Negative value bit shift with bit mask to long

[fedex03]

Hi there,
looking into work library I found a bug into the temperature computation, in particular when the temperature in negative.

if (v & 0x80000000) { // Negative value, drop the lower 18 bits and explicitly extend sign bits. v = 0xFFFFC000 | ((v >> 18) & 0x00003FFFF); }

The bug regards ((v >> 18) & 0x00003FFFF

Here you perform a bit shift of 18 position to maintain the 14 temperature bit, but if you use this mask
0x00003FFFF you maintain 18 bit.

The right operations is to get a negative temperature are:

if (v & 0x80000000) { // Negative value, drop the lower 18 bits and explicitly extend sign bits. v = 0xFFFFC000 | ((v >> 18) & 0x00003FFF); }

Thanks for you work Adafruit!

Best regards,
Federico

[Ve2mrx]

Hi!
Is your issue a duplicate of ##13 ?

Martin

[caternuson]

Should be fixed with #36
https://github.com/adafruit/Adafruit-MAX31855-library/releases/tag/1.1.1