Marco Menchise

Generating precise non periodic digital waveform using MCF52235 MPU

Discussion created by Marco Menchise on Apr 1, 2008
Latest reply on Apr 2, 2008 by Bryan Kattwinkel

I need to generate a digital non periodic waveform on an output pin of the MCF 52235 MPU and CW 6.3.

First, I tried using QSPI, but i discovered that I cannot generate burst longer than 16 pulses without delays between them; then I tried disabling interrupts and using GPIO driven from assembler instructions... but, again, no luck because the GPIO module clock is not correlated with main processor clock, so there is a random skew in the generated waveform (2 or 4 CPU clock skew).

Now, I'm trying using DMA timer.. I plan to store the waveform in RAM as a buffer of delays, then start the timer and allow it to read  the counter register from the buffer using DMA. This way, maybe, I'll get the waveform. But there's no code example showing how to use DMA timers. I searched the documentation and the forum and I found nothing.

Could someone please help me, maybe posting some code fragment?

Any suggestion will be appreciated,