temp calc for negative numbers not correct

[kw123]

the calculation for the pixel values is not correct.
the adafruit spec sheet from panasonic states: https://cdn-learn.adafruit.com/assets/assets/000/043/261/original/Grid-EYE_SPECIFICATIONS%28Reference%29.pdf?1498680225
on page 14

""(11) Temperature Register
Register for reading only to indicate temperature data per 1 pixel.
Temperature Data of each pixel is 12 bit data and 2 byte data.
1 LSB has 12 bit resolution (11 bit + sign) which is equivalent to 0.25℃
and it is indicated as two's complement form.""

the correct conversion should be:

def twoCompl12(self, val):
       if  0x7FF & val == val:
           return float(val)
       else:
           return float(val-4096 )

for the thermistor it is correct

def signedMag12ToFloat(self, val):
       #take first 11 bits as absolute val
       if  0x7FF & val == val:
           return float(val)
       else:
           return  - float(0x7FF & val)

Panasonic has apparently used 2 different forms to do negative numbers for the thermistor and the pixels.

This was tested with ice and in the freezer: the new formula seems to show the proper numbers, using the posted python formulas one gets wrong numbers for negative C surfaces

Karl

[deanm1278]

fixed! thank you!
847541b