@jcaron I think that this was @tttadam's conclusion.

Never mind I found the problem. It was actually in the line above paramVal = self._device.readfrom_mem(self._address, SI1145_REG_PARAMRD, 1)

@robert-hh my bad, you're right >>> type(s.split(b'|')[0]) <class 'bytes'> >>> type(str(s).split('|')[0]) <class 'str'>