GPS and 28X/28X1

[JanJor]

Dear Picaxe community,
the following program (see below) works perfect with my two 18X-boards, but neither with my 28X board nor my 28X1 board. If I run the program at setfreq m8 (18X) and adapt the baud rate it also works fine (better, because longer recognition strings can be read).
If I run the 28X at 8 or 16 MHz (external res.) or the 28X1 at setfreq EM8 or EM16 (external res.), nothing happens.

Even if I leave out the recognition string ("C,"), nothing happens with the 28X1.

Download is OK, and the boards have been used in many settings and occasions and I never experiences any troubles. Power: 5 V stabilised including C's.

Anyone with an idea/advice, or recognising this problem?
Thanks in advance for your help.
Ronald

gps:
serin 0,n4800,("C,"),b1,b2,b3,b4,b5,b6
sertxd (b1,b2," uur, ",b3,b4," minuten en ",b5,b6," seconden",13,10)
goto gps

 

[Shack]

Check your pin numbers to be sure they are using the correct physical pin on the respective chip.

 

[hippy]

Thinks, but cannot answer ... Is this a case of another 28X1 baud rate issue ?

 

[Technical]

Take out the ("C,") qualifier. If you still get nothing at all happening then there is a hardware issue, you should get at least some data in - if the baud rate was incorrect it would be garbled data - but at least you should get something!

As both 28X and 28X1 both fail to work this also implies a hardware issue.

 

[demonicpicaxeguy]

has the picaxe in question been used for any other project? if so what

 

[JanJor]

Technical, Demonic.. leaving the "C,"out gives indeed garbled data, with the 28X, but only if I use a 2.7 k pull-up resistor connected to the inport. If I leave that out, it does not respond at all. Anyway, the input ports are all correctly functioning (I protect them with 200 ohm resistors in series with each port) The 28X runs with a 4 MHz resonator, the 28X1 runs with 4, 8 or 16 MHz resonators, I tested all of these, so that can't be the problem. The scope shows the normal (although not easy to interprete) GPS-output signal.
Remains puzzling, doesn't it?

Ronald

 

[Technical]

Is it a 3.3V GPS, if so try dropping the PICAXE supply to 4V.

 

[demonicpicaxeguy]

you might find the the lack of a buffer might be the cause of this problem, basically the picaxe can recieve 1 byte ok but because it doesn't have a buffer it can't be ready to recieve the next few bytes in time this would be where the hardware serial module comes in