topic ADC module results for MCF52259 in ColdFire/68K Microcontrollers and Processors

ADC module results for MCF52259

eugenia_suarez — Fri, 26 Oct 2018 11:10:48 GMT

I'm testing and analyzing an old project that was built within codewarrior for 7.2 arch and uTasker1.3. So I'm using uTasker ADC libraries. Viewing the adc results and de micro datasheets I have some unclear adc behaviour. I write hoping someone here could bring me some light if I missunderstanding something. The code has a single ended adc bit configured (ADC_0), loop mode and seq mode. Maybe is an uTasker issue. But I would like to have somethings about the MCU's adc cleared.

Reading the datasheet I see that VRefH max could be typically 3.3v. If adc resolution is 12b, I will have 4092 points. This means the maxim value that I can read in result registers is 4092, being equivalent to maximum voltatge input = 3.3V. Isn't it?
Is there any way to get more than 4092 value? I'm reading 21045, for example, so far from 4092!.
Another question I have regarding the ADC block is if it is possible to have much more than 3.3 V to be converted? 5v, 10v, ... ,12v? Since I have understood, Vi converted rank depends on adc VREF max (3.3). But maybe I'm wrong. Could someone validate this?

Thanks in advance.

Re: ADC module results for MCF52259

miduo — Tue, 30 Oct 2018 08:16:25 GMT

Hello,

You did not mentioned any hardware board you used. The NXP evaluation board or customer board. I am not familiar with the uTasker, however I will try to clarify the ADC itself.

First please make sure that

So you should strictly follow the above ADC spec to get an accurate/full range of ADC value, the full scale should be 4095. So back to your questions:

1. yes, 3.3v with a full scale of 4095.

2. No.

3. VREFL<VADIN<VREFH

Re: ADC module results for MCF52259

eugenia_suarez — Tue, 30 Oct 2018 10:31:16 GMT

Hello,

I have just found this information in datasheet for the single ended mode. I think Note 2 and thie following formula would bring some sense to the values I was reading:

So, 111111111111000 is the max ADC value, and 0 when Vin = VREFL (with 4096 possible states between both).