14M2 - generating a square wave on one pin - hpwm?

[ferrymanr]

I need to generate a square wave on one pin of a 14M2 so I can derive a low current negative voltage rail. This needs to run continuously as a background task. Is hpwm the best option? If so am I restricred to using hpwm D (B.5) as the output? Unfortunately using B.5 makes my board layout a bit messy as B.1 to B.5 curently go straight to an adjacent darlington relay driver array :-(
Thanks
Rickard

 

[Dippy]

Mmm... well I hope you haven't spent hours making a board and only thought of this now
(We've all done it...).

Is this for a GLCD? If so are you sure that the driver isn't on-board?

Alternatively, you may be able to use a DCDC voltage inverter charge-pumpy thing.
(Or a second battery).

 

[AllyCat]

Hi,

I believe the "H" in HPWM actually stands for "H-bridge" and all the PWM outputs are generated by on-chip hardware. So you should be able to use any PWM output pin (the HPWMs are actually more restrictive because they're mainly intended to be used a group).

Cheers, Alan.

 

[ferrymanr]

Thanks Alan. I will try pwm instead. I thought that hpwm was a background task like hser. Didn't think of it being an H-bridge.
DC-DC converters are overkill when I just need a milliamp or so of negative bias. Square wave to a couple of diodes and capacitors and that will give around -4.5V which is all I need. Output C.0 is not in use so can use that - and there is space to do a lashup on the PCB.
Regards
Richard