DIY: Simple PSP-GPS hookup

[jyhuh]

NVM IT WORKS!!!! I never expected it to work. I just had to put the replay equal to 0. yea, anyway, thanks for all the help

[vibez]

welcome to the party

[ZeroAltitude]

Hello,

I feel like I'm 90% there with this hookup on a Garmin eMap (circa 1998). That GPS supports (allegedly) NMEA @ 4800 baud. It's a 3V device. The pinouts are very easy.

I've hooked one up following roughly the outlines Deniska and others have posted. Apparently no resistor is required, and the PSP *does* get data on the serial port (I used gpsviewer, recompiled with 4800 baud setting).

My problem is that the data is just a bunch of deterministic, repeating high-bit ascii characters which are obviously not NMEA sentences.

I noticed that others have had this same problem -- any help or advice you could offer me? I'm wondering if I've recompiled the proggie wrong @4800 -- you just change the pspDebugSioSetBaud() statement right? Do you also have to modify the sceKernelDelayThread(20) in the loop to get accurate timing?

Again, thank you for listening -- hopefully someone has the silver bullet -- til then, I'll keep hacking away til it works

ZeroAltitude

[A Fn NOOB]

Can u post a screenshot of the output with "greenscreen"?

Do you have specs for the unit handy?

Search the site for a version of greenscreen I posted up for 4800 baud, its on here somewhere, but I think out in the News forum.

Sounds like either your unit is configured for other than 4800, or bad compile. But getting it working in "Greenscreen" first is the best thing to do, so you can rule out config problem with the reciever. (Maybe greenscreen could integrated into MapThis to aid in configuring one day)

Also some GPS specs make it confusing as to which pin is RX & TX...... Make sure that:


GPS TX ---> Serial RX


If the data appears to have some consistency ( Like repeating similar characters every 20 secs) look at the bitrate.
If it doesnt, maybe wires are crossed.

Edit: I didnt realize that it was a handheld (as opposed to a gps-'mouse'... I bet there is a menu in it's GUI to change from it's native Garmin protocol to NMEA sentences. Most likely the problem.

[ZeroAltitude]

Hi there,

Thank you for the quick reply! It is possible the wires are crossed, but the consistent visible data seems to indicate that might not be the issue. I have made sure in the setup program to set it to NMEA (it was the default, but you're right there are other protocols, some Garmin proprietary).

If I can't get it working in a few more go-s, I'll see if I messed up the wiring (I did (try?) to do TX > RX as specified -- I'll have to look at the specs again maybe!).

Thank you again, and if you get any other thoughts, I'll be watching this thread intently!

~0

[ZeroAltitude]

Re: specs:

http://www.gpsinformation.org/dale/tech.htm

http://www.garmin.com/products/emap/spec.html
(and linked PDF)

~0

[A Fn NOOB]

Heres what Id do to rule out the wiring first

Get luaplayer, it has a serial port program included that gives raw data from serial port. It is limited to 2400 baud though. No problem, set your emap to text output and 2400 baud.

Thats just what Id do. Im assuming the emap will let you change baud in some protocols like my Garmin Etrex does, from 1200 to 9600. NMEA is locked at 4800 on the EtrexLegend. 4800 seems to be the industry standard speed for most GPS's. (4800 baud is also the default speed of the PSP serial port, I recall)

Then look for a post by my where I included the EBOOT where I changed it to 4800, it works for sure.

Good luck... you'll have this solved in no time.

[ZeroAltitude]

BINGO! I *think* one of Deniska's wiring diagrams on his site might be wrong: I reversed the wires (GPS TXD > PSP pin *2* -- listed as GND, I believe maybe RX and GPS GND > PSP pin *6* -- listed as RX, I belive maybe GND?)

Either that, or the Garmin spec is wrong >< (i *was* getting - voltage when using my multi in a way i thought should give + voltage)

Either that, or I'm dyslexic )

Now it works! Thank you so much for your patience and help NOOB and Deniska (on another thread).

~0

To sum up:

Garmin eMap
Wire pin 3 to PSP pin *2*,
Wire pin 4 to PSP pin *6*,
no resistors needed,
set Setup to NMEA 4800
and voila

[deniska]

great!!!
I am glad it worked out for you...

I think my diagram is correct though..
at least there are a few more sources (aside from obvious "it works for me") confirming the pin layout..
This is just one of them:
http://nil.rpc1.org/psp/files/PSP%20...0Converter.pdf

I hope you'll be able to hook it up with MapThis! (if you have not already done so)
You may need to get the latest eboot from friday (attached to one of the threads here) to make it work - since I increased the NMEA buffer for "slow baud devices"...

[ZeroAltitude]

I agree -- since you got it working on the Holux, and since others have as well with your pin diagram, something else must be wonky. It's very puzzling.

I'm setting up MapThis! right now! More soon

~0