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Fixed wrong conversion in GDx ADC driver

This commit is contained in:
Silvano Seva 2021-08-15 18:05:23 +02:00
parent 4d3eacc144
commit d329e141ed
1 changed files with 4 additions and 6 deletions
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10
platform/drivers/ADC/ADC0_GDx.c
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@ -64,13 +64,11 @@ uint16_t adc0_getRawSample(uint8_t ch)
uint16_t adc0_getMeasurement(uint8_t ch)
{
/*
* To avoid using floats, we convert the raw ADC sample to mV using 16.16
* fixed point math. The equation for conversion is (sample * 3300)/4096 but,
* since converting the raw ADC sample to 16.16 notation requires a left
* shift by 16 and dividing by 4096 is equivalent to shifting right by 12,
* we just shift left by four and then multiply by 3300.
* ADC data width is 16 bit: to convert from ADC samples to voltage in mV,
* first multiply by 3300 and then divide the result by 65536 by right
* shifting it of 16 positions.
* With respect to using floats, maximum error is -1mV.
*/
uint32_t sample = (adc0_getRawSample(ch) << 4) * 3300;
uint32_t sample = adc0_getRawSample(ch) * 3300;
return ((uint16_t) (sample >> 16));
}