Rssi Value In CC1120 Acknowledge Packet

Caner Dinçer

Prodigy 170 points

Hi all,

Can we read the rssi value in acknowledge packet ?It is possible?

Best

over 9 years ago

0 TER over 9 years ago

TI__Guru**** 317180 points

For all received packets it's possible to find from the RSSI registers what the RSSI was. On the PHY layer C1120 doesn't know that the packet is ACK or something else.

0 Caner Dinçer over 9 years ago in reply to TER

Prodigy 170 points

Hi Ter,

Firstly,thanks your answer. I'm getting the rssi value from acknowledge packet now but this value doesn't change that it seems as stable whenever the distance is increased between Receiver and Transmitter devices.

My code is as below;

cc112xSpiReadReg(CC112X_RSSI1,&rssi_readout,1);
rssi = (int16)((int8)rssi_readout) - RssiOffset;

At this point, i'm nearly getting the rss value as 32 ( I think that it is wrong value) in acknowledge packet from Transmitter device and getting the rss value as 237 in Receiver device. Why don't we see the rss values as equal? Do you have any idea about this problem?

Best

0 TER over 9 years ago in reply to Caner Dinçer

TI__Guru**** 317180 points

First of all the RSSI should be a negative value.

And yes, if the Tx and Rx side are equal the RSSI should be equal to (or within a dB or two)

Is this your own hardware? If so, send a packet from board A and use SmartRF Studio to receive it and check the RSSI value. Same with board B. If the value is the same, is the RSSI read the same both for the main packet and the ack packet? Is the timing the same?

0 Caner Dinçer over 9 years ago in reply to TER

Prodigy 170 points

Fullscreen tx_rssi.txt Download

void sendBeacon(void) {
 
   
    // Initialize packet buffer of size PKTLEN + 1
    uint8 txBuffer[PKTLEN+1] = {0};
    
    packetCounterTX = 0;

    
    tx_registers();    
    
    // Connect ISR function to GPIO2
    ioPinIntRegister(&radioRxTxISR);

    // Interrupt on falling edge
    ioPinIntTypeSet(IO_PIN_FALLING_EDGE);

    // Clear ISR flag
    ioPinIntClear();

    // Enable interrupt
    ioPinIntEnable();

    // Calibrate radio according to errata
    manualCalibration();
    
    //trxSpiCmdStrobe(CC112X_SAFC); automatic frequency compensation   
      //do {   
    
      
     while(1){
    
    // Wait for button push
      
      //Continiously sent packets until button is pressed
      do{
        
        // Update packet counter
        packetCounterTX++;
        
        // Create a random packet with PKTLEN + 2 byte packet counter + n x random bytes
        createPacket(txBuffer);
        
        // Write packet to tx fifo
        cc112xSpiWriteTxFifo(txBuffer,sizeof(txBuffer));
        
        // Strobe TX to send packet
        trxSpiCmdStrobe(CC112X_STX);
        
        // Wait for interrupt that packet has been sent. 
        // (Assumes the GPIO connected to the radioRxTxISR function is set 
        // to GPIOx_CFG = 0x06)
        while(!packetSemaphore) {
          uint8 readByte;
          //Read datarate from registers
          cc112xSpiReadReg(CC112X_MARCSTATE, &readByte, 1);
          if(readByte);
        };
        
        // Clear semaphore flag
        packetSemaphore = ISR_IDLE;

        rssi = Read8BitRssi();
              
        write_tx();
        
      }while(!SW_PUSH);
    
  }
  // Put radio to sleep and exit application
  //trxSpiCmdStrobe(CC112X_SPWD);  
}


uint8 Read8BitRssi(void){
 uint8 rssi2compl,rssiValid;
 uint8 rssiOffset = 102;
 int8 rssiConverted;
 //Read RSSI_VALID from RSSI0
 cc112xSpiReadReg(CC112X_RSSI0, &rssiValid, 1);
 // Check if the RSSI_VALID flag is set
 if(rssiValid & 0x01){
 // Read RSSI from MSB register
 cc112xSpiReadReg(CC112X_RSSI1, &rssi2compl, 1);
 rssiConverted = (int8)rssi2compl - rssiOffset;
 return rssiConverted;
 }
 // return 0 since new value is not valid
 return 0;
}

static void tx_registers(void) {
 
    uint8 writeByte;       

    registerConfig();
    //RX Gain
    writeByte = 0x04; cc112xSpiWriteReg(CC112X_CHAN_BW, &writeByte, 1);  // RX filter bandwidth 200kHz
    writeByte = 0x11; cc112xSpiWriteReg(CC112X_AGC_CFG3, &writeByte, 1); //adjust min gain 
    writeByte = 0x20; cc112xSpiWriteReg(CC112X_AGC_CFG2, &writeByte, 1); //0x20-->max gain 0xA0-->previous gain
    writeByte = 0x19; cc112xSpiWriteReg(CC112X_AGC_REF, &writeByte, 1);  //0x19
     
