Ergodox - Left hand not working

[kipper]

I assembled my ergodox last night but only my right hand is working. Here's what I've done so far:

* checked that my diodes are the correct direction (that was the solution to the other left-hand-doesn't-work ergodox post)
* I've double and triple-checked all the solder points on the Expander I/O chip
* used a multimeter to check that the TRRS connection from the right hand to the left hand is good (on the TRRS solder joints of both PCBs)
* checked that I get a clean 5V from the Expander I/O chip

Here's a picture of the PCB:
http://imgur.com/a/djH86

Any suggestions on things to test or try would be appreciated!

[plainbriny]

I can't see from the picture,
does your I/O expander in the correct direction?

[kipper]

I can't see from the picture,
does your I/O expander in the correct direction?

Yes, it is. The notch faces the right side.

[OldDataHands]

Try re-flowing all 4 solder joints connecting the
teensy PCB to the 'dox PCB for the TRRS data lines.

Try shorting across a couple of your switches and
diodes just to rule out the diodes in a second way.

Beyond that, your local makerspace should have an
oscilloscope which you can use to identify whether
the I2C bus shows responses from the IOX or not.

You could just try to replace the IOX. Maybe you ESD'd
it to death?

[tricheboars]

i am with these guys. it has to be a problem with the trrs connectors or the io expander.


when i get home i can take a look at your soldering images and let you know what i think.  i cant view these images at work because of the proxy that i helped setup. doh!

[Thechemist]

Did you bridge the two pads on the front side top corner  ( by the I/O Expander )with solder?

[kipper]

Thanks for the reply all! Still no luck..

Try re-flowing all 4 solder joints connecting the
teensy PCB to the 'dox PCB for the TRRS data lines.

Try shorting across a couple of your switches and
diodes just to rule out the diodes in a second way.

Beyond that, your local makerspace should have an
oscilloscope which you can use to identify whether
the I2C bus shows responses from the IOX or not.

You could just try to replace the IOX. Maybe you ESD'd
it to death?

I re-flowed all the solder points on the teensy and confirmed that they are good with the multi-meter. Also shorted the pins but no luck

I need to figure out how to use the oscilloscope but will do this next.

i am with these guys. it has to be a problem with the trrs connectors or the io expander.


when i get home i can take a look at your soldering images and let you know what i think.  i cant view these images at work because of the proxy that i helped setup. doh!

I'm starting to think it's the IO expander. the TRRS connector seems solid - I tested it over the pcbs with a multimeter (though that might not be a definitive test)

Did you bridge the two pads on the front side top corner  ( by the I/O Expander )with solder?

Yep!

[kipper]

Does anyone have a quick guide to using an oscilloscope, more specificially, how to use it for the ergodox? (which pins to put teh plug and do I use the USB port on the oscilloscope?)

[tricheboars]

http://www.digikey.com/product-detail/en/MCP23018-E%2FSP/MCP23018-E%2FSP-ND/1999505

just buy this.  it is the i/o expander in question.  it is less than two bucks.  buy this and swap it out with what you have installed now.  if that doesnt work then get into the oscilloscope.  i am trying to save you time and money.

you will have to desolder your i/o expander you have installed now.  for that kind of work i use this tool:

http://www.amazon.com/Edsyn-Deluxe-Soldapullt-Heavy-Vacuum/dp/B006GOKVKI/ref=pd_sim_sbs_hi_2?ie=UTF8&refRID=0YZABYGEEEGJD8H1X4VA