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: <abbo...@mev.co.uk> )=-
-=( Web: http://www.mev.co.uk/ )=-
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