Transmiting only slave address on TWI I2C

RE: Transmiting only slave address on TWI I2C

mojangeex — Mon, 18 Nov 2019 12:15:46 GMT

Sorry for late response.

Thank you for response.

     uint8_t dra[0] ={};
     err_code = nrf_drv_twi_tx(&m_twi, 0xE1,dra,1,false);
      APP_ERROR_CHECK(err_code);

Application does not crash with above code, but I2C device still does not work. I will investigate further and report when I solve it.
Best regards.

RE: Transmiting only slave address on TWI I2C

bjorn-spockeli — Tue, 12 Nov 2019 15:00:26 GMT

Fatal Error means that the nrf_drv_twi_tx has returned a non-zero error code and this is being caught by the APP_ERROR_CHECK call. Which return code is nrf_drv_twi_tx returning? You should be able to see this when debugging the application. My guess it that its NRF_ERROR_INVALID_PARAM, i.e. 0x07. If that is the case then try passing an empty buffer instead of a NULL pointer.

RE: Transmiting only slave address on TWI I2C

mojangeex — Tue, 12 Nov 2019 09:37:18 GMT

Hello
I am running SDK 15.3 and nRF52832 DK.

Code compiles sucessfully, but the program crashes at executing that line.

err_code = nrf_drv_twi_tx(&m_twi, 0xE1,NULL,0,true);
APP_ERROR_CHECK(err_code);

<00> error> app: Fatal error

00> warning> app: System reset

I need to send message without data frame.

On arduino there is an example:

 Wire.beginTransmission((uint8_t)_i2caddr);
    Wire.write((uint8_t)reg); //This send the command to get data
    Wire.write(0x0);
    Wire.write(0x0);
    Wire.write(0x0);
    Wire.write(0x0);
    Wire.write(0x0);
    Wire.endTransmission();
    
    Wire.beginTransmission(0xE1);
    Wire.endTransmission();

RE: Transmiting only slave address on TWI I2C

bjorn-spockeli — Tue, 12 Nov 2019 08:30:44 GMT

HI mojoangeex,

I do not think you can send only the address as message going out on the bus will need to contain the following:

Start condition
Stop condition
Read and write bits
ACK/NACK bits
Address of the Slave
Data frame

Which SDK version are you using and which nRF device is it running on? Does nrf_drv_twi_tx( return an error code? If so, which? It could be that you have to point to an empty buffer rather than passing a NULL pointer.

err_code = nrf_drv_twi_tx(&m_twi, 0xE1,NULL,0,true);
APP_ERROR_CHECK(err_code);

Best regards

Bjørn