Compiler/CC2541: CC2541 ADC conversion issue

Robert John Dichos

Intellectual 650 points

Part Number: CC2541

Tool/software: TI C/C++ Compiler

Good Day,

I just had an issue regarding ADC for cc2541.

The maximum 8bit value i get is only 0x7F or 127 when I supply VCC or 3.3 to the channel 7 analog input.

My settings are HalADCSetreference (HAL_ADCREF_AVDD) and adc = HalADCRead(HAL_ADC_CHN_AIN7, HAL_ADC_RESOLUTION_8).

Have I missed something here?

Thanks.

over 9 years ago

0 Fredrik K over 9 years ago

TI__Guru** 106705 points

Hi Robert,

This is because the result is signed and can be both positive and negative (even though negative input is not supported). Refer to chapter 12.2.5 in the User´s Guide for details.

Cheers,
Fredrik

0 YiKai Chen over 9 years ago

Guru 735695 points

Try to refer to sunmaysky.blogspot.tw/.../cc2530-adc-howto-in-ti-z-stack.html

0 Robert John Dichos over 9 years ago in reply to Fredrik K

Intellectual 650 points

I see.. so does this means i can only have half the total range of any resolution i set with the ADC (ex. 8bit 0-127, 10bit 0-511 and so on...)? am i correct to assume this?
Thanks.

0 YiKai Chen over 9 years ago in reply to Robert John Dichos

Guru 735695 points

It's 2's complement so the answer is yes.

0 Robert John Dichos over 9 years ago in reply to YiKai Chen

Intellectual 650 points

Thanks for the verification.

0 YiKai Chen over 9 years ago in reply to Robert John Dichos

Guru 735695 points

You are welcome.

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Compiler/CC2541: CC2541 ADC conversion issue