[TriEmbed] MCP3008 issues

[Brian]

Hi Ian,

Without knowing the internal architecture of the chip, I can't say 
whether the every-other behavior is a likely failure mode.  That said, I 
have to say offhand it sounds more likely to be a wiring / assembly 
problem.  Check carefully for cold joints* and solder bridges.  Can you 
post a photo of the front and back of your assembled board?

* Cold joints are identifiable by dull appearance of the solder, and the 
solder appearing to sit on top of the contacts rather than having flowed 
smoothly over them.

HTH,
-Brian

On 7/16/2015 7:51 AM, Ian Hands via TriEmbed wrote:
> Hi all,
>
> I am building something for geekSPARK using an RPI2 and an MCP3008.
> The breadboard testing I was doing worked well (yay!) but now that
> everything is soldered down I am having issues :-(
>
> To explain... I had two of these wired up on a breadboard:
> http://tinyurl.com/npuoz72
> On pins 1, 2. Things were working as expected.
>
> I now have 6 of that same photo resistor + 10k ohm resistor diagram...
> wired to pins 1,2,3,4,5,6 (ch0 - ch5), and things are wonky.
> For some reason I can get good reading from channels 1,3,5 (pins
> 2,4,6) but channels 0,2,4 (pins 1,3,5) are all flat (or damn near
> close to flat).
>
> I am scared that I might have overheated the MCP3008.
> Anyone think heat could cause a failure on every other pin?
>
> It may very well be wiring, but I've gone over everything I think...
> and I am coming up short (pun intended :-D)
>
> I started using example code too... same issue, so I am not suspecting
> the code atm.
> This shows the issue:
> https://github.com/martinohanlon/mcp3008/blob/master/MCP3008.py
> As does this: https://gist.github.com/iphands/b3cd5b329936ed1bb5d5
>
> If anyone has an idea, or if some EE savvy person can help me test
> after work or on Saturday please let me know. I would be very
> greatful.
> Thanks.
>