[Discuss-gnuradio] return value of function read_io()

[Fabian Uehlin]

Hello!

I try to build GNURadio with OpenBTS on a Ubuntu Linux system. I have  
the current revision of the repository running (10393).
GNURadio was built successfully and works, but OpenBTS didn't work,  
because RX failed to tune.

Following errors occur:
TRXManager.cpp:
WARNING -- RXTUNE failed with status 1
POWERON -- failed with status 1
Transceiver.cpp:
RX failed to tune

I ask my question in the GNURadio discussion list, because the problem  
is related to the USRP and his registers.

I have the source code (see below) and the function "rx_setFreq" which  
is called with the parameter freq = 1716400000,000000 (is calculated  
with 1724,4MHz: 1724400000.000000 -2*4000000 = wFreq-2*LO_OFFSET)
And then the function "compute_regs" is called. This function seems to  
be similar to usrp2/firmware/lib/db_rfx.c - "bool rfx_set_freq".

My problem is this line in the OpenBTS source code:
        if (m_uRx->read_io(1) & PLL_LOCK_DETECT)  return true;

m_uRx->read_io(1) = 0xff3b   = 1111 1111 0011 1011
PLL_LOCK_DETECT = 0x4   = 0000 0000 0000 0100
so the if condition is false it doesn't return true, but it should  
return true.

So I test several frequencies for looking after the value of m_uRx- 
>read_io(1):

-> GSM 1800 frequency			-> m_uRx->read_io(1) = 0xff3b -> does not  
tune, because Bit 2 is 0
-> GSM 850 and 900 frequencies	-> m_uRx->read_io(1) = 0xff3f -> does  
tune, because Bit 2 is 1 (but I don't have RFX900 daughterboards)

My questions: What does the function read_io(1) return? The values  
written to the fpga with function "_write_spi" N, R and control aren't
the values returned by read_io()?!

In my example with ARFCN 583 (1724,4MHz & 1819,4MHz) The values of R,  
N, control are:
Function rx_setFreq, (R & ~0x3) =                   0x340040
Function rx_setFreq, (R & ~0x3) | 1 =               0x340041
Function rx_setFreq, (control & ~0x3) =             0x4fc924
Function rx_setFreq, (control & ~0x3) | 0 = 0x4fc924
Function rx_setFreq, (N & ~0x3) =                   0x403528
Function rx_setFreq, (N & ~0x3) | 2 =               0x40352a

How does it calculate and return 0xff3b? And why does it only for  
GSM850/GSM900 return 0xff3f and not for GSM1800 (0xff3b)?

Thanks & Regards
        -Fabian-

-----

Source code of openbts/Transceiver/USRPDevice.cpp:

bool USRPDevice::rx_setFreq(double freq, double *actual_freq)
{
  unsigned R, control, N;
  printf("Function rx_setFreq, freq=%lf\n", freq);
  if (!compute_regs(freq, &R, &control, &N, actual_freq)) return false;
  printf("Function rx_setFreq, R=%x\n", R);
  printf("Function rx_setFreq, control=%x\n", control);
  printf("Function rx_setFreq, N=%x\n", N);
  if (R==0) return false;
  // static const unsigned SPI_FMT_MSB = (0 << 7);
  // static const unsigned SPI_ENABLE_RX_B = 0x80;
  // static const unsigned SPI_FMT_HDR_0 = (0 << 5);

  printf("Function rx_setFreq, SPI_ENABLE_RX_B=%x\n", SPI_ENABLE_RX_B);
  printf("Function rx_setFreq, SPI_FMT_MSB | SPI_FMT_HDR_0=%x\n",  
SPI_FMT_MSB | SPI_FMT_HDR_0);
  printf("Function rx_setFreq, (R & ~0x3)=%x\n", (R & ~0x3));
  printf("Function rx_setFreq, (R & ~0x3) | 1=%x\n", (R & ~0x3) | 1);

  m_uRx->_write_spi(0,SPI_ENABLE_RX_B,SPI_FMT_MSB | SPI_FMT_HDR_0,
                    write_it((R & ~0x3) | 1));
  printf("Function rx_setFreq, (control & ~0x3)=%x\n", (control &  
~0x3));
  printf("Function rx_setFreq, (control & ~0x3) | 0=%x\n", (control &  
~0x3) | 0);
  m_uRx->_write_spi(0,SPI_ENABLE_RX_B,SPI_FMT_MSB | SPI_FMT_HDR_0,
                    write_it((control & ~0x3) | 0));
  usleep(10000);
  printf("Function rx_setFreq, (N & ~0x3)=%x\n", (N & ~0x3));
  printf("Function rx_setFreq, (N & ~0x3) | 2=%x\n", (N & ~0x3) | 2);
  m_uRx->_write_spi(0,SPI_ENABLE_RX_B,SPI_FMT_MSB | SPI_FMT_HDR_0,
                    write_it((N & ~0x3) | 2));
  printf("Function rx_setFreq, m_uRx->read_io(1)=%x\n", m_uRx- 
>read_io(1));
  printf("Function rx_setFreq, PLL_LOCK_DETECT=%x\n", PLL_LOCK_DETECT);
  if (m_uRx->read_io(1) & PLL_LOCK_DETECT)  return true;
  if (m_uRx->read_io(1) & PLL_LOCK_DETECT)  return true;

  return false;
}

--------------------------------------------------------------------------------------------------------------------------------------------

Source code of openbts/Transceiver/USRPDevice.cpp:

const float USRPDevice::LO_OFFSET = 4.0e6;

bool USRPDevice::compute_regs(double freq,
                              unsigned *R,
                              unsigned *control,
                              unsigned *N,
                              double *actual_freq)
{

  float phdet_freq = 64.0e6/R_DIV;
  int desired_n = (int) round(freq*freq_mult/phdet_freq);
  *actual_freq = desired_n * phdet_freq/freq_mult;
  float B = floor(desired_n/16);
  float A = desired_n - 16*B;
  unsigned B_DIV = int(B);
  unsigned A_DIV = int(A);

  printf("Function compute_regs, freq=%lf\n", freq);
  printf("Function compute_regs, freq_mult=%i\n", freq_mult);
  printf("Function compute_regs, R_DIV=%i\n", R_DIV);
  printf("Function compute_regs, phdet_freq=%lf\n", phdet_freq);
  printf("Function compute_regs, desired_n=%i\n", desired_n);
  printf("Function compute_regs, actual_freq=%lf\n", actual_freq);
  printf("Function compute_regs, B=%lf\n", B);
  printf("Function compute_regs, A=%lf\n", A);
  printf("Function compute_regs, B_DIV=%i\n", B_DIV);
  printf("Function compute_regs, A_DIV=%i\n", A_DIV);

  if (B < A) return false;
  *R = (R_RSV<<22) |
    (BSC << 20) |
    (TEST << 19) |
    (LDP << 18) |
    (ABP << 16) |
    (R_DIV << 2);
  *control = (P<<22) |
    (PD<<20) |
    (CP2 << 17) |
    (CP1 << 14) |
    (PL << 12) |
    (MTLD << 11) |
    (CPG << 10) |
    (CP3S << 9) |
    (PDP << 8) |
    (MUXOUT << 5) |
    (CR << 4) |
    (PC << 2);
  *N = (DIVSEL<<23) |
    (DIV2<<22) |
    (CPGAIN<<21) |
    (B_DIV<<8) |
    (N_RSV<<7) |
    (A_DIV<<2);
  return true;
}