esp32_i2c.ino

#include "driver/i2c.h"
#define DATA_LENGTH           512
#define RW_TEST_LENGTH        4
#define I2C_SLAVE_SCL_IO      5
#define I2C_SLAVE_SDA_IO      4
#define I2C_SLAVE_NUM         1

#define I2C_SLAVE_TX_BUF_LEN  (2 * DATA_LENGTH)
#define I2C_SLAVE_RX_BUF_LEN  (2 * DATA_LENGTH)
#define ESP_SLAVE_ADDR        0x33

uint8_t *data_wr = (uint8_t *)malloc(DATA_LENGTH);
uint8_t *data_rd = (uint8_t *)malloc(DATA_LENGTH);

static esp_err_t i2c_slave_init(void)
{
    i2c_port_t i2c_slave_port = (i2c_port_t)I2C_SLAVE_NUM;
    i2c_config_t conf_slave;
    conf_slave.sda_io_num = (gpio_num_t)I2C_SLAVE_SDA_IO;
    conf_slave.sda_pullup_en = GPIO_PULLUP_ENABLE;
    conf_slave.scl_io_num = (gpio_num_t)I2C_SLAVE_SCL_IO;
    conf_slave.scl_pullup_en = GPIO_PULLUP_ENABLE;
    conf_slave.mode = I2C_MODE_SLAVE;
    conf_slave.slave.addr_10bit_en = 0;
    conf_slave.slave.slave_addr = ESP_SLAVE_ADDR;
    esp_err_t err = i2c_param_config(i2c_slave_port, &conf_slave);
    if (err != ESP_OK) {
        printf("....... error to config ........\n");
        return err;
    }
    return i2c_driver_install(i2c_slave_port, conf_slave.mode, I2C_SLAVE_RX_BUF_LEN, I2C_SLAVE_TX_BUF_LEN, 0);
}

static void disp_buf(uint8_t *buf, int len)
{
    for (int i = 0; i < len; i++) {
        printf("%02x ", buf[i]);
        if ((i + 1) % 16 == 0) {
            printf("\n");
        }
    }
    printf("\n");
}

void setup() {
  Serial.begin(115200);
  delay(1000);
  int err = i2c_slave_init();
  if(err != 0){ 
    printf("init i2c error = %d\n",err);
  }
}

void loop() {
  i2c_port_t i2c_slave_port = (i2c_port_t)I2C_SLAVE_NUM;
  //check master write data
  int size = i2c_slave_read_buffer(i2c_slave_port, data_rd, RW_TEST_LENGTH, 1000 / portTICK_RATE_MS);
  printf("Slave read: [%d] bytes ----\n", size);
  //write buffer to master when needed
  size_t d_size = i2c_slave_write_buffer(i2c_slave_port, data_wr, RW_TEST_LENGTH, 1000 / portTICK_RATE_MS);
  if (d_size == 0) {
      printf("i2c slave tx buffer full\n");
  }
  delay(1000);
}