Transmit number via ble

[Stas]

Hello! I have uint32_t adc_value (from external ADC converter) And try to send it value through ble. My code:

main.c: ....

 for (;;)
    {
	Weighing();
        power_manage();    			 
			if(adc_value)    				
			{
				SEGGER_RTT_printf(0, "%d\n", adc_value);
				ble_adc_send(&m_nus, &adc_value);
			}
			nrf_delay_ms(100);
    }

here's send value function from ble_nus.c:

uint32_t ble_adc_send(ble_nus_t * p_nus, uint32_t *adc_value)
{
    ble_gatts_hvx_params_t hvx_params;

    VERIFY_PARAM_NOT_NULL(p_nus);

    if ((p_nus->conn_handle == BLE_CONN_HANDLE_INVALID) || (!p_nus->is_notification_enabled))
    {
        return NRF_ERROR_INVALID_STATE;
    }
		uint16_t length = 10;
    if (length > BLE_NUS_MAX_DATA_LEN)
    {
        return NRF_ERROR_INVALID_PARAM;
    }
		
    memset(&hvx_params, 0, sizeof(hvx_params));

    hvx_params.handle = p_nus->rx_handles.value_handle;
    hvx_params.p_data = (uint8_t*) adc_value;
    hvx_params.p_len  = &length;
    hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;

    return sd_ble_gatts_hvx(p_nus->conn_handle, &hvx_params);
}

1. Segger RTT terminal shows correct values but in mobile phone I getting garbage data. Notification works properly by the way.

2. What is the easiest way to convert int to string. Before working with 8-bit MC I used ultoa/utoa function from the lib with avg gcc compiler, here it's not working. But vice versa converting string to int (itoa) works good

Thanks

[AD1170]

Hello, the length of an uint32_t is 4 not 10. So you should use sizeof(uint32_t) to initialize the "length" variable. I think you want to convert the uint32_t ADC value on the receiver side. If you correct the length, your conversion with ultoa() should also work.

Regards

[Stas]

Thanks for answer. Actually I used length equals 4 , but the result was the same

[AD1170]

Can you provide a code snippet from the receiver side?

[Stas]

The receiver side is nrf connect app where I just read the characteristic value. Also I use my own simple android app just for read/write characteristics from ble. Both of them work properly with getting string like e.g via UART, but with number I've met some issues.

[AD1170]

Try the following:

...
uint8_t buffer[4];

uint16_t length = uint32_encode(*adc_value, buffer);
...
hvx_params.p_data = buffer;
hvx_params.p_len  = &length;
...

Take a look at uint32_encode() (app_util.h") to see how the bytes are ordered. In this way, the byte order is defined and you can reorder the bytes on the receiver side. If you dont know how, just ask.

[Stas]

uint32_t ble_adc_send(ble_nus_t * p_nus, uint32_t *adc_value) { ble_gatts_hvx_params_t hvx_params;

    VERIFY_PARAM_NOT_NULL(p_nus);

    if ((p_nus->conn_handle == BLE_CONN_HANDLE_INVALID) || (!p_nus->is_notification_enabled))
    {
        return NRF_ERROR_INVALID_STATE;
    }
		uint8_t buffer[4];
		uint16_t length = uint32_encode(*adc_value, buffer);
    if (length > BLE_NUS_MAX_DATA_LEN)
    {
        return NRF_ERROR_INVALID_PARAM;
    }
		
    memset(&hvx_params, 0, sizeof(hvx_params));

    hvx_params.handle = p_nus->rx_handles.value_handle;
    hvx_params.p_data = buffer;
    hvx_params.p_len  = &length;
    hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;

    return sd_ble_gatts_hvx(p_nus->conn_handle, &hvx_params);
}

just the same result.