Hello,
I have two PCBs each with a CC1120RHBR; one acts as a transmitter, the other acts as a receiver on 915 MHz. Both designs are identical as far as the schematic, layout, etc., which was copied directly from the TI Reference Design for 915 MHz. Several hundred of these boards have been built in the past, with a range of several hundred feet (which is more than acceptable).
However, on the current batch, I have 50 pairs, none of which will work more than 20 feet away from each other.
Here are my SmartRF init values:
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{ 0x0000, 0xB0 }, // IOCFG3 GPIO3 IO Pin Configuration
{ 0x0001, 0xB0 }, // IOCFG2 GPIO2 IO Pin Configuration
{ 0x0002, 0xB0 }, // IOCFG1 GPIO1 IO Pin Configuration
{ 0x0003, 0x06 }, // IOCFG0 GPIO0 IO Pin Configuration
{ 0x0004, 0xD3 }, // SYNC3 Sync Word Configuration [31:24]
{ 0x0005, 0x91 }, // SYNC2 Sync Word Configuration [23:16]
{ 0x0006, 0xD3 }, // SYNC1 Sync Word Configuration [15:8]
{ 0x0007, 0x91 }, // SYNC0 Sync Word Configuration [7:0]
{ 0x0008, 0x0B }, // SYNC_CFG1 Sync Word Detection Configuration
{ 0x000C, 0x1C }, // DCFILT_CFG Digital DC Removal Configuration
{ 0x000D, 0x18 }, // PREAMBLE_CFG1 Preamble Length Configuration
{ 0x0010, 0xC6 }, // IQIC Digital Image Channel Compensation Configuration
//{ 0x0011, 0x08 }, // CHAN_BW Channel Filter Configuration - 25kHz, w/ fosc = 32MHz
{ 0x0011, 0x02 }, // CHAN_BW Channel Filter Configuration - 100kHz, w/ fosc = 32MHz
{ 0x0013, 0x05 }, // MDMCFG0 General Modem Parameter Configuration
{ 0x0017, 0x20 }, // AGC_REF AGC Reference Level Configuration
{ 0x0018, 0x19 }, // AGC_CS_THR Carrier Sense Threshold Configuration
{ 0x001C, 0xA9 }, // AGC_CFG1 AGC Configuration
{ 0x001D, 0xCF }, // AGC_CFG0 AGC Configuration
{ 0x001E, 0x00 }, // FIFO_CFG FIFO Configuration
{ 0x0020, 0x03 }, // SETTLING_CFG Frequency Synthesizer Calibration and Settling Configuration
{ 0x0021, 0x12 }, // FS_CFG Frequency Synthesizer Configuration
{ 0x0026, 0x00 }, // PKT_CFG2 Packet Configuration, Reg 2
{ 0x0028, 0x20 }, // PKT_CFG0 Packet Configuration, Reg 0
{ 0x002E, 0x13 }, // PKT_LEN Packet Length Configuration
{ 0x2F00, 0x00 }, // IF_MIX_CFG IF Mix Configuration
{ 0x2F01, 0x22 }, // FREQOFF_CFG Frequency Offset Correction Configuration
//{ 0x2F05, 0x01 }, // CFM_DATA_CFG 0x01 for a CW transmission
{ 0x2F0C, 0x72 }, // FREQ2 Frequency Configuration [23:16]
{ 0x2F0D, 0x60 }, // FREQ1 Frequency Configuration [15:8]
{ 0x2F12, 0x00 }, // FS_DIG1
{ 0x2F13, 0x5F }, // FS_DIG0
{ 0x2F16, 0x40 }, // FS_CAL1
{ 0x2F17, 0x0E }, // FS_CAL0
{ 0x2F19, 0x03 }, // FS_DIVTWO Divide by 2
{ 0x2F1B, 0x33 }, // FS_DSM0 Digital Synthesizer Module Configuration, Reg 0
{ 0x2F1D, 0x17 }, // FS_DVC0 Divider Chain Configuration, Reg 0
{ 0x2F1F, 0x50 }, // FS_PFD Phase Frequency Detector Configuration
{ 0x2F20, 0x6E }, // FS_PRE Prescaler Configuration
{ 0x2F21, 0x14 }, // FS_REG_DIV_CML
{ 0x2F22, 0xAC }, // FS_SPARE
{ 0x2F27, 0xB4 }, // FS_VCO0 VCO Configuration, Reg 0
{ 0x2F32, 0x0E }, // XOSC5 Crystal Oscillator Configuration, Reg 5
{ 0x2F36, 0x03 }, // XOSC1 Crystal Oscillator Configuration, Reg 1
{ 0x2F8F, 0x48 }, // PARTNUMBER Part Number
{ 0x2F90, 0x21 }, // PARTVERSION Part Revision
{ 0x2F92, 0x10 }, // RX_STATUS RX Status
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I have a spectrum analyzer where I've looked at the output of the transmitter. I also made a software change to the receiver to transmit as well. Both boards are on frequency (within 5kHz but I have a RX bandwidth set to 100kHz) and appear to have a nice peak (the output signal doesn't look "weak").
What else can I look into to see what problem is causing this range problem?
Drew
