esp_software_i2c's Introduction

Software I2C master for ESP-IDF (ESP32)

What?

ESP32 has only two hardware I2C ports. Sometimes you are already using both ports for I2C slaves but still need to have an I2C master. Bitbanging to the rescue!

Install

Install the library using by cloning it to the components folder of your ESP-IDF project.

$ cd components
$ git clone [email protected]:tuupola/esp-software-i2c.git

Usage

Software driver API mimics the original ESP-IDF hardware master API. Biggest difference is that there is no command link and instead of queuing commands are sent directly to the I2C bus. Example below reads SLAVE_DATA_LENGTH bytes from SLAVE_ADDRESS and dumps it to console. See tuupola/esp-examples for better example.

static const char *TAG = "sofware_i2c";

uint8_t *data_read = (uint8_t *) malloc(SLAVE_DATA_LENGTH);

sw_i2c_master_start();
sw_i2c_master_write_byte((SLAVE_ADDRESS << 1) | I2C_MASTER_READ);
if (SLAVE_DATA_LENGTH > 1) {
    sw_i2c_master_read(data_read, SLAVE_DATA_LENGTH - 1, ACK);
}
sw_i2c_master_read_byte(data_read + SLAVE_DATA_LENGTH - 1, NAK)
sw_i2c_master_stop();

ESP_LOG_BUFFER_HEXDUMP(TAG, data_read, SLAVE_DATA_LENGTH, ESP_LOG_INFO);}

Same code with the original ESP-IDF hardware API would be.

static const char *TAG = "hardware_i2c";

uint8_t *data_read = (uint8_t *) malloc(SLAVE_DATA_LENGTH);
i2c_cmd_handle_t cmd = i2c_cmd_link_create();

i2c_master_start(cmd);
i2c_master_write_byte(cmd, (SLAVE_ADDRESS << 1) | I2C_MASTER_READ, ACK_CHECK_ENABLE);
if (SLAVE_DATA_LENGTH > 1) {
    i2c_master_read(cmd, data_read, SLAVE_DATA_LENGTH - 1, ACK);
}
i2c_master_read_byte(cmd, data_read + SLAVE_DATA_LENGTH - 1, NAK)
i2c_master_stop(cmd);
i2c_master_cmd_begin(I2C_MASTER_NUM, cmd, 1000 / portTICK_RATE_MS);
i2c_cmd_link_delete(cmd);

ESP_LOG_BUFFER_HEXDUMP(TAG, data_read, SLAVE_DATA_LENGTH, ESP_LOG_INFO);