On 24/09/15 18:43, Ian Abbott wrote:
On 24/09/15 18:20, Hartley Sweeten wrote:I guess the sign bit would also need to be extended for the bipolar values. So: for (i = 0; i < insn->n; ++i) { unsigned int val = data[i]; /* bipolar ranges use 2's complement values */ if (comedi_range_is_bipolar(s, range)) { val = comedi_offset_munge(s, val); /* extend the sign bit */ if (val > 2048) val |= 0x1000; } /* shift 12-bit data (+sign) to match the register */ val <<= 3; How does that look?It looks okay except that the test for extending the sign bit should be 'if (val >= 2048)'. You could also avoid the conditional and extend the bit regardless: val += (val & 0x800);
Although that assumes that val is in range to start with, otherwise the carry from the '+' might propagate too far. There are various ways to fix that, e.g.:
val |= (val & 0x800) << 1; -- -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=- -=( Web: http://www.mev.co.uk/ )=- _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
