---------------------------------------------------------------------
#include "driver/spi_slave.h"
#include "driver/gpio.h"
#define	PROGRAM	"slave_calc.ino"
#define	VERSION	"2025-06-26 PM 13:40"

#define PIN_MOSI  23
#define PIN_MISO  19
#define PIN_SCLK  18
#define PIN_CS    5

uint8_t recv_buf[1];
uint8_t send_buf[1];

// ---------------------------------------------------------------------
void setup() {
	Serial.begin(115200);
	delay(1000);
	Serial.println("*** start ***");

	Serial.println("SPI Slave init");

	// SPIスレーブ設定
spi_slave_interface_config_t slave_config = {
	.spics_io_num = PIN_CS,
	.flags = 0,
	.queue_size = 1,
	.mode = 0,
	.post_setup_cb = NULL,
	.post_trans_cb = NULL
};

	spi_slave_transaction_t t;
	memset(&t, 0, sizeof(t));

	// SPIピン設定
	spi_bus_config_t bus_config = {
		.mosi_io_num = PIN_MOSI,
		.miso_io_num = PIN_MISO,
		.sclk_io_num = PIN_SCLK,
		.quadwp_io_num = -1,
		.quadhd_io_num = -1,
		.max_transfer_sz = 1
	};

	// バスとデバイス初期化
	esp_err_t ret;
	ret = spi_slave_initialize(HSPI_HOST, &bus_config, &slave_config, SPI_DMA_DISABLED);
	assert(ret == ESP_OK);

	delay(1000);
	Serial.println(PROGRAM);
	Serial.println(VERSION);
	Serial.println("*** setup end ***");
}

// ---------------------------------------------------------------------
void loop() {
	spi_slave_transaction_t t;
	memset(&t, 0, sizeof(t));

	t.length = 8;	// 8 bits
	t.rx_buffer = recv_buf;
	t.tx_buffer = send_buf;

	esp_err_t ret = spi_slave_transmit(HSPI_HOST, &t, portMAX_DELAY);

	if (ret == ESP_OK) {
		uint8_t received = recv_buf[0];
		send_buf[0] = received + 5;
		Serial.printf("Received: 0x%02X -> Respond: 0x%02X\n", received, send_buf[0]);
	}
}

// ---------------------------------------------------------------------

Raspberry Pi のプログラム

master.c

// ------------------------------------------------------------
//	master.c
//
// ------------------------------------------------------------
#include <bcm2835.h>
#include <stdio.h>
// ------------------------------------------------------------
void send_read_proc(uint8_t send_data)
{
	uint8_t read_data = bcm2835_spi_transfer(send_data);
	printf("Sent to SPI: 0x%02X. Read back from SPI: 0x%02X.\n", send_data, read_data);

}

// ------------------------------------------------------------
int main(int argc, char **argv)
{
	if (!bcm2835_init())
		return 1;
	bcm2835_spi_begin();
	bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST);	  // The default
	bcm2835_spi_setDataMode(BCM2835_SPI_MODE0);				   // The default
	bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_65536); // The default
	bcm2835_spi_chipSelect(BCM2835_SPI_CS0);					  // The default
	bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS0, LOW);	  // the default

	uint8_t send_data[] = {0x30,0x31,0x32,0x33,0x34,0x35,0x36};

	send_read_proc(send_data[0]);

	bcm2835_spi_end();
	bcm2835_close();
	return 0;
}

// ------------------------------------------------------------

Makefile

master: master.c
	gcc -o master master.c -l bcm2835
clean:
	rm -f master

実行結果

Raspberry Pi

$ sudo ./master 
Sent to SPI: 0x30. Read back from SPI: 0x35.