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Baro went dead after soldering new mag to oilpan.. Strange one..

Posted by Mike R. on July 18, 2012 at 6:54pm

Greetings all,

  In my quest to try to save my oilpan while I await a new mega 2 shipment, I have run into a strange issue..

I replaced the mag (compass) on the oilpan as it somehow went up in smoke during another strange incident involving a bad XBee carrier board I purchased from a 3DR distributor just over the boarder.. At the time, the compass was giving crazy readings (always spinning) so I replaced it - all is well with the compass, but now the baro isn't working at all.. CLI shows max pressure, 0cm height, and max temp..

I looked up the datasheet and have the schematics for not only the IMU but also the baro/temp breakout board 3DR sells, and after tracing and testing the pins for continuity to the rest of the board (and they are good..) I can't figure out what could be the issue.. 

Steps taken:

1. Bad carrier board for XBee did something to screw up mega 1 board and IMU shield
 - no longer doing anything...

2. Kickstarted a reload of bootloader and firmware using Arduino IDE and FTDI cable.. It's alive!


3. Figure out through CLI testing that everything works great (with 2nd new XBee board) except compass..

4. Order new compass, and solder to board - happy new compass..

5. Test flew, noticed crazy behavior after getting ~15 feet up (out of sonar range)

6. Tested baro in CLI, max scale readings for pressure and temp, nothing for altitude.

As it died when I put the new compass on, I don't want to de-solder the compass to test (more important to have compass than baro at the moment) as many people burn up the solder pads, and I don't want to chance it.. I can't figure out what could have happened, as the board looks good, no issues with solder, etc.. Heat from a second of soldering the compass shouldn't have done anything, and continuity test looks good for each pin - although I notice on the imu schematic xclr isn't connected to anything on the bosch baro, but it has a hole for wire on the breakout board that 3dr sells.. so don't know if it's just not used on the IMU, or it's a mistake on the schematic labeling..

Any other ideas would be greatly appreciated..

Thanks!

Mike

PS - This is the output I currently get in CLI when I'm in the altitude test:

alt: 0cm, pres: 319213mbar, temp: 2054/100degC, raw pres: 0, raw temp: 65535

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Tags: baro, compass, imu, oilpan
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Replies

  • Cliff-E July 18, 2012 at 7:31pm

    Do you have 5V on the compass, 5V on the baro?The i2C bus (which both sensors are on) is pretty sensitive to voltage. You need at least 4.98V.

    Make sure the compass has no EMI around it--it's location is too sensitive to EMI IMO.

    Also make sure the Xbee is far away from the oil pan.

    Also IF you know how, you can tap the SDA/SCL pins on the red board (under the compass basically) and put the signal on a scope to see if it's truly flatlined/dead.

    Also if you're willing--buy a baro-explorer type board with the same sensor, plug it into the I2C port (will need to move compass?) and modify the code to ignore the onboard baro (hard).

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