diff options
Diffstat (limited to 'usrp2/firmware/lib')
| -rw-r--r-- | usrp2/firmware/lib/db_bitshark_rx.c | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/usrp2/firmware/lib/db_bitshark_rx.c b/usrp2/firmware/lib/db_bitshark_rx.c index 4c126de9b..cf7370ff0 100644 --- a/usrp2/firmware/lib/db_bitshark_rx.c +++ b/usrp2/firmware/lib/db_bitshark_rx.c @@ -181,15 +181,39 @@ bitshark_rx_set_freq(struct db_base *dbb, u2_fxpt_freq_t freq, u2_fxpt_freq_t *d struct db_bitshark_rx_dummy *db = (struct db_bitshark_rx_dummy *) dbb; unsigned char args[NUM_BYTES_IN_I2C_CMD]; unsigned char val[4]; - uint32_t freq_in_khz = (uint32_t)(u2_fxpt_freq_round_to_uint(freq)/1000); - + uint32_t freq_in_hz = (uint32_t)(u2_fxpt_freq_round_to_uint(freq)); + uint32_t freq_div_5mhz = freq_in_hz/5000000; + uint32_t freq_rounded_to_5mhz_in_khz = freq_div_5mhz*5000; + uint64_t freq_rounded_to_5mhz_in_hz = ((uint64_t)freq_rounded_to_5mhz_in_khz)*1000; + uint64_t temp; + if(!(freq>=db->base.freq_min && freq<=db->base.freq_max)) { return false; } + + /* There is a bug in the BURX firmware where tuning to frequencies + above 2.2 GHz will result in a small final frequency error + (up to a few KHz). This bug is due to an overflow of a 16-bit + value when the input reference clock is sufficiently high (such + as the 100 MHz clock used on the USRP2), AND the requested tuning + frequency is not a multiple of 5 MHz. A fix for the BURX firmware + is available from Epiq Solutions, but requires an AVR microcontroller + programmer to update the firmware on the BURX card directly. An + alternate solution is to enforce a policy where the BURX card only + tunes to frequencies that are multiples of 5 MHz, and uses the + DDC in the FPGA to perform any fine-tuning less than 5 MHz. So + an application can still request an abribrary RF tuning frequency, + but the BURX card will be directed to tune to the next lowest + multiple of 5 MHz, and return the DC-centered freq to the calling + function to allow the DDC in the FPGA to perform the final + down-conversion digitally. This policy also reduces the overall + spurious content due to the LO synthesizer, as the Frac-N portion + of the ADF4350 synthesizer isn't being invoked in modes where + high spur content would be seen. */ memset(args,0x00,NUM_BYTES_IN_I2C_CMD); - memcpy(val,&freq_in_khz,4); + memcpy(val,&freq_rounded_to_5mhz_in_khz,4); args[0] = RF_CENTER_FREQ_REG; args[5] = val[3]; args[6] = val[2]; @@ -211,7 +235,13 @@ bitshark_rx_set_freq(struct db_base *dbb, u2_fxpt_freq_t freq, u2_fxpt_freq_t *d delays too, but this seems to be stable. */ mdelay(5); - *dc = freq; + /* shift the value up so that it is represented properly in the fixed + point mode... + */ + temp = freq_rounded_to_5mhz_in_hz << U2_FPF_RP; + + + *dc = (u2_fxpt_freq_t)temp; return true; } |