CC1120 rssi

See e2e.ti.com/.../891913

hi,

I haven't solve this problem.

reg config is this:

  {CC112X_IOCFG3,            0xB0},
  {CC112X_IOCFG2,            0x06},
  {CC112X_IOCFG1,            0xB0},
  {CC112X_IOCFG0,            0x40},
  {CC112X_SYNC_CFG1,         0x08},
  {CC112X_DEVIATION_M,       0x48},
  {CC112X_MODCFG_DEV_E,      0x0D},
  {CC112X_DCFILT_CFG,        0x1C},
  {CC112X_IQIC,              0x00},
  {CC112X_CHAN_BW,           0x02},
  {CC112X_MDMCFG0,           0x05},
  {CC112X_DRATE2,      0x93},
  {CC112X_AGC_CS_THR,        0x19},
  {CC112X_AGC_CFG1,          0xA9},
  {CC112X_AGC_CFG0,          0xCF},
  {CC112X_FIFO_CFG,          0x00},
  {CC112X_FS_CFG,            0x14},
  {CC112X_PKT_CFG0,          0x20},
  {CC112X_PA_CFG0,           0x7B},
  {CC112X_PKT_LEN,           0xFF},
  {CC112X_IF_MIX_CFG,        0x00},
  {CC112X_FREQOFF_CFG,       0x22},
  {CC112X_FREQ2,             0x6C},
  {CC112X_FREQ1,             0x80},
  {CC112X_FS_DIG1,           0x00},
  {CC112X_FS_DIG0,           0x5F},
  {CC112X_FS_CAL1,           0x40},
  {CC112X_FS_CAL0,           0x0E},
  {CC112X_FS_DIVTWO,         0x03},
  {CC112X_FS_DSM0,           0x33},
  {CC112X_FS_DVC0,           0x17},
  {CC112X_FS_PFD,            0x50},
  {CC112X_FS_PRE,            0x6E},
  {CC112X_FS_REG_DIV_CML,    0x14},
  {CC112X_FS_SPARE,          0xAC},
  {CC112X_FS_VCO0,           0xB4},
  {CC112X_XOSC5,             0x0E},
  {CC112X_XOSC1,             0x03},

init:

unsigned char cc112xRssiOffset = 102;

  cc112xSpiWriteReg(CC112X_AGC_GAIN_ADJUST,&cc112xRssiOffset,1);

//this code is read RSSI from TI document

int 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;
}

// this code in the main loop

if (rxBytes != 0)                                     // Check that we have bytes in fifo
    {               
      cc112xSpiReadReg(CC112X_MARCSTATE, &marcStatus, 1);// Read marcstate to check for RX FIFO error,检测接收是否错误
              
      if ((marcStatus & 0x1F) == RX_FIFO_ERROR){          // Mask out marcstate bits and check if we have a RX FIFO error            
        
        trxSpiCmdStrobe(CC112X_SFRX);                    // Flush RX Fifo
      }
      else{                                              // Read n bytes from rx fifo，接收到有效的数据包
        cc112xSpiReadRxFifo(radio_to_buffer, rxBytes);
        
        if(radio_to_buffer[rxBytes-1] & 0x80)
        {                      
          //buffer_to_uart[0] = rxBytes;
          temp = rxBytes;
          rxBufferuartlength = temp - 4;
          for(i = 0; i < temp; i++)
          {
            buffer_to_uart[i] = radio_to_buffer[i];        //提取RADIO有效数据                     
          }
          // 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
          RSSI = Read8BitRssi();
          RSSI = ~RSSI+1; //read RSSI
          radio_to_buffer_flag = 1;                        //缓冲区有数据标志位，代表有 有效的RF数据接收到
          halLedSetRxled();                               //启动接收LED，串口发送完毕后关闭LED
        }
      }

but i found the value is wrang.

pls check what the problem in the code?

best regard

selina

- Could you please elaborate what you are measuring? What is "wrong value"?
- Why this line ?: RSSI = ~RSSI+1; //read RSSI

when i used this function: RSSI = Read8BitRssi();
debug with IAR,RSSI = 0XC6,it not a correct value.because it has a very Close distance,the modules are normally.
RSSI = ~RSSI+1; //read RSSI , this is Negative into positive.
so what i can do next?

0xC6, is this after you have converted to a positive value? Could you please provide a table before conversion to positive numbers in decimal? Note that for a system that uses IF the saturated RSSI value is -9 dBm.

hi,

when two module distance is 20cm,the rssiConverted = (int8)rssi2compl - rssiOffset; (rssiConverted = 0x39);

when two module distance is 10cm,the rssiConverted = (int8)rssi2compl - rssiOffset; (rssiConverted = 0x43);

when two module distance is 5cm,the rssiConverted = (int8)rssi2compl - rssiOffset; (rssiConverted = 0x49);

when two module distance is 5cm,the rssiConverted = (int8)rssi2compl - rssiOffset; (rssiConverted = 0x50);

 I had test this,the module no PA.

 the result is wrong,the RSSI all are positive value.

what wrong with this ?

best regard

selina

I pasted the Read8BitRssi(void) from your post directly into the easylink example and called RSSI = Read8BitRssi(); after reading the Rx buffer. I get correct negative values. Could be that you read the RSSI the wrong place in the code, try append status and see if you get the same results here.

Have you used this code in you project: cc112xSpiWriteReg(CC112X_AGC_GAIN_ADJUST,&cc112xRssiOffset,1);When i removed thie code,and make rssiOffset =70; I found the RSSI value maybe correct.could you stick your code on this post or send to my email,that i can check what's wrong with my project.

On the way, I don't find  this code cc112xSpiWriteReg(CC112X_AGC_GAIN_ADJUST,&cc112xRssiOffset,1)  in the swrc219c docment,so I remove it.

if you found ,please tell me.

thks.

best regards

selina

I have used AGC_GAIN_ADJUST=0.

How do you know if the RSSI is correct or not? Have you done conducted tests with known signal strength?

I ueed IAR debug，when I make two module very nearly,the RSSI is -9DBM,and the distance is farther,the RSSI is smaller, so I think it is correct.
could you try to test the AGC_GAIN_ADJUST=102 and tell me the result.
best regards
selina