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Topic: interfacing a 12 Bit SPI ADC (Read 12 times) previous topic - next topic

pd2kplus10

  I've been messing around with it for the last couple hours on the correct pins ...  still the same results. I have no idea what may be the problem.



Phil

pd2kplus10

 I'm back to just using this on Arduino.

I'm trying to use the AGND pin. I tried putting about 2V on it, but it just shunts down to millivolts ... since it is an analog ground. Is AGND really meant for setting a lower limit? The spec sheet doesn't really mention too much about it.



Phil

pd2kplus10

 I figured it out. I had to use a separate power source for the analog end of things. I connected the pot wiper (from analog source) to AGND pin.

In the end it brings the resolution down to only 11 bits instead of 12. I have my Vref set to 4.77V (from digital source) and AGND of 2.25V .... my ADC range is from 0 to 2047. Is there any way to make this range from 0 to 4095 ?


P.S.  I didn't connect the Analog ground to the digital ground.


Phil

newbie46

Hi halabut,
I am a newbie with arduino. I'm currently trying to implement ADC MCP3204. I tried to use your code and connect similarly but my adcvalue keeps reading either zero or 4095 (5V). I suspect it's the timing but the datasheet for both 3204 and 3208 have the exact same timing. Please help, thanks!

halabut

That's strange, especially given that they're the same datasheet. Looking at the code it should work fine (for the first four channels only obviously)
All I can advise is checking your connections against the datasheet, the pins are in the same order (except dgnd on the left). Many of my frustrating 'broken' circuits have been me forgetting to connect ground, so check everything twice. Other than that it might (and this is unlikely) be a dud chip.

Alec

-- Alec

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