ESP32 Forum

Posted: **Fri Dec 02, 2022 4:51 pm**

Dear all,

I am trying to setup the bq24735 power management unit with ESP32-WROOM-32.

I have a problem with writing information to the BQ_CHARGE_OPTION_REG. Here is a recording from the logical analyzer:

: esp32.png (18.89 KiB) Viewed 825 times

The NACK is the problem. According to the datasheet write sequence should be this:

: datapacket.png (22.12 KiB) Viewed 825 times

Here is the code. The i2c_init(); happened successfully.

Code: [Select all] [Expand/Collapse]

#define     BQ_SLAVE_ADDR               0x12 >> 1
#define     BQ_CHARGE_OPTION_REG                0X12 >> 1
#define     I2C_MASTER_PORT                         I2C_NUM_0
#define     I2C_MASTER_TIMEOUT_MS           300
 
 
void app_main(void) {
 
    ESP_ERROR_CHECK(i2c_init());  //init is OK
 
    uint8_t chargeOption[3] = {BQ_CHARGE_OPTION_REG, 0xf9, 0x82};
 
    ESP_ERROR_CHECK(
            i2c_master_write_to_device(I2C_MASTER_PORT, BQ_SLAVE_ADDR, chargeOption, 3, I2C_MASTER_TIMEOUT_MS / portTICK_PERIOD_MS));
}

bq24735 datasheet:
https://www.ti.com/lit/ds/symlink/bq247 ... e.com%252F

Does anyone have a soolution to this? Or are there any bq libraries already implemented?

Posted: **Tue Dec 06, 2022 3:41 pm**

The problem is in i2c addressing. In this case the slave address has 7 bits and it is needed to be shifted so the write bit is 0. Command registers need not be shifted, but he slave address has to.

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