ESP32 Forum

Posted: **Wed Jul 09, 2025 3:27 pm**

Hello all,

I'm trying to convert some old I2C code (using i2c.h) to the new driver (using i2c_master.h) and I'm running into some issues I cannot explain. The old code works, but the new code panics and keeps crashing the device. I am sure I've overlooked something, but I've been staring at this for some days now and I just can't figure it out. Hopefully someone here can point out where the error is...

This is a very rudimentary bit of code for reading a touch controller, originally adapted from an Arduino example.

The code that works;

Code: Select all

#define I2C_SDA GPIO_NUM_2
#define I2C_SCL GPIO_NUM_1
const int i2c_touch_addr = 0x38;

bool init_i2c()
{
    i2c_config_t i2c_conf = {
        .mode = I2C_MODE_MASTER,
        .sda_io_num = I2C_SDA,
        .scl_io_num = I2C_SCL,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .master = {
            .clk_speed = 100000,
        },
        .clk_flags = I2C_SCLK_SRC_FLAG_FOR_NOMAL,
    };

    if (i2c_param_config(I2C_NUM_0, &i2c_conf) != ESP_OK)
    {
        return false;
    }

    if (i2c_driver_install(I2C_NUM_0, I2C_MODE_MASTER, 0, 0, 0) != ESP_OK)
    {
        return false;
    }

    return true;
}

int readTouchReg(uint8_t reg)
{
    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, i2c_touch_addr << 1 | I2C_MASTER_WRITE, ACK_CHECK_EN);
    i2c_master_write_byte(cmd, reg, I2C_MASTER_ACK);
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, (i2c_touch_addr << 1) | I2C_MASTER_READ, true);
    uint8_t result;
    i2c_master_read_byte(cmd, &result, I2C_MASTER_NACK);
    i2c_master_stop(cmd);
    i2c_master_cmd_begin(I2C_NUM_0, cmd, pdMS_TO_TICKS(1000));
    i2c_cmd_link_delete(cmd);
    return result;
}

And the new code that panics the device and makes it reboot forever;

Code: Select all

#define I2C_SDA GPIO_NUM_2
#define I2C_SCL GPIO_NUM_1
const int i2c_touch_addr = 0x38;
i2c_master_dev_handle_t touch_handle;
i2c_master_bus_handle_t bus_handle;

bool init_i2c()
{
    i2c_master_bus_config_t conf;
    conf.clk_source = I2C_CLK_SRC_DEFAULT;
    conf.i2c_port= I2C_NUM_0;
    conf.sda_io_num = I2C_SDA;
    conf.scl_io_num = I2C_SCL;
    conf.glitch_ignore_cnt = 7;
    conf.flags.enable_internal_pullup = GPIO_PULLUP_ENABLE;
    conf.intr_priority = 0;
    conf.trans_queue_depth = 10;

    if (i2c_new_master_bus(&conf, &bus_handle) != ESP_OK)
    {
        return false;
    }

    i2c_device_config_t touch_config;
    touch_config.dev_addr_length = I2C_ADDR_BIT_LEN_7;
    touch_config.device_address = i2c_touch_addr;
    touch_config.scl_speed_hz = 100000;

    if (i2c_master_bus_add_device(bus_handle, &touch_config, &touch_handle) != ESP_OK)
    {
        return false;
    }

    return true;
}

int readTouchReg(uint8_t reg)
{
    uint8_t result;
    uint8_t data[2] = {i2c_touch_addr, reg};
    //i2c_master_transmit(touch_handle, data, 2, 1000); // crash loops?
    i2c_master_transmit_receive(touch_handle, data, 2, &result, 1, 1000);
    return result;
}

I initially thought it was because of the buffer or something, but just doing a transmit has the same panic behaviour.

Can someone point out what I'm doing wrong here?

Thanks!

ESP32 Forum

Converting old I2C code to the new driver causes device to crash loop

Converting old I2C code to the new driver causes device to crash loop