AD7705 is 15bit or 16bit ADC

[Darrel Taylor]

write_byte( 0x10 );//Communications Register set to write of setup register
calibration = ADC_SELF, Gain = Unity Input = BIPOLAR and rate of ADC_50(0x04)
setup_adc_device(ADC_SELF,ADC_GAIN_1,ADC_BIPOLAR,A DC_50);
then read the ADC by

It's hard to tell, cause it's a mix of code and suedo code.
But if the 0x04 (shown in red) is what's being sent to the Setup Register, then the device will be in Unipolar mode, instead of Bipolar like the comments say.

But you may get a better answer from a different forum.
We do mostly PicBasic Pro here.

hth,