HackRF One supports arbitrary sample rates from 2 Msps to 20 Msps. In
early development we had ideas about preferred sample rates that we no
longer consider valid.
The checksum calculation process was causing the CPLD configuration to reload from flash. With the new SRAM loading mechanism, flash contents may not be up to date, so the CPLD bitstream may regress to the point of not working or not working correctly. This commit is a short-term fix for mossmann/hackrf issue #609.
It's using the product string for now, but there are other
things that we could check too. Use -i to ignore the check.
rad1o badge will always pass the check because it uses
"HackRF" as the product string, whichis a substring of both
other devices..
=======================================
This commit allows to synchronise multiple HackRFs with a synchronisation error **below 1 sampling period**
> WARNING: Use this at your own risk. If you don't know what you are doing you may damage your HackRF.
> The author takes no responsability for potential damages
Usage example: synchronise two HackRFs
======================================
1. Chose the master HackRF which will send the synchronisation pulse (HackRF0). HackRF1 will represent the slave hackrf.
2. Retreive the serial number of both HackRFs using `hackrf_info`
3. Use a wire to connect `SYNC_CMD` of HackRF0 to `SYNC_IN` of HackRF0 and HackRF1
4. Run `hackrf_transfer` with the argument `-H 1` to enable hardware synchronisation:
```
$ hackrf_tranfer ... -r rec1.bin -d HackRF1_serial -H 1 | hackrf_transfer ... -r rec0.bin -d HackRF0_serial -H 1
```
rec0.bin and rec1.bin will have a time offset below 1 sampling period.
The 1PPS output of GNSS receivers can be used to synchronise HackRFs even if they are far from each other.
>DON'T APPLY INCOMPATIBLE VOLTAGE LEVELS TO THE CPLD PINS
Signal | Header |Pin | Description
-------|--------|----|------------
`SYNC_IN` | P28 | 16 | Synchronisation pulse input
`SYNC_CMD` | P28 | 15 | Synchronisation pulse output
Note:
=====
I had to remove CPLD-based decimation to use a GPIO for enabling hardware.
More info:
==========
[M. Bartolucci, J. A. Del Peral-Rosado, R. Estatuet-Castillo, J. A. Garcia-Molina, M. Crisci and G. E. Corazza, "Synchronisation of low-cost open source SDRs for navigation applications," 2016 8th ESA Workshop on Satellite Navigation Technologies and European Workshop on GNSS Signals and Signal Processing (NAVITEC), Noordwijk, 2016, pp. 1-7.](http://ieeexplore.ieee.org/document/7849328/)
[Alternative link](http://spcomnav.uab.es/docs/conferences/Bartolucci_NAVITEC_2016.pdf)