    //TX Power
    writeByte = 0x7F; cc112xSpiWriteReg(CC112X_PA_CFG2, &writeByte, 1);
    writeByte = 0x56; cc112xSpiWriteReg(CC112X_PA_CFG1, &writeByte, 1);
    writeByte = 0x7C; cc112xSpiWriteReg(CC112X_PA_CFG0, &writeByte, 1);
    
    // TXOFF_MODE = RX
    writeByte = 0x38; cc112xSpiWriteReg(CC112X_RFEND_CFG0, &writeByte, 1); 
    
    // RXOFF_MODE = RX
    writeByte = 0x3F; cc112xSpiWriteReg(CC112X_RFEND_CFG1, &writeByte, 1); 
    
    // Max packet length = 2
    writeByte = 0x02; cc112xSpiWriteReg(CC112X_PKT_LEN, &writeByte, 1);  //auto ack. paketi --> Length + Address of transmitter + Address of receiver     
      
}

Hi Ter,

Yes, the hardware is our own design. I have done some the change after your last reply in our Rx and TX function and which was checked at the SmartRF Studio.

Now, we are receiving decreasing rssi value when we increase the distance between RX and TX devices but we aren't receiving rssi value in acknowledge response in TX device. ( Maybe, there is a missing register )

I'm sharing the our TX codes as attached. Why didn't we receive rss value in TX device? Could you examine rssi part in this code?

Best

0 Caner Dinçer over 9 years ago in reply to Caner Dinçer

Prodigy 170 points

Hi Ter,

Do you have any suggestion about last reply ?

Best

0 TER over 9 years ago in reply to Caner Dinçer

TI__Guru**** 317180 points

Correct me if I'm wrong but it looks like you don't strobe Rx to listen for the ACK?

0 Caner Dinçer over 9 years ago in reply to TER

Prodigy 170 points

Fullscreen tx_rssi_20.10.2015.txt Download

void sendBeacon(void) {
 
   
    // Initialize packet buffer of size PKTLEN + 1
    uint8 txBuffer[PKTLEN+1] = {0};
    uint8 rxBuffer[10] ;
    uint8 control = 1;
    
    packetCounterTX = 0;
   
    
    while(control){
    
    tx_registers();    
    
    // Connect ISR function to GPIO2
    ioPinIntRegister(&radioRxTxISR);

    // Interrupt on falling edge
    ioPinIntTypeSet(IO_PIN_FALLING_EDGE);

    // Clear ISR flag
    ioPinIntClear();

    // Enable interrupt
    ioPinIntEnable();

    // Calibrate radio according to errata
    manualCalibration();
    
    //trxSpiCmdStrobe(CC112X_SAFC); automatic frequency compensation   
      //do {   
    
      
    
    
    // Wait for button push
      
      //Continiously sent packets until button is pressed
      do{
        
        // Update packet counter
        packetCounterTX++;
        
        // Create a random packet with PKTLEN + 2 byte packet counter + n x random bytes
        createBeacon(txBuffer);
        
        // Write packet to tx fifo
        cc112xSpiWriteTxFifo(txBuffer,sizeof(txBuffer));
        
        // Strobe TX to send packet
        trxSpiCmdStrobe(CC112X_STX);
        
        // Wait for interrupt that packet has been sent. 
        // (Assumes the GPIO connected to the radioRxTxISR function is set 
        // to GPIOx_CFG = 0x06)
        while(!packetSemaphore) {
          uint8 readByte;
          //Read datarate from registers
          cc112xSpiReadReg(CC112X_MARCSTATE, &readByte, 1);
          if(readByte);
        };
        
        // Clear semaphore flag
         
       
        
        trxSpiCmdStrobe(CC112X_SRX);
             
        Delay10msx(9);
         
        cc112xSpiReadRxFifo(rxBuffer, 8);     
     
        if( rxBuffer[2] == 0xBB)
            
             {          
           
            rssi = Read8BitRssi();
            TEST_LED = 1;      
            write_rx();
            control = 0;

             } 
        packetSemaphore = ISR_IDLE;
            
        
      }while(!SW_PUSH);
    
  }
  // Put radio to sleep and exit application
  //trxSpiCmdStrobe(CC112X_SPWD);  
}


void waitBeacon(void) {
    
  
    uint8 rxBuffer[128] = {0};
    uint8 rxBytes;
    uint8 txTest[3];
    uint8 control = 1;
    uint8 marcStatus;
    packetCounterRX = 0;
    control = 1;
    
