How to transmit and receive beacons using nRF51 DK?

[BeaconBLE]

I need to transmit and receive beacons using nRF51 DK. I saw a few examples in the SDK ble_beacons where we use the app, but I need code to transmit and receive both using the nRF51 Development kit. Also, can you give me steps for setting up GCC for the nRF51DK, how do I setup that IDE for using it with the DK, if there are any youtube videos for setting up the GCC for the nRF51DK please send me the links. Also while receiving the beacons, I need the RSSI value at the receiver and how do I get that value?  Thank you so much for your help. Also, I need to know while transmitting from one nRF51DK to another is it necessary to pair the boards etc?

[MartinBL]

Hi,

I need code to transmit and receive both using the nRF51 Development kit.
First of all I think there is a misunderstanding regarding beacons. A BLE beacon is per definition not receiving anything. It is just mindlessly broadcasting a handful of bytes. If you want bidirectional communication between two nRF51 devices I suggest that you start out with the UART/Serial Port Emulation over BLE and Nordic UART Service Client examples. 

can you give me steps for setting up GCC for the nRF51DK
Unfortunately, we only have this relatively old tutorial: Development with GCC and Eclipse

I need the RSSI value at the receiver and how do I get that value? 
Please have a look at these APIs: sd_ble_gap_rssi_start(), sd_ble_gap_rssi_stop(), and sd_ble_gap_rssi_get().

I need to know while transmitting from one nRF51DK to another is it necessary to pair the boards etc?
It depends. But I suspect that you might be confusing BLE pairing and bonding.

 

[BeaconBLE]

Hello MartinBL,

First of all thank you so much for your help. I tried to execute the Nordic UART service Client on two dev boards, I programmed both the soft device and the hex file into both the boards ( I am not sure if I had to program both the boards with the same code but that's what I did) and both of those boards were advertising and not able to connect to each other. If you have any solution for that please let me know.

Also, I executed the radio transmitter and receiver example in the SDK, Its path is <InstallFolder>\examples\peripheral\radio\receiver and <InstallFolder>\examples\peripheral\radio\transmitter. My question is is there some sort of API I can use to get the RSSI or the signal strength on the receiver side because I think the API's that you mentioned above are for BLE and this application does not use BLE. So if you had something that would be really helpful for my project.

[MartinBL]

Hi,

BLE devices have various roles and you need both a Central and a Peripheral to make a link (See Ole Morten's comment here). This means that you cannot use the Nordic UART service Client example on both boards, but you need to use examples:

<InstallFolder>\ble_peripheral\ble_app_uart

on one board and

<InstallFolder>\examples\ble_central\ble_app_uart_c

on a different kits. The peripheral should then advertise and the central should scan. When the Central receives the advertising packets it will initiate the the connection. 

To get the RSSI you can read the RADIO->RSSISAMPLE register (Reading this register directly will not work if you are using a softdevice since the softdevice is restricting your applications access to the radio peripheral).

[BeaconBLE]

Hello,

First of all, while using the radio, I am not programming the soft device ( it was not there in the instructions on the infocenter page) and it is transmitting and receiving properly. How do I read the register as in what is the code for that? and if I cannot read it directly how should I go about it? 

[MartinBL]

Hi,

If you are not using a Softdevice you can read the register directly. For example like this: uint32_t rssi = NRF_RADIO->RSSISAMPLE;

To clarify, the Softdevice is Nordic's proprietary stack for BLE and ANT. If you use it, it will block and restrict access to certain peripherals as you can see in this list. 

