September 14, 2011
about 3 years ago
At first enthusiastic about this board, after testing it for several days I am slightly disappointed. My application is/was to build a PPS-synchronized stratum 0 reference clock based on a EM 406a for a Linux system, connected via serial interface. It now works reliably but the board made it much more difficult than required to get there.
Printed notations like “PPS” on soldering connectors of the GPS-08334 made me believe that the GPS receiver’s PPS signal can be grabbed there. However, this is true only if you connect an EB-85A, but NOT for the EM 406A, so I ended up in soldering a wire to the SMD-mounted connector pin 6 of the EM 406A, this being the only way to connect to the 406A PPS signal. Assuming this is an eval/prototype board, I really miss soldering contacts to connect to unused RS 232 or GPS connector pins.
The following extensions/improvements might be helpful for future releases (really miss them and think that a prototype/eval board should have them):
- on-board soldering pins/holes for ALL unused/non-connected RS232-connector and GPS receiver connector pins, particularly the EM406A PPS pin and the RS232 DCD pin (1), where the Linux drivers expects the PPS signal.
- An on-board LED connected to the PPS signal, flashing on PPS
- Connectivity for +5V (see below)
- For correct functionality, the EM 406A PPS signal must be processed (the PPS pulse is too short to be noticed by the RS232 interface on most computers). I’ve implemented it using a NE555 which is triggered by the PPS signal - it might be worth evaluating such extra functionality on board of the 8334. Btw, connecting to +5V for the NE555 required to solder to the backside of the board, as only +3.3V is available onboard.
I am convinced that these minor improvements could substantially improve the board’s usage. Any thoughts on this?
No public wish lists :(
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