Discussions

I have a MediaTek GPS, attached to Ardupilot Mega + Oilpan, which I bought around Spring 2011, and last used around that time.  

The MediaTek GPS does not work when the Oilpan  (FoxTrap 2.2, 5/24/2010)  is plugged in.

I followed the instructions on the wiki to update the to 1.6 (Firmware AXN1.30_2389_3329_384.1151100.1_v16.bin).

When I attach the GPS to the computer with a FTDI cable, and I can see good serial data at 38400 bps.   I can also use the "MiniGPS 1.4" tool to get my latitude and satellite info.

(Image at right illustrates the 3.3V FTDI-cable setup that gives me good serial data)

If I have the MediaTek GPS hooked up to the Ardupilot Mega, the serial stream is no longer good.

I have tried the "GPS MTK library test" sketch from the latest git pull (this afternoon), but it returns 

GPS MTK library test

and no data.

To figure out what my Ardupilot is reading from the MediaTek GPS, I wrote a test sketch (for Arduino Mega 1280) to pass through serial data from the MediaTek GPS to my serial port.

The Arduino sketch:

void setup()
{
    Serial.begin(115200); /* COM3 */
    Serial1.begin(38400); /* MediaTek should be here */
    Serial.println("GPS MTK pass-through test"); /* some ASCII */
}

void loop()
{
    if (Serial1.available()) {
        Serial.write(Serial1.read()); /* pass through */
    }
}

I end up getting: 

GPS MTK library test
ìplb|âübbcbcbbbbpcpcll`ìlbpübbbbbcbcbbbbbbãllllìlrsblüb|âccbbbbbüccbpìpbbâ|cblìbcübbcpbblcãbbpll`ìplìb|âüàbbbcbbbbbpbpbl`ìlbpüppbcbbbbcbcbcbbâllllìlssblüìb|âbbbbbccübcbpìpbcâ|bcrrlìcbübbbpbblbâbbpll`ìplb|âüàbbbbccbbbpcpbìlìlbpücbbbbbbcbcbbbbãllllìlbpplâb|slìlrrblüc|âbbcbcbü|ccbpìpâpcll`ìbü|bbcpbclãbbbpll`

When I hook it up to the FTDI again, I get nice serial output at 38400:

$GPGGA,021159.000,3354.9162,N,11805.1101,W,1,7,1.11,94.1,M,-33.9,M,,*5F
$GPGSA,A,3,12,02,29,10,25,04,09,,,,,,1.40,1.11,0.85*0A
$GPRMC,021159.000,A,3354.9162,N,11805.1101,W,0.10,148.10,150712,,,A*7E
$GPVTG,148.10,T,,M,0.10,N,0.19,K,A*38
$GPGGA,021200.000,3354.9166,N,11805.1108,W,1,7,1.11,92.6,M,-33.9,M,,*5C
$GPGSA,A,3,12,02,29,10,25,04,09,,,,,,1.39,1.11,0.85*04
$GPGSV,3,1,10,12,86,307,36,02,64,038,39,48,47,205,29,25,42,316,30*72
$GPGSV,3,2,10,05,38,140,,10,32,071,31,29,27,291,26,04,23,047,31*72
$GPGSV,3,3,10,09,19,204,21,27,13,198,*7B

I've tried swapping the cable with a new one, and I'm plugging it into the Ardupilot Mega jack (not the OilPan connector that says "No GPS")

I've tried the "warm start", but the reset button on the OilPan doesn't seem to work (I don't get a new line "GPS MTK library test" on press).

It's like the singing frog -- when I show it to the Arduino, it's a frog, when I look at it alone, it sings.

.....................

Update: If I unplug the OilPan (FoxTrap 2.2, 5/24/2010), and plug a 3.3V FTDI cable into the board, i get good data from my sketch.  When I try to go through the FTDI chip on the OilPan, I get bad GPS characters.

.....................

Does this behavior make sense to anybody here?  I'll continue to search the forums, but I figure somebody on this group might have experienced this problem before.

Thank you!

-John