ACT available

[PANAMATIK]

(04-15-2016 12:20 PM)Harald Wrote:  Hi Bernhard,

no news on the GPS reception so far. I can't tell the difference between how I installed the module at first and the other way round now. I placed the copper foil between the ACT and the module. Did you also ground that? Maybe that would make a difference.

I have flashed the "new" version 107 of the hp25eGPS file. That resulted in an incorrect keyboard mapping. I guess you are now assuming to have an HP25 hardware. Maybe I should swap the hardware - the missing characters in the display driver didn't bother me too much though.

Cheers,
Harald

Hi Harald,

Thanks for the feedback. I still collect experiences for the GPS module. I made some measurements today with my GPS HP-25E (HP-25C hardware, see image below), No copper foil used.

   

Clear blue sky, sunny day, 15:15 to 15:20 UTC (17:15 Uhr MEZ) some clouds, half moon visible, calculator held in left hand, stopwatch in right hand.

From Roof top 100% sky visibility:

Cold Start:
after 50 sec indicating 3 satellites, after 1 Min 10 sec GPS valid with 4 satellites (later 7-8).
Warm start (switched calculator off and on again):
after 11 s GPS valid.

From Garden, approx. 30% sky visibility:
Cold Start:
after 1 min 50 sec 3 satellites, after 1 Min 52 sec GPS valid 4 satellites
Warm start:
after 11 s GPS valid.
Warm start when switched off 30 minutes
after 10 sec one satellite, 20 sec two satellites 28 sec 3 satellites, 42 sec GPS valid

I got feedback from another HP-25E GPS user, who reports also very fast Cold Start times. He additionally uses the copper foil (not grounded). I couldn't comapre directly and don't know for sure, whether the copper foil really increases the sensibility.

If you get 5 minutes Cold Start TTFF, when having clear visibility, then you should find the reason by repositioning your module somehow or find some electrical reason. You should make some experiments to get more sensibility.

Perhaps you can post a picture of your placement?

Keyboard:

The GPS version is intended for HP-25 hardware, therefore I didn't test any other hardware. But normally it should work except for showing different digits in the display. If the keyboard mapping is wrong, then your HP-21 hardware was not detected correctly. The HP-25E reads the external ROM at startup and if HP-21 ROM code is found, the keyboard mapping is adjusted.

Bernhard

Added:
20:15 UTC, Warm Start (after 4 hours switched off) from garden, same position as in the afternoon 30% sky visibility, clear sky, many stars visible (Arcturus in the south) after 30 sec 1 satellite, 3 min 2 satellites 4min 3 satellites, but got no fix until 8 Minutes when I stopped measurement.
20:25 UTC Warm start, moved my location 5 meters away from the house, approx 50% sky visibility, and got GPS data valid after 40 seconds.
The TTFF (Time to first fix) obviously depends highly on the satellite constellation and percentage of sky visibility.