PWM individual decoder not working

RE: PWM individual decoder not working

obbe — Wed, 31 Jan 2018 13:54:24 GMT

I guess I interpret that as "single modes require on half word per active channel". What I found unintuitive is that it requires values for channels that are never used.

RE: PWM individual decoder not working

Sigurd — Wed, 31 Jan 2018 13:44:44 GMT

See figure Figure 4. Decoder memory access modes in the documentation. Also from the documentation we have the following:

After the SEQ[n].PTR is set to the desired RAM location, the SEQ[n].CNT register must be set to the number of 16-bit half words in the sequence. It is important to observe that the Grouped and Single modes require one half word per group or one half word per channel respectively, and thus increases RAM size occupation.

Single mode is here the same as Individual mode. I.e. you need one half word for each of the 4 channels, even if you are only using e.g 2 channels. The documentation could have stated this in a more clear way.

RE: PWM individual decoder not working

obbe — Fri, 26 Jan 2018 13:40:50 GMT

Sure, but that doesn't make sense if I only have enabled three of them.

RE: PWM individual decoder not working

micallef25 — Fri, 26 Jan 2018 13:38:56 GMT

my guess is because there are 4 pwm pins grouped together you need to allocate for the 4 registers. I don't recall seeing anything in the documentation

RE: PWM individual decoder not working

obbe — Fri, 26 Jan 2018 07:28:23 GMT

Thanks for this! I spent the better part of yesterday trying to figure this out. Is this mentioned in the documentation somewhere? Because I didn't find anything.

RE: PWM individual decoder not working

