how to test RSSI use code

Why do you say that SmartRF Studio is too much trouble?

The function RF_getRssi() always returns the most up-to-date RSSI value. It basically issues a CMD_GET_RSSI (refer to the [TRM| ] p. 1506) and returns the content of the RSSIVAL register from the RF core. When calling RF_getRssi(), please be aware of the these conditions:

- The RF core has to be in RX mode. Otherwise, -128 (invalid RSSI) is returned.

- How often, how fast and when exactly RSSIVAL is updated, depends highly on the current command.

- After issuing the first RX command, RF_getRssi() may return 0 for a very short time (some microseconds) and the returned value might not be stable immediately. A delay of 1ms should get you on the safe side. We are currently investigating, how we can guarantee that RF_getRssi() always returns the next available valid RSSI value. I also admit, that we need to improve the API documentation.

The RSSI of the last received packet is only available in the packet itself.

Here is a code snippet that shows how to measure the RSSI with a RX Test command. Any other RX command would work as well.

    int8_t rssi = (int8_t)RF_GET_RSSI_ERROR_VAL; 

    // CMD_RX_TEST 
    volatile rfc_CMD_RX_TEST_t RF_cmdRxTest = 
    { 
                    .commandNo = CMD_RX_TEST, 
                    .status = 0x0000, 
                    .pNextOp = 0, // INSERT APPLICABLE POINTER: (uint8_t*)&xxx 
                    .startTime = 0x00000000, 
                    .startTrigger.triggerType = TRIG_NOW, 
                    .startTrigger.bEnaCmd = 0x0, 
                    .startTrigger.triggerNo = 0x0, 
                    .startTrigger.pastTrig = 0x0, 
                    .condition.rule = COND_NEVER, 
                    .condition.nSkip = 0x0, 
                    .config.bEnaFifo = 0x0, 
                    .config.bFsOff = 0x1, 
                    .config.bNoSync = 0x1, 
                    .endTrigger.triggerType = TRIG_REL_START, 
                    .endTrigger.bEnaCmd = 0x0, 
                    .endTrigger.triggerNo = 0x0, 
                    .endTrigger.pastTrig = 0x0, 
                    .syncWord = 0x930b51de, 
                    .endTime = EasyLink_ms_To_RadioTime(10), 
    }; 

    // Execute the command asynchronously 
    RF_CmdHandle cmd = RF_postCmd(rfHandle, (RF_Op*)&RF_cmdRxTest, 
            RF_PriorityNormal, 0, EASYLINK_RF_EVENT_MASK); 

    // Make sure that the RX_TEST command is running 
    while (RF_cmdRxTest.status != ACTIVE); 

    // Even though the command is running, we have to wait for the RF core to be in receive mode 
    // Otherwise it returns 0 
    while ((rssi == RF_GET_RSSI_ERROR_VAL) || (rssi == 0)) 
    { 
        rssi = RF_getRssi(rfHandle); 
    } 

hi TER：

Thanks for your reply.

I have a question:Why you add "while ((rssi == RF_GET_RSSI_ERROR_VAL) || (rssi == 0))" before reading RSSI Value?

I tried like what you said,it returned at the first time ,and then it returned nothing.

hi Richard

Thanks for your reply.

I mean RSSI returned at the first time because rssi value was initialled by RF_GET_RSSI_ERROR_VAL, and then rssi value was read by rssi = RF_getRssi(rfHandle); now rssi value neither equals to RF_GET_RSSI_ERROR_VAL nor 0,so it never enters while ((rssi == RF_GET_RSSI_ERROR_VAL) || (rssi == 0)).

Below is my test code,can you pls check if there is any problem?

    /* Request access to the radio */
    rfHandle = RF_open(&rfObject, &RF_prop, (RF_RadioSetup*)&RF_cmdPropRadioDivSetup, &rfParams);
    //rfHandle = RF_open(&rfObject, &RF_prop_lrm, (RF_RadioSetup*)&RF_cmdPropRadioDivSetup_lrm, &rfParams);

    /* Set the frequency */
    RF_runCmd(rfHandle, (RF_Op*)&RF_cmdFs, RF_PriorityNormal, NULL, 0);

    /* Enter RX mode and stay forever in RX */
    rxCmdHndl =  RF_postCmd(rfHandle, (RF_Op*)&RF_cmdPropRx, RF_PriorityNormal, &callback, IRQ_RX_ENTRY_DONE);

    while(1)
    {
      if(packetReceived)
      {
        packetReceived = 0;
        UART_write(uart, "Received OK!", 12);
      }
     
      while ((rssi == RF_GET_RSSI_ERROR_VAL) || (rssi == 0))
      {
        rssi = RF_getRssi(rfHandle);
        char string1[10];
        sprintf(string1,"Rssi Value:%ddB\r\n", rssi);
        UART_write(uart, string1, strlen(string1));
      }

void callback(RF_Handle h, RF_CmdHandle ch, RF_EventMask e)
{
    if (e & RF_EventRxEntryDone)
    {  
        packetReceived =1;
     
        /* Toggle pin to indicate RX */
        PIN_setOutputValue(pinHandle, Board_LED2,!PIN_getOutputValue(Board_LED2));

        /* Get current unhandled data entry */
        currentDataEntry = RFQueue_getDataEntry();

        /* Handle the packet data, located at &currentDataEntry->data:
         * - Length is the first byte with the current configuration
         * - Data starts from the second byte */
        packetLength      = *(uint8_t*)(&currentDataEntry->data);
        packetDataPointer = (uint8_t*)(&currentDataEntry->data + 1);

        /* Copy the payload + the status byte to the packet variable */
        memcpy(packet, packetDataPointer, (packetLength + 2));

        RFQueue_nextEntry();
    }
}

And this is test result:

No valid RSSI value is printed when RF received data.

Sorry, there was a misunderstanding. This loop is a delay loop that waits for a valid RSSI:

int rssi = RF_GET_RSSI_ERROR_VAL;
while ((rssi == RF_GET_RSSI_ERROR_VAL) || (rssi == 0))
{
    rssi = RF_getRssi(rfHandle);
}

Depending on the command timing it might run only once. After that you can do

while (1) 
{ 
    rssi = RF_getRssi(rfHandle); 
    char string1[10];
    sprintf(string1,"Rssi Value:%ddB\r\n", rssi);
    UART_write(uart, string1, strlen(string1));
}

hi richard

Thanks for your reply.

As you suggested,I modified my code like this:

    while ((rssi == RF_GET_RSSI_ERROR_VAL) || (rssi == 0))
      {
        rssi = RF_getRssi(rfHandle);
      }
   
    while(1)
    {
      if(packetReceived)
      {
        packetReceived = 0;
        UART_write(uart, "Received OK!\r\n", 14);

        char string1[30];
        rssi = RF_getRssi(rfHandle);
        sprintf(string1,"Rssi Value:%ddB\r\n", rssi);
        UART_write(uart, string1, strlen(string1));
      }
    }

When packet received correctly(packetreceived is set in RX Callback), print "Received OK" and the current RSSI Value, but the result is below:

Received OK!

Rssi Value:-99dB

Received OK!

Rssi Value:-101dB

Received OK!

Rssi Value:-104dB

Received OK!

Rssi Value:-94dB

Received OK!

Rssi Value:-95dB

Received OK!

Rssi Value:-101dB

Received OK!

Rssi Value:-100dB

Received OK!

Rssi Value:-100dB

Received OK!

It's very strange that the RSSI Value is very low, and if I modified my code if(packetReceived) to if(1), then correct RSSI value can be printed occasionally,like this:

Rssi Value:-99dB

Received OK!

Rssi Value:-101dB

Received OK!

Rssi Value:-104dB

Received OK!

Rssi Value:-14dB

Received OK!

Rssi Value:-95dB

Received OK!

Rssi Value:-101dB

Received OK!

Rssi Value:-100dB

Why is this strange? As long as you don't send anything on that frequency, -100dBm is totally valid. In the moment when you receive a packet, you can observe a RSSI of -14dBm when transceiver and receiver are close together.

If you are interested only in the RSSI of the received packet, then there is a more reliable way:

// Output structure for CMD_PROP_RX
rfc_propRxOutput_t rxStatistics;

// Set up RX command to output statistics data
RF_cmdPropRx.pOutput = (uint8_t*)&rxStatistics;

// Read RSSI after a packet has been received
int8 rssi = &rxStatistics.lastRssi;

does this code is fully functionnal and complete ? It can be reuse as it ? I am also looking at collecting RSSI