i2c_master_cmd_begin() returns ESP_FAIL

[adi_1234]

Hello,
i am trying to read time from the rtc - PCF85263ATT, so i start with writing the write-slave-address (0xA2) and the register to start reading from (seconds register 0x1) and i get NACK (as it shows on the oscilloscope). This NACK causes the failure of i2c_master_cmd_begin() with ESP_FAIL error.
scl pin is set to 18, sda is pin 19, i2c_port is I2C_NUM_0.

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here is the code:

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1.  
2. #define PCF85263ATT_SLAVE_REG_WRITE 0xA2
3. #define PCF85263ATT_SLAVE_REG_READ 0xA3
4. #define  PCF85263ATT_REG_SECONDS  0x01
5.  
6. typedef struct RtcDriver {
7.     int sda_pin_num;
8.     int scl_pin_num;
9.     i2c_port_t i2c_port;
10. } RtcDriver;
11.  
12.  
13. esp_err_t rtc_driver_init(RtcDriver* rtc_driver) {
14.     i2c_config_t conf = {
15.     .mode = I2C_MODE_MASTER,
16.     .sda_io_num = rtc_driver->sda_pin_num,        
17.     .sda_pullup_en = GPIO_PULLUP_DISABLE,  //there are pullup resistors in the circuit
18.     .scl_io_num = rtc_driver->scl_pin_num,        
19.     .scl_pullup_en = GPIO_PULLUP_DISABLE,  //there are pullup resistors in the circuit
20.     .master.clk_speed = 400000,  
21.     };
22.     esp_err_t err;
23.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_driver_install(rtc_driver->i2c_port, I2C_MODE_MASTER, I2C_MASTER_RX_BUF_DISABLE, I2C_MASTER_TX_BUF_DISABLE, 0));
24.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_set_data_mode(rtc_driver->i2c_port, I2C_DATA_MODE_MSB_FIRST, I2C_DATA_MODE_MSB_FIRST));
25.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_param_config(rtc_driver->i2c_port, &conf));
26.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_set_timeout(rtc_driver->i2c_port, 9000 / portTICK_RATE_MS));
27.     return 0;
28. }
29.  
30. esp_err_t rtc_driver_get_time(RtcDriver* rtc_driver, uint8_t* sec, uint8_t* min, uint8_t* hour){
31.     i2c_cmd_handle_t cmd = NULL;
32.     cmd = i2c_cmd_link_create();
33.     if(cmd == NULL) {
34.         ESP_LOGI(TAG, "i2c_cmd_link_create failed!" );
35.     }
36.     uint8_t data[3];  
37.     data[0] = PCF85263ATT_SLAVE_REG_WRITE;
38.     data[1] = PCF85263ATT_REG_SECONDS;
39.     data[2] = PCF85263ATT_SLAVE_REG_READ;
40.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_start(cmd));
41.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_write_byte(cmd, data[0] , ACK_CHECK_DIS)); //slave addr
42.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_write_byte(cmd, data[1], ACK_CHECK_EN)); //start to read from sec rgstr
43.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_stop(cmd));
44.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_cmd_begin(rtc_driver->i2c_port, cmd, 1000 / portTICK_RATE_MS));
45.     i2c_cmd_link_delete(cmd);
46.     vTaskDelay(100 / portTICK_RATE_MS);
47.     cmd = i2c_cmd_link_create();
48.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_start(cmd));
49.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_write(cmd, &data[2], 1, true));
50.     data[0] = 0;
51.     data[1] = 0;
52.     data[2] = 0;
53.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_read(cmd, &data[0], sizeof(data) ,I2C_MASTER_LAST_NACK));
54.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_stop(cmd));
55.     esp_err_t err;
56.     ESP_ERROR_CHECK_WITHOUT_ABORT(i2c_master_cmd_begin(rtc_driver->i2c_port, cmd, 1000 / portTICK_RATE_MS));
57.     i2c_cmd_link_delete(cmd);
58.     return 0;
59. }

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The second call to i2c_master_cmd_begin() returns ESP_ERR_TIMEOUT.
here is the datasheet of the rtc: https://www.nxp.com/docs/en/data-sheet/PCF85263A.pdf

What am i doing wrong?
i really wish to figure out why the rtc won't ack and why do i get ESP_ERR_TIMEOUT on the second call to i2c_master_cmd_begin().

Thank You,
Adi

[kalpanavengala]

Hi,
I have seen your code, maybe in line 41, the third parameter in the i2c_master_write_byte as ACK_CHECK_EN. If you are disabling the acknowledge check condition if the slave sends the NACK master will not check the condition and it will not enable the I2C_NACK_INTR maybe that is the cause to get the failure.