Problem to generate modulated countiuous signal

[fabio soares]

Hi everyone! I'm trying to generate a modulated continuous signal in a specific channel using nrf52832. I used a code made from radio_test example that follows. The problem is that at the laboratory I'm contact with they couldn't find any signal, I don't have an osciloscope to try it, so I wanna know if it's possible to see by debbuging in Keil if it's sending something. If someone see a problem in the code or have any advise I'm greatful. Thanks.

#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include "bsp.h"
#include "nrf.h"
#include "radio_test.h"
#include "app_uart.h"
#include "app_error.h"
#include "nordic_common.h"

typedef enum
{
RADIO_TEST_NOP, /**< No test running. */
RADIO_TEST_TXCC, /**< TX constant carrier. */
RADIO_TEST_TXMC, /**< TX modulated carrier. */
RADIO_TEST_TXSWEEP, /**< TX sweep. */
RADIO_TEST_RXC, /**< RX constant carrier. */
RADIO_TEST_RXSWEEP, /**< RX sweep. */
} radio_tests_t;

#define BELL 7 // Bell

#define UART_TX_BUF_SIZE 512 /**< UART TX buffer size. */
#define UART_RX_BUF_SIZE 1 /**< UART RX buffer size. */

void uart_error_handle(app_uart_evt_t * p_event)
{
if (p_event->evt_type == APP_UART_COMMUNICATION_ERROR)
{
APP_ERROR_HANDLER(p_event->data.error_communication);
}
else if (p_event->evt_type == APP_UART_FIFO_ERROR)
{
APP_ERROR_HANDLER(p_event->data.error_code);
}
}

/** @brief Function for configuring all peripherals used in this example.
*/
static void init(void)
{
NRF_RNG->TASKS_START = 1;

// Start 16 MHz crystal oscillator
NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
NRF_CLOCK->TASKS_HFCLKSTART = 1;

// Wait for the external oscillator to start up
while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)
{
// Do nothing.
}
}

/** @brief Function for main application entry.
*/
int main(void)
{
while(true) {
uint8_t txpower = RADIO_TXPOWER_TXPOWER_0dBm; // 0 dBm
uint8_t mode = RADIO_MODE_MODE_Nrf_2Mbit; // 2 MBit mode
uint8_t channel = 40 // Transmit at channel 40
int delayms = 10;

init();
radio_modulated_tx_carrier(txpower, mode, channel);

}

}

/** @} */

[MartinBL]

Hi,

You have forgotten to actually start the radio. Try changing your code to something like this:

int main(void)
{ 
    uint8_t txpower = RADIO_TXPOWER_TXPOWER_0dBm; // 0 dBm
    uint8_t mode = RADIO_MODE_MODE_Nrf_2Mbit; // 2 MBit mode
    uint8_t channel = 40; // Transmit at channel 40
    int delayms = 10;
    init();
    radio_modulated_tx_carrier(txpower, mode, channel);
    
    NRF_RADIO->TASKS_START = 1;

    while(true) 
    { 
        ;
    }
    
}

Note that you shouldn't place all your code inside your while(true) loop. That will just restart your radio over and over again, and not transmit any measurable signals.

If you have an extra nRF52 DK kit you can use nRF Connect for desktop and the RSSI Viewer plugin to visualize the spectrum. After modifying your code my RSSI Viewer showed me this: