topic Re: Totally off the wall question about I2SRX_CLK in LPC Microcontrollers

Totally off the wall question about I2SRX_CLK

perdrix — Thu, 03 Aug 2023 13:41:12 GMT

I need to generate a 5MHz or 1MHz clock signal (I need both but only one at a time). Among the six pins I have available are P0.23/I2SRX_CLK, P0.24/I2S_WS, and P0.25/I2SRX_SDA

Is it possible to configure I2S to generate a clock signal on the I2SRX_CLK pin? Reading Chapter 20 of the LPC1768 manual suggests that there is a chance that this just might be possible (the figures on page 498 are what made me think that).

If so please could someone show me how it is done. I can afford (just) to sacrifice P0.24/I2S_WS and P0.25/I2SRX_SDA.

Thanks, David

Re: Totally off the wall question about I2SRX_CLK

Miguel04 — Thu, 03 Aug 2023 18:27:01 GMT

Hi @perdrix

Are you refering to use only the clock signal of the I2S without using the peripheral?

Best Regards, Miguel.

Re: Totally off the wall question about I2SRX_CLK

perdrix — Fri, 04 Aug 2023 08:23:20 GMT

Well maybe - if I could work out how to clock data out using that clock - six bits at time, then yes.

If not perhaps I'll just need to bitbang both clock and data and add nops to get the timing right (5MHz clock).

Re: Totally off the wall question about I2SRX_CLK

Miguel04 — Fri, 04 Aug 2023 18:48:21 GMT

Hi @perdrix

I've review the documentation and the user manual does not confirm or deny what you are suggesting, also I found the next text on chapter 20.3 Description:

"When an I2S-bus is active, the word select, receive clock and transmit clock signals are sent continuously by the bus master, while data is sent continuously by the transmitter."

Best Regards, Miguel.