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Old 05-10-2013, 01:59 AM   #1
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Default Voltages from RX and TX

Hi everyone.

Could someone please tell me wat voltages I should see between Ground and Pins 2 & 3 on the DB9 plug. When not plugged into.the laptop/ usb covertor. But plugged into the MS. Powered up obviously.

I currently have 8 Volts on Pin 2 and 5 volts on pin 3.

Im not sure what I should be seeing. My cable.was riped out of its plug and I cant work.out where to.resolder the wires.

This is a MSPNP running the v3.57 board. If that makes a difference.

I think this test would apply to.any megasquirt with.a serial.comms connection.

Thank you.

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Old 05-10-2013, 10:46 AM   #2
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When communicating, there should be a +12 to -12 volt swing, approximately, as seen on an oscilloscope. Don't try using a multimeter, it's not fast enough to see the pulses.
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Old 05-10-2013, 09:45 PM   #3
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Hi matt.

I ended up working out the fuctions of the four pins on the mini din connector.

Which has allowed me to reconnect the DB9 end
That however is good advice. Turns out I.was getting.confused.from.the 5volt supply for a bluetooth adaptor thinking that was a rs232 signal.


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