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samd: Reduce a further 48 bytes for non-full builds 

Another reduction of -48 bytes can be had if the fine calculation
step is skipped. The worst difference compared to the old reference
code with my calibration values in the 0° to 60° was 2°C,
and the difference at 25°C is 1°C.

The final size decrease for non-full builds like Trinket M0 is 268
bytes.
This commit is contained in:
Jeff Epler 2022-10-12 15:53:44 -05:00
parent b251e78ac5
commit a943167d69
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GPG Key ID: D5BF15AB975AB4DE
1 changed files with 6 additions and 2 deletions
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8
ports/atmel-samd/common-hal/microcontroller/Processor.c
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@ -122,8 +122,6 @@ STATIC float calculate_temperature(uint16_t raw_value) {
int VADCR = ADCR * INT1VR;
int VADCH = ADCH * INT1VH;
int INT1VM; /* Voltage calculation for reality INT1V value during the ADC conversion */
int VADC = raw_value * 1000;
// Hopefully compiler will remove common subepxressions here.
@ -134,7 +132,10 @@ STATIC float calculate_temperature(uint16_t raw_value) {
// Coarse Temp Calculation by assume INT1V=1V for this ADC conversion
int coarse_temp = tempR + (tempH - tempR) * (VADC - VADCR) / (VADCH - VADCR);
#if CIRCUITPY_FULL_BUILD
// Calculation to find the real INT1V value during the ADC conversion
int INT1VM; /* Voltage calculation for reality INT1V value during the ADC conversion */
INT1VM = INT1VR + (((INT1VH - INT1VR) * (coarse_temp - tempR)) / (tempH - tempR));
int VADCM = raw_value * INT1VM;
@ -143,6 +144,9 @@ STATIC float calculate_temperature(uint16_t raw_value) {
float fine_temp = tempR + (((tempH - tempR) * (VADCM - VADCR)) / (VADCH - VADCR));
return fine_temp / 10;
#else
return coarse_temp / 10.;
#endif
}
#endif // SAMD21