topic Re: LPC11C14 CAN and UART Pins in LPC Microcontrollers

LPC11C14 CAN and UART Pins

satbir7 — Thu, 24 Aug 2017 17:43:23 GMT

Hello All,

Currently, on LPC11C14, I have the CAN TXD/RXD pins connected to the corresponding UART TXD/RXD pins, and have been using the UART without any issues. The idea was to be able use either the UART or CAN controller.

The datasheet says that the default state of the CAN TXD pin is HIGH, so how is my UART working?

Won't there be a short when the UART TX pin pulls the line down?

Would this setup be an issue if I had to program the chip in ISP mode ?

Thanks,

Satbir

Re: LPC11C14 CAN and UART Pins

jeremyzhou — Fri, 25 Aug 2017 02:23:48 GMT

Hi Satbir Sekhon,

Thank you for your interest in NXP Semiconductor products and

for the opportunity to serve you.

I'm very curious about why you connect CAN TXD/RXD pins connected to UART TXD/RXD pins, whether you can introduce the purpose of this implementation.

Have a great day,

TIC

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Re: LPC11C14 CAN and UART Pins

satbir7 — Fri, 25 Aug 2017 02:39:45 GMT

Hello Jeremy,

Thanks for the reply.

The idea behind connecting the CAN and UART pins together, is to be able use either UART or CAN using just one physical transceiver chip.

Satbir

Re: LPC11C14 CAN and UART Pins

jeremyzhou — Fri, 25 Aug 2017 06:19:10 GMT

Hi Satbir Sekhon，

Thanks for your reply.

My suggestion is disabling another module when one module is active, however you need to do some testing to evaluate the risk.
Have a great day,
TIC

Re: LPC11C14 CAN and UART Pins

satbir7 — Fri, 25 Aug 2017 16:22:22 GMT

Jeremy,

How can the CAN module be disabled ?

I know that the UART pins can be easily be set to input mode.

Thanks,

Satbir

Re: LPC11C14 CAN and UART Pins

jeremyzhou — Mon, 28 Aug 2017 01:41:30 GMT

Hi Satbir Sekhon，

To disabling the CAN block, you can reset the CAN block via asset the bit3 in the PRESETCTRL register, then dis-asset the bit 17 in the SYSAHBCLKCTRL register.

Hope this is clear.
Have a great day,
TIC