CC2520

Hi Bruno

I have had a quick look at your design and found no obvious explanation to a 16dB performance drop. Review in pdf is difficult, gerber files would provide a better base for checking the design, a schematic also is helpful.

The register settings seem Ok. One comment TXCTRL=0x94 is only intended for high temperature operation, else it should be 0x91

Suggest start checking component values, solder joints and  supply voltage on al VDD pins to debug the design. Sometimes current measurements also provide clues to what is happening. 

Tor-Inge

HI Tor-Inge,

I can now verify that the board is fine. It is something with the procedure for going  to TX mode.

When I put a break point in my code, after performing command strobe for calibration (INS_STXCAL) and wait roughly for 10 seconds, I get full power (3dBm) on the spectrum analyzer. It seems like the radio is not in transmit mode if I don't delay long enough even though the current is 34mA. So I guess that my procedure for getting in the TX mode is not correct. Can you please advice me what is the right procedure for going in TX mode after resetting the CC2520? I include the register setting and the part of the main:

Register settings:

TXCTRL->0x94

TXPOWER ->0xF7 //5dBm

MDMTEST0 ->0x65

MDMCTRL0 ->0x44

FRMCTRL0 -> 0x43

FRMCTRL1 ->0x00

EXTCLOCK -> 0x00

Part from Main:

Reset ;  // resetting the CC2520 AS per example code

Command_strobe(CC2520_INS_SXOSCON ); //Oscilator ON

__delay_cycles (500); // I run at default frequency through the DCODIV

Command_strobe(CC2520_INS_SNOP);
  __delay_cycles(500);
 Command_strobe(CC2520_INS_STXCAL);
__delay_cycles (500)   // I put the break point here and wait for roughly 10 sec and then hit play and I am getting the full power. If I don't wait the attenuation is 16dB.

Command_strobe(CC2520_INS_TXON);  // The current is correct I = 33mA
x = Command_strobe(CC2520_INS_SNOP );  //Check of the status byte.

while(1);

To summarise:

If I do not breakpoint on delay after TXCAL strobe I get 34mA and only -11dBm output, if I delay for 10 seconds I get 3dBm as expected.

Hi Bruno

This is a bit outside what I am familiar with. Hopefully, someone with low level programming skills can comment on this.

However, it is my understanding that there are two approaches to this. First, strobe STX and transceiver will calibrate and automatically start transmission of TXFIFO content after calibration. Second strategy is to monitor FSMSTAT0.CAL_RUNNING for a negative edge indicating finished calibration.

Tor-Inge

Hello Jani,

I found solution to my problem by building my own state machine for each of the modes (TX,RX,IDLE,LPM1,LPM2). So, if I want to go from LPM1 to TX I execute one piece of code if I want to go from RX to TX another piece of code etc. I was following the flow diagram on page 85 in the datasheet.  Here is a code example :

First reset the CC2520 with using RESETn, then initialize (registers) and then I call this function set_radio_mode  and put the radio in IDLE .

status = set_radio_mode(Radio_IDLE);//Go in IDLE
   
    Command_strobe(CC2520_INS_SFLUSHRX); //  Flush RXFIFO
    Command_strobe(CC2520_INS_SFLUSHTX); //  Flush TXFIFO
   CC2520_TXBUF(mpduLength,txMpdu); //Write to the TXFIFO
    status = set_radio_mode(Radio_TX);//Go in TX
  

unsigned char set_radio_mode ( unsigned char mode)

{

    case Radio_TX:
    {
       if (Prev_Radio_Mode==Radio_LPM1) //if the previous radio mode was LPM1 I do the following sequence of commands
       {
            Command_strobe(CC2520_INS_SXOSCON );
            Command_strobe(CC2520_INS_SNOP);
            P3OUT&=~1; //CS
                while (!(P3IN&BIT2));// wait until SO<>1
            P3OUT|=1;  
            while(!(Command_strobe(CC2520_INS_SNOP)&0x80));
            
           // now oscillator is stable and running
           
          Command_strobe(CC2520_INS_STXON);
          
         status = Command_strobe(CC2520_INS_SNOP);  
        }
        else //if (Prev_Radio_Mode==Radio_RX)
        {
           Command_strobe(CC2520_INS_STXON);
           status=Command_strobe(CC2520_INS_SNOP);      
       }
    
     Prev_Radio_Mode=Radio_TX;
    }
    break;
 
    case Radio_IDLE:
    {
        if (Prev_Radio_Mode==Radio_LPM1)
        {
            Command_strobe(CC2520_INS_SXOSCON);
          
            while(!(Command_strobe(CC2520_INS_SNOP)&0x80));
            Command_strobe(CC2520_INS_SRFOFF);
            status=Command_strobe(CC2520_INS_SNOP);
        }
        Prev_Radio_Mode=Radio_IDLE;
    }
    break;
    case Radio_LPM1:
    {
        Command_strobe(CC2520_INS_SRFOFF);
        Command_strobe(CC2520_INS_SXOSCOFF );
        Prev_Radio_Mode=Radio_LPM1;
    }
    break;
  }

}

Good luck,

Bruno.