[TriEmbed] MCP3008 issues

[Carl Nobile]

Sorry for the late response, when I got your email I was very busy and then
forgot about it till now.

I doubt that you over heated the chip. These things can take a lot of heat,
remember they are meant to go through a wave soldering machine.

You might want to look at pin 11 the Din pin. If it's not being pulled down
or up when it's supposed to you might get this kind of result. Also, look
at 10 the CS pin, this may have similar results. In either of these cases
check if the pin is being held high or low all the time.

Carl




On Thu, Jul 16, 2015 at 10:02 AM, Brian via TriEmbed <triembed at triembed.org>
wrote:

> 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.
>>
>>
>
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-- 
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Carl J. Nobile (Software Engineer)
carl.nobile at gmail.com
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