MATLAB: How to convert 0xffff to -1

Question

I'm controlling a DAC with Matlab. I want to display the voltage that I'm setting the DAC to. The DAC voltage range is from -10 to 10v and the DAC treats the input value as a signed integer. If I cast 0xffff into int16 Matlab gives me maxint (32767) or if I cast into int32 I get 65535.

For example:

DACsetting = hex2dec('ffff')

%Display the setting

fprintf('%d\n', DACsetting * 10/(2^15 -1));

I can write buch of extra code to work around this, but this should be a very simple thing for a language to do.

DACsetting = hex2dec('ffff')

DACsetting =

65535

>> fprintf('%d\n', DACsetting * 10/(2^15-1))

2.000031e+01

fprintf('%d\n', int16(DACsetting) * 10/(2^15-1))

1

Thanks in advance.

Answer 1

typecast(uint16(hex2dec('ffff')), 'int16')