Generating an 8 usec timer interrupt on the LPC804

jrevans — Fri, 20 Oct 2023 13:35:08 GMT

I have some stepper motor control code that I'm porting over from a PIC that uses an 8 usec (micro-seconds) timer (TMR4). To keep the control the same, I need to generate an 8 usec timer interrupt on the LPC804. My target is an LPC804_TSSOP20 which is Part Number LPC804M101JDH20 but I have an LPCXpresso804 Rev B OM40001 board to do testing with.

I was looking at using a CTimer or an MRT timer to generate this 8 usec interrupt and I found an MRT example here on the forum from @jeremyzhou

To test, I'm using the identical code from this posting on my LPCXpresso804 Rev B OM40001 board:
https://community.nxp.com/t5/LPC-Microcontrollers/LPC804-maximum-MRT-frequency/m-p/992300/highlight/true#M39061

But instead of seeing a frequency of 125.7 kHZ and a period of 7.956 us, I'm seeing a frequency of 44.7 kHz and a period of 22.35 us. Any ideas why?

Scope of the MRT timer firing the LED

What would be the best way for me to generate the 8 usec timer interrupt that I need?

Re: Generating an 8 usec timer interrupt on the LPC804

Alice_Yang — Tue, 24 Oct 2023 03:00:56 GMT

Hello @jrevans

Maybe the bus clock not the same with code you mentioned.

You can use Config tool inside MCUXpresso IDE to config timer, after config, it will generated code automatically.

Alice

topic Generating an 8 usec timer interrupt on the LPC804 in LPC Microcontrollers

Generating an 8 usec timer interrupt on the LPC804

Re: Generating an 8 usec timer interrupt on the LPC804