BasicMicro - Forums

I suspect I might have damaged my Basic Atom Pro 1, but I don't see how. I can use any of the ADC capable pins to measure a power supply voltage exactly (0-5V). But, it draws around 4-5mA when executing the ADIN statement. Is this normal, or could the pin also be in an output low state at the same time by some programming quirk? Since I need to measure voltage in a high impedance circuit, I can't make the measurement without the Atom Pro 1 dragging the voltage down.

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--scifiguy

I don't know if this is normal or not. The AD pins are also connected to digital I/O pins which are held in an input state when using the AD pins. But drawing 4 to 5ma is a large current draw. If the pins where in an output low state(or high state) you end up with near 0 or near 1023 on the AD reading. What is the source of your analog voltage? Also you should look at the RAenesas datasheet on the 3694 chip. It specifically says the IC is designed for 5k impendance signal sources or less. If impedance is too high your accuracy will be shot. See sections 16.16.1 and 16.16.2 in the 3894 hardware manual.

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Nathan Scherdin
Basic Micro - Robotic Technology Evolved

Thanks, Acidtech. If it turns out this is normal, I'll just have to add a buffer to drive the ADC.

I've tried a few voltage sources--VCC on the Lab Board, an external power supply, and a resistor to VCC. The first two sources result in exactly correct ADC readings. The last has a voltage drop that indicates about 5mA current draw from the source.

I am more and more suspecting that I did something to damage the chip. I have a second on order for another application. When it arrives in a couple days, I'll report what I find.

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--scifiguy

I'm not sure you could damage it in such a way to do this. It's pretty much all or nothing when it comes to these chips. But I guess we'll see in a couple days.

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Nathan Scherdin
Basic Micro - Robotic Technology Evolved

Well, I received the new Basic Atom Pro 1, and it does work better. Now I'm sure my old was was damaged. Where the old one drew about 4-5mA when doing an ADIN, the new one draws 100uA. I still needed to isolate the PWM filter from the ADC pin to prevent loading it too much, but a small MOSFET as a voltage follower did the trick. It can now generate a very accurate voltage by sensing and adjusting the PWM in a feedback control loop. I'm happy now!

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--scifiguy

How old is the old? We did a hardware revision some time ago switching out to a different power regulator.

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Servo Controller - ARC32!

The old one was purchased about six weeks ago. I'm pretty sure it just got zapped.

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--scifiguy