[BeaconBLE]

/** @file
*
* @defgroup nrf_dev_radio_rx_example_main main.c
* @{
* @ingroup nrf_dev_radio_rx_example
* @brief Radio Receiver example Application main file.
*
* This file contains the source code for a sample application using the NRF_RADIO peripheral.
*
*/
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include "radio_config.h"
#include "nrf_gpio.h"
#include "boards.h"
#include "bsp.h"
#include "app_timer.h"
#include "nordic_common.h"
#include "nrf_error.h"
#include "app_error.h"
 #define NRF_LOG_MODULE_NAME "APP"
#include "nrf_log.h"
#include "nrf_log_ctrl.h"

#define APP_TIMER_PRESCALER      0                     /**< Value of the RTC1 PRESCALER register. */
#define APP_TIMER_OP_QUEUE_SIZE  2                     /**< Size of timer operation queues. */

static uint32_t                   packet;             /**< Packet to transmit. */


/**@brief Function for initialization oscillators.
 */
void clock_initialization()
{
    /* 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.
    }

    /* Start low frequency crystal oscillator for app_timer(used by bsp)*/
    NRF_CLOCK->LFCLKSRC            = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);
    NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
    NRF_CLOCK->TASKS_LFCLKSTART    = 1;

    while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
    {
        // Do nothing.
    }
}


/**@brief Function for reading packet.
 */
uint32_t read_packet()
{
    uint32_t result = 0;

    NRF_RADIO->EVENTS_READY = 0U;
    // Enable radio and wait for ready
    NRF_RADIO->TASKS_RXEN = 1U;

    while (NRF_RADIO->EVENTS_READY == 0U)
    {
        // wait
    }
    NRF_RADIO->EVENTS_END = 0U;
    // Start listening and wait for address received event
    NRF_RADIO->TASKS_START = 1U;

    // Wait for end of packet or buttons state changed
    while (NRF_RADIO->EVENTS_END == 0U)
    {
        // wait
    }

    if (NRF_RADIO->CRCSTATUS == 1U)
    {
        result = packet;
    }
    NRF_RADIO->EVENTS_DISABLED = 0U;
    // Disable radio
    NRF_RADIO->TASKS_DISABLE = 1U;

    while (NRF_RADIO->EVENTS_DISABLED == 0U)
    {
        // wait
    }
    return result;
}


/**
 * @brief Function for application main entry.
 * @return 0. int return type required by ANSI/ISO standard.
 */
int main(void)
{
	  
	
    uint32_t err_code = NRF_SUCCESS;

    clock_initialization();
    APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, NULL);

    err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);
    err_code = bsp_init(BSP_INIT_LED, APP_TIMER_TICKS(100, APP_TIMER_PRESCALER), NULL);
    APP_ERROR_CHECK(err_code);

    // Set radio configuration parameters
    radio_configure();
    NRF_RADIO->PACKETPTR = (uint32_t)&packet;

    err_code = bsp_indication_set(BSP_INDICATE_USER_STATE_OFF);
    NRF_LOG_INFO("Wait for first packet\r\n");
    APP_ERROR_CHECK(err_code);
    NRF_LOG_FLUSH();    

    while (true)
    {
        uint32_t received = read_packet();
				
				
        err_code = bsp_indication_set(BSP_INDICATE_RCV_OK);
				uint32_t rssi = NRF_RADIO->RSSISAMPLE; //changes
        NRF_LOG_INFO("Packet was received\r\n");
        APP_ERROR_CHECK(err_code);

        NRF_LOG_INFO("The contents of the package is %u\r\n", (unsigned int)received);
				NRF_LOG_INFO("The RSSI value is %u\r\n", (unsigned int)rssi); //changes
        NRF_LOG_FLUSH();
    }
}

Hello, Hope you are doing well. I made the changes in the code above in receiver. Only the lines with //changes have modified and I ran the transmitter and the receiver code. The problem I am facing is that in the serial port the RSSISAMPLE register is always showing me value 0. No matter the distance between the transmitter and receiver. I have attached a screenshot of the output. If you could tell me why I am getting the RSSI value as 0. It will be of great help.

Also, If you have an example for the nRF51Dk using interrupts that I could work with for my project, it will really help me a lot.

Thank You.