I2C stretching

[TomasCZ]

Hello guys, pls, is the I2C CLK STRETCHING set on or off by default ? I am trying to read the I2C OLED display data from external device but sometimes I receive slightly different data then it should be in comaprison with the data received by a Logic Analyzer. A frind of mine told me that it could be caused by I2C CLK strtching because the master device doesn't support stretching for sure. I sthere any way how to switch it off ? Something like I2C_SCL_STRETCH_CONF_REG &= ~1024;

This is my current code:

Code: Select all

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include "esp_log.h"
#include "driver/i2c.h"
#include "rom/gpio.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_timer.h"

static const char *TAG = "i2c-slave";

//#define LED_PIN 2

#define I2C_SLAVE_SCL_IO 22               /*!< gpio number for I2C master clock */
#define I2C_SLAVE_SDA_IO 21               /*!< gpio number for I2C master data  */
#define I2C_SLAVE_FREQ_HZ 100000        /*!< I2C master clock frequency */
#define I2C_SLAVE_TX_BUF_LEN 255                        /*!< I2C master doesn't need buffer */
#define I2C_SLAVE_RX_BUF_LEN 8192                           /*!< I2C master doesn't need buffer */
#define ESP_SLAVE_ADDR 0x3C

#define WRITE_BIT I2C_MASTER_WRITE              /*!< I2C master write */
#define READ_BIT I2C_MASTER_READ                /*!< I2C master read */
#define ACK_CHECK_EN 0x0                        /*!< I2C master will check ack from slave*/
#define ACK_CHECK_DIS 0x0                       /*!< I2C master will not check ack from slave */
#define ACK_VAL 0x1                             /*!< I2C ack value */
#define NACK_VAL 0x1                            /*!< I2C nack value */

#define portTICK_PERIOD_MS ( ( TickType_t ) ( 1000 / configTICK_RATE_HZ ) )
#define CONFIG_FREERTOS_HZ 1000

int i2c_slave_port = 1;
static esp_err_t i2c_slave_init(void)
{
  
    i2c_config_t conf_slave = {
    .sda_io_num = I2C_SLAVE_SDA_IO,          // select GPIO specific to your project
    .sda_pullup_en = GPIO_PULLUP_ENABLE,
    .scl_io_num = I2C_SLAVE_SCL_IO,          // select GPIO specific to your project
    .scl_pullup_en = GPIO_PULLUP_ENABLE,
    .mode = I2C_MODE_SLAVE,
    .slave.addr_10bit_en = 0,
    .slave.slave_addr = ESP_SLAVE_ADDR,      // address of your project
    .clk_flags = 0,
    };
    esp_err_t err = i2c_param_config(i2c_slave_port, &conf_slave);
    if (err != ESP_OK) {
        return err;
    }
    return i2c_driver_install(i2c_slave_port, conf_slave.mode, I2C_SLAVE_RX_BUF_LEN, I2C_SLAVE_TX_BUF_LEN, 0);
}

char * hex_bytes(size_t len, unsigned char * data)
{
	size_t reslen = len * 3 + 5;
	char * result = (char * ) malloc(reslen);
	char buf[5];
	result[0] = 0;
	
	for (int i = 0; i < len; i++)
	{
			snprintf(buf, 5, " %02X", data[i]);
			strcat(result, buf);
	}
	return result;
}

void app_main(void)
{
    uint8_t *received_data = (uint8_t *) malloc (I2C_SLAVE_RX_BUF_LEN);
    uint64_t prevTimeFifo = esp_timer_get_time();
    
    //uint8_t  received_data[I2C_SLAVE_RX_BUF_LEN] = {0};
    //uint8_t  on_command[] = "LED_ON";

    //gpio_pad_select_gpio(LED_PIN);
    //gpio_set_direction(LED_PIN, GPIO_MODE_OUTPUT);

    ESP_ERROR_CHECK(i2c_slave_init());
    ESP_LOGI(TAG, "I2C Slave initialized successfully");
    
    while(1)
    {
    int len = i2c_slave_read_buffer(i2c_slave_port, received_data, I2C_SLAVE_RX_BUF_LEN, 50 / portTICK_PERIOD_MS);

    

    if (len > 0)
    {
        received_data[len] = 0;
               
        char * str = hex_bytes(len, received_data);
        ESP_LOGI(TAG, "Received %s\n", str);
        free(str);

    }
    
    if ((esp_timer_get_time() - prevTimeFifo >= 2000000))
    {
        i2c_reset_rx_fifo(i2c_slave_port);
        //ESP_LOGI(TAG, "Fifo 2s");
        prevTimeFifo = esp_timer_get_time();
    }
    

    
    //ESP_LOGI(TAG, "Data Recived = %s", received_data);

    

    /*
    if(strncmp((const char*)received_data, "LED_ON", 6) == 0)
    {   
    ESP_LOGI(TAG, "Data Recived = %s", received_data);
    gpio_set_level(LED_PIN, 1);
    }
    else if(strncmp((const char*)received_data, "LED_OFF", 7) == 0)
    {
    ESP_LOGI(TAG, "Data Recived = %s", received_data);   
    gpio_set_level(LED_PIN, 0);
    }
    */

    //memset(received_data, 0, I2C_SLAVE_RX_BUF_LEN);
    }

}

[Andre_Cilia]

Hi TomasCZ,

Have you managed to find a solution to this problem?

Thanks and regards,
Andre

[TomasCZ]

Hi Andre, unfortuntaely not. We are trying to find different way and trying to write the code from beginning. But I am out off time now so the project is postponed.