NRF_DRV_ADC_DEFAULT_CHANNEL compiling error

Question

Hi,
When compiling my program on SEGGER embedded studio I get the error: 
 Compiling ‘main.c’
 main.c
 expected expression before '{' token
 in expansion of macro 'NRF_DRV_ADC_DEFAULT_CHANNEL'
 
 In the code: 
 #define ADC_RIGHT	ADC_CONFIG_PSEL_AnalogInput2
 #define ADC_DOWN	ADC_CONFIG_PSEL_AnalogInput3
 #define ADC_LEFT	ADC_CONFIG_PSEL_AnalogInput4
 #define ADC_UP	ADC_CONFIG_PSEL_AnalogInput5
 
 uint32_t SSW_LIST[4] = { ADC_RIGHT, ADC_DOWN, ADC_LEFT, ADC_UP };

static void adc_config(nrf_drv_adc_channel_t channel)
{
 ret_code_t ret_code;
 nrf_drv_adc_config_t config = NRF_DRV_ADC_DEFAULT_CONFIG;

 ret_code = nrf_drv_adc_init(&config, adc_event_handler);
 APP_ERROR_CHECK(ret_code);

 nrf_drv_adc_channel_enable(&channel);
}
 
int main(void)
{
 uint32_t err_code;
 bool erase_bonds;

 // Initialize.
 APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);
 uart_init();

 buttons_leds_init(&erase_bonds);
 ble_stack_init();
 gap_params_init();
 services_init();
 advertising_init();
 conn_params_init();

 printf("
UART Start!
");
 err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
 APP_ERROR_CHECK(err_code);

 // Enter main loop.
 for (;;)
 {
 uint32_t i;
 int j = 0;
 for (i = 0; i < ADC_BUFFER_SIZE; i++)
 {
 nrf_adc_config_input_t channel = SSW_LIST[j];
 adc_config(NRF_DRV_ADC_DEFAULT_CHANNEL(channel)); // error in this line
 APP_ERROR_CHECK(nrf_drv_adc_buffer_convert(adc_buffer,ADC_BUFFER_SIZE));
 if(j==3)
 j = 0;
 else
 j++;

 if(send_flag){
 uint32_t err_code;
 char snum[5];
 itoa(adc_buffer[i], snum, 10);
 err_code = ble_nus_string_send(&m_nus, snum, 5);
 }
 power_manage();
 nrf_delay_ms(SAMPLING_PERIOD);
 }
 }
}
 
 on the last line. 
 The same program compiled on Keil gives this error: 
 ..\..\..\main.c(660): error: #29: expected an expression
 adc_config(
RF_DRV_ADC_DEFAULT_CHANNEL(SSW_LIST[j]));
 
 The function adc_config is the same as SDK V12 adc example
thanks a lot

Jørgen Holmefjord · Accepted Answer

Hi, 
 I'm not sure what you are trying to do in your code, but there are multiple problems. You should pass the adc input to the adc_config() function instead of NRF_DRV_ADC_DEFAULT_CHANNEL(channel) : 
 static void adc_config(nrf_adc_config_input_t input)
{
 ret_code_t ret_code;
 nrf_drv_adc_config_t config = NRF_DRV_ADC_DEFAULT_CONFIG;

 ret_code = nrf_drv_adc_init(&config, adc_event_handler);
 APP_ERROR_CHECK(ret_code);

 nrf_drv_adc_channel_t channel_config = NRF_DRV_ADC_DEFAULT_CHANNEL(input)
 nrf_drv_adc_channel_enable(&channel_config);
}
 
 Another problem is that you cannot call nrf_drv_adc_init() if the ADC driver is already initialized. You are now calling this function ADC_BUFFER_SIZE times. You will have to split this into two separate functions, or integrate the channel loop into your adc_config() function. It is not a good idea to put the ADC configuration inside a loop, unless you are uninitializing it somewhere. This will cause errors when the loop starts over again. 
 Best regards, 
 Jøgen