EFM32: Scaling of analogin_read incorrect

[seppestas]

Description

• Type: Bug
• Priority: Minor

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Bug

Target
EFM32

Expected behavior
AnalogIn::read should return a value from 0.0 to 1.0

Actual behavior
AnalogIn::read returns a value from 0.0 to 0xFFF0/0XFFFF = 0,99977111467155.

Cause
analogin_read_u16 returns a value in the range 0x0000 - 0xFFF0 since the resolution of the ADC is 12 bits. However, in analogin_read this value gets divided by 0xFFFF assuming the range is 0x0000-0xFFFF. This causes a small error in the value returned by AnalogIn::read for the EFM32 target.

[0xc0170]

cc @stevew817 @akselsm

[seppestas]

Ow right, I was planning to send a PR for this... Totally forgot XD.