    //The Ack. packet should be written to the TX FIFO before RX mode is being entered
    
    rx_registers();
    
    txTest[0] = 2;            // Length
    txTest[1] = 0xAA;         // Transmitter address
    txTest[2] = 0xBB;         // Adres onay�
    
    
    // Connect ISR function to GPIO2
    ioPinIntRegister(&radioRxTxISR);  //P4.4 GPIO2 

    // Interrupt on falling edge
    ioPinIntTypeSet(IO_PIN_FALLING_EDGE);

    // Clear ISR flag
    ioPinIntClear();

    // Enable interrupt
    ioPinIntEnable();
       
    manualCalibration();   //her seferinde gerek var m�? test edilmeli.
    
    
    cc112xSpiWriteTxFifo(txTest, sizeof(txTest));

                
    // Set radio in RX      
    trxSpiCmdStrobe(CC112X_SRX); 
    
   
       
    while(control){
         
      
    
    // Wait for packet received interrupt 
    if(packetSemaphore == ISR_ACTION_REQUIRED){
      
      // Read number of bytes in rx fifo
      cc112xSpiReadReg(CC112X_NUM_RXBYTES, &rxBytes, 1);
      
      // Check that we have bytes in fifo
      if(rxBytes != 0){
        
        // Read marcstate to check for RX FIFO error
        cc112xSpiReadReg(CC112X_MARCSTATE, &marcStatus, 1);
        
        // Mask out marcstate bits and check if we have a RX FIFO error
        if((marcStatus & 0x1F) == RX_FIFO_ERROR){
          
          // Flush RX Fifo
          trxSpiCmdStrobe(CC112X_SFRX);
        }
        else{
        
          // Read n bytes from rx fifo
          cc112xSpiReadRxFifo(rxBuffer, rxBytes);  
          
          // Check CRC ok (CRC_OK: bit7 in second status byte)
          // This assumes status bytes are appended in RX_FIFO
          // (PKT_CFG1.APPEND_STATUS = 1.)
          // If CRC is disabled the CRC_OK field will read 1
          if(rxBuffer[rxBytes-1] & 0x80){
            
            // Update packet counter
            packetCounterRX++;
            
            for(uint8 i=0; i<rxBytes; i++)
            receivedData[i] = rxBuffer[i]; 
            
          }
        }
      }
      
      // Update LCD
      //updateLcd();
      
      
            if(receivedData[2] == 'N'){
              
              packetSemaphore = 0;
              
              rssi = Read8BitRssi();
              
              write_rx();
              
              
              // Write packet to tx fifo
              cc112xSpiWriteTxFifo(txTest, sizeof(txTest));
              
              // Strobe TX to send packet
              trxSpiCmdStrobe(CC112X_STX);
              
              Delay10msx(9);
              
              // Wait for interrupt that packet has been sent. 
              // (Assumes the GPIO connected to the radioRxTxISR function is set 
              // to GPIOx_CFG = 0x06)
              while(!packetSemaphore) {
                uint8 readByte;
                //Read datarate from registers
                cc112xSpiReadReg(CC112X_MARCSTATE, &readByte, 1);
                if(readByte);
              };
              
              // Reset packet semaphore
              packetSemaphore = ISR_IDLE;
              
              control = 0;
              
              //sendDeviceAddress();
              //Flag2.BeaconWasTaken = 1;
              //control = 0;
                       
      
      }
      
  
      
      // Set radio back in RX
      // trxSpiCmdStrobe(CC112X_SRX);
      
      
    trxSpiCmdStrobe(CC112X_SFRX);

    Delay10msx(10);
    
    trxSpiCmdStrobe(CC112X_SFTX);

    Delay10msx(10);

    trxSpiCmdStrobe(CC112X_SRES);
      
    }
  } 
  // Put radio to sleep and exit application
  //trxSpiCmdStrobe(CC112X_SPWD);
}


static void rx_registers(void) {
  
    uint8 writeByte;     
    
    registerConfig();
    
    //RX Gain
    writeByte = 0x04; cc112xSpiWriteReg(CC112X_CHAN_BW, &writeByte, 1); //RX filter bandwidth 200kHz
    writeByte = 0x11; cc112xSpiWriteReg(CC112X_AGC_CFG3, &writeByte, 1); //adjust min gain 
    writeByte = 0x20; cc112xSpiWriteReg(CC112X_AGC_CFG2, &writeByte, 1); //0x20-->max gain 0xA0-->previous gain
    writeByte = 0x19; cc112xSpiWriteReg(CC112X_AGC_REF, &writeByte, 1);  //0x19
    
