topic Re: LPC811 pin inversion in LPC Microcontrollers

LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:30 GMT

Content originally posted in LPCWare by mattiad on Wed Feb 18 09:57:42 MST 2015
Dear All,

I'm using an LPC811 to communicate via UART. My goal is to communicate via UART with both TX and RX lines inverted. I read on the user manual that an input pin can be easily inverted (setting a register) but I haven't found anything about inverting the output (my tx line).

Do you have any suggestion?

Thanks a lot,

Mattia

Re: LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:31 GMT

Content originally posted in LPCWare by Wouter on Wed Feb 18 10:23:00 MST 2015
Hi Mattia,

The UART Rx can indeed be inverted by activating the INV bit in the pin's IOCON register. Unfortunately we do not have such an option for the Tx pin.

Why do you want to invert your UART signals? Normally you either use TTL UART signals (as the LPC uses), or RS232 compatible signals, which could be considered inverted. Usually there is no use for using inverted UART TTL signals.

Regards,
Wouter

Re: LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:31 GMT

Content originally posted in LPCWare by mattiad on Thu Feb 19 00:35:02 MST 2015
Hi Wouter,

I have to communicate with an external device which uses an inverted ttl UART. Since I can't change its signals, I need an UART inversion and probably I have to invert it before it arrives to micro's pins.

Thank you very much,

Mattia

Re: LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:32 GMT

Content originally posted in LPCWare by Wouter on Thu Feb 19 09:40:57 MST 2015
Hmm, I see. If there is no way to change the behavior of the other device, then I'm afraid there's no other solution then to use external hardware to do the inversion for you.

Re: LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:33 GMT

Content originally posted in LPCWare by djrose on Thu Feb 19 11:25:36 MST 2015
Maybe the 811 is different to the 812 in this regard.

I remember seeing this before though:

http://www.lpcware.com/content/forum/can-lpc812-invert-uart-rx-input

Re: LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:33 GMT

Content originally posted in LPCWare by Wouter on Thu Feb 19 14:05:59 MST 2015
Thanks, I just checked on one of the actual boards, and the INV bit indeed also applies when the pin is configured for UART Rx.
Sorry for the confusion, I've edited my post above to make it clear from anyone new to this thread.

Re: LPC811 pin inversion

lpcware — Wed, 15 Jun 2016 20:05:34 GMT

Content originally posted in LPCWare by Andy1325 on Thu Feb 19 16:28:11 MST 2015
Would it be possible to use Pattern Match Engine to invert the TX line? (if it's not used at the moment and the possible clock delay would not be a problem). I haven't tried this but it was just one thing that maybe could be done.