CC1120: Very big jitter in transparent mode

Not fully clear what you are doing:

- Could you share you register setting?

- Have you checked that the data on the air is correct?

- " I try to set different data rates, but only data rates low 125 kHz sets correct frequency on GPIO, all values higher set 125 kHz clock." Not sure which parameter you are changing and if you change it on the RX or TX side. Please elaborate.

My register setting:

  {CC1200_IOCFG2,            0x08},
  {CC1200_IOCFG0,            0x09},
  {CC1200_SYNC_CFG1,         0xAB},
  {CC1200_DEVIATION_M,       0xD1},
  {CC1200_MODCFG_DEV_E,      0x18},
  {CC1200_DCFILT_CFG,        0x5D},
  {CC1200_PREAMBLE_CFG1,     0x00},
  {CC1200_PREAMBLE_CFG0,     0x8A},
  {CC1200_IQIC,              0x4B},
  {CC1200_CHAN_BW,           0x01},
  {CC1200_MDMCFG1,           0x06},
  {CC1200_MDMCFG0,           0x41},
  {CC1200_SYMBOL_RATE2,      0xC9},
  {CC1200_SYMBOL_RATE1,      0x99},
  {CC1200_SYMBOL_RATE0,      0x9A},
  {CC1200_AGC_REF,           0x4E},
  {CC1200_AGC_CS_THR,        0xEC},
  {CC1200_AGC_CFG1,          0x51},
  {CC1200_AGC_CFG0,          0x87},
  {CC1200_FIFO_CFG,          0x00},
  {CC1200_FS_CFG,            0x12},
  {CC1200_PKT_CFG2,          0x03},
  {CC1200_PKT_CFG1,          0x00},
  {CC1200_PKT_CFG0,          0x20},
  {CC1200_PA_CFG1,           0x3F},
  {CC1200_PA_CFG0,           0x50},
  {CC1200_ASK_CFG,           0x3F},
  {CC1200_PKT_LEN,           0xFF},
  {CC1200_IF_MIX_CFG,        0x1C},
  {CC1200_FREQOFF_CFG,       0x22},
  {CC1200_MDMCFG2,           0x0C},
  {CC1200_FREQ2,             0x56},
  {CC1200_FREQ1,             0x73},
  {CC1200_FREQ0,             0x33},
  {CC1200_IF_ADC1,           0xEE},
  {CC1200_IF_ADC0,           0x10},
  {CC1200_FS_DIG1,           0x07},
  {CC1200_FS_DIG0,           0xAF},
  {CC1200_FS_CAL1,           0x40},
  {CC1200_FS_CAL0,           0x0E},
  {CC1200_FS_DIVTWO,         0x03},
  {CC1200_FS_DSM0,           0x33},
  {CC1200_FS_DVC0,           0x17},
  {CC1200_FS_PFD,            0x00},
  {CC1200_FS_PRE,            0x6E},
  {CC1200_FS_REG_DIV_CML,    0x1C},
  {CC1200_FS_SPARE,          0xAC},
  {CC1200_FS_VCO0,           0xB5},
  {CC1200_XOSC5,             0x0E},
  {CC1200_XOSC1,             0x03},
  {CC1200_SERIAL_STATUS,     0x08},

Data on the air have big jitter. I see by oscilloscope on transmit antenna.

I change bitrate on TX side (registers SYMBOL_RATE0-2). Then I set value below 125 ksps, it set correct, I see on GPIO2 (TX side) correct frequency, but if I set value higher 125 kbps, I see 125 kHz.

My problem is only on TX side. Data on RX side are the same as on TX antenna.

If you want to send 16 kbps, why do you adjust the SYMBOL_RATE to > 100 kbps?

I need to use radio for PLL, and I need low jitter and correct signal front positions.

Would you be able to share a blokc diagram or similar how you plan to use the C1120? I don't understand what you mean by "use radio for PLL", please elaborate. 

This is a block diagram of my system.

Transparent mode on CC1200 will generate jitter and we generally advice to oversample the received signal to ensure good enough RX performance. Due to the jitter, the receiver should not use edge detect.