    //TX Power
    writeByte = 0x7F; cc112xSpiWriteReg(CC112X_PA_CFG2, &writeByte, 1);
    writeByte = 0x56; cc112xSpiWriteReg(CC112X_PA_CFG1, &writeByte, 1);
    writeByte = 0x7C; cc112xSpiWriteReg(CC112X_PA_CFG0, &writeByte, 1);
      
    // LBT
    writeByte = 0x10; cc112xSpiWriteReg(CC112X_PKT_CFG2, &writeByte, 1); //Indicates clear channel when RSSI is below threshold and ETSI LBT requirements are met
    writeByte = 10; cc112xSpiWriteReg(CC112X_AGC_CS_THR, &writeByte, 1); //carrier sense threshold = CS threshold - RSSI offset = -92 - (-102) = 10
    
    // TXOFF_MODE = RX
    writeByte = 0x38; cc112xSpiWriteReg(CC112X_RFEND_CFG0, &writeByte, 1); 
    
    //RX Off mode=TX
    writeByte = 0x2E; cc112xSpiWriteReg(CC112X_RFEND_CFG1, &writeByte, 1);
    
}

/*******************************************************************************
*   @fn         tx_registers
*
*   @brief      Transmitter'a �zel register ayarlar�. Ref: 1120 User Guide
*
*   @param      none
*
*   @return     none
*/
static void tx_registers(void) {
 
    uint8 writeByte;       

    registerConfig();
    //RX Gain
    writeByte = 0x04; cc112xSpiWriteReg(CC112X_CHAN_BW, &writeByte, 1);  // RX filter bandwidth 200kHz
    writeByte = 0x11; cc112xSpiWriteReg(CC112X_AGC_CFG3, &writeByte, 1); //adjust min gain 
    writeByte = 0x20; cc112xSpiWriteReg(CC112X_AGC_CFG2, &writeByte, 1); //0x20-->max gain 0xA0-->previous gain
    writeByte = 0x19; cc112xSpiWriteReg(CC112X_AGC_REF, &writeByte, 1);  //0x19
     
    //TX Power
    writeByte = 0x7F; cc112xSpiWriteReg(CC112X_PA_CFG2, &writeByte, 1);
    writeByte = 0x56; cc112xSpiWriteReg(CC112X_PA_CFG1, &writeByte, 1);
    writeByte = 0x7C; cc112xSpiWriteReg(CC112X_PA_CFG0, &writeByte, 1);
    
    // TXOFF_MODE = RX
    writeByte = 0x38; cc112xSpiWriteReg(CC112X_RFEND_CFG0, &writeByte, 1); 
    
    // RXOFF_MODE = RX
    writeByte = 0x3F; cc112xSpiWriteReg(CC112X_RFEND_CFG1, &writeByte, 1); 
    
    // Max packet length = 2
    writeByte = 0x02; cc112xSpiWriteReg(CC112X_PKT_LEN, &writeByte, 1);  //auto ack. paketi --> Length + Address of transmitter + Address of receiver     
      
}

uint8 Read8BitRssi(void){
 uint8 rssi2compl,rssiValid;
 uint8 rssiOffset = 102;
 int8 rssiConverted;
 //Read RSSI_VALID from RSSI0
 cc112xSpiReadReg(CC112X_RSSI0, &rssiValid, 1);
 // Check if the RSSI_VALID flag is set
 if(rssiValid & 0x01){
 // Read RSSI from MSB register
 cc112xSpiReadReg(CC112X_RSSI1, &rssi2compl, 1);
 rssiConverted = (int8)rssi2compl - rssiOffset;
 return rssiConverted;
 }
 // return 0 since new value is not valid
 return 0;
}

Hi Ter,

Great, i have added the strobe as you say in attached and we are getting rss value in acknowledge packet but it look like there is a problem.

Normally, we are getting 200 rss value nearly at the RX device but who are getting 136 rss value at the TX device(ack packet).

We are receiving decreasing rssi value for RX device when we increase the distance between RX and TX devices but acknowledge rss value doesn't change when increase the distance.

Maybe, the pulse interval of acknowledge packet is less than normal TX. Do you have any idea about why doesn't change the value of this rss?

Best

0 TER over 9 years ago in reply to Caner Dinçer

TI__Guru**** 317180 points

Do you know if you have actually received the ack packet? Receiving a ack packet is equal to receiving a normal packet. It could be that you read the last RSSI value or similar since it's not changing.

Sub-1 GHz

Sub-1 GHz forum

Rssi Value In CC1120 Acknowledge Packet