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Hello,
I am currently trying to develop a Hall-sensing EVM with the MSP430FR4133. At the moment I am trying to get stable ADC readings that I can use to display on an LCD display. At the moment I seem to get a non-gaussian distribution of samples for a given input value. Currently I am just using a battery (currently 1.62V) with a RC filter (1k, 10nF) leading to the channel A0. The sample and hold is 256 cycles, ADCCLK = MODOSC, and the clock is divided by 8. When I take 200 samples, I get the following distribution of ADC readings. Would you expect to see this type of distribution in measurements with this particular microcontroller? The Bin values correspond to ADCMEM values. I expect roughly 502-503 for my voltage.
If you suspect layout is an issue. Below is a snippit of my layout. C11 is the 10nF filter cap and C40 is the microcontroller's. Currently the LCD is disabled and not utilized. As of now, the other adjacent ADC channels are grounded. Once this issue troubleshooted though, I intend to use each for a different hall sensor. Top layer polygon pour is VCC and bottom polygon pour is GND.
Thanks Ryan,
That actually fixed my problem. As you can see in the distribution below. There is a little offset, but I think I should be able to calibrate that out.
Also just for anyone else that makes my mistake, if you look at the samples consecutively over time with the wrong bypass cap, you might get sinusoidal-like readings like what I got below:
Thanks Ryan again for the support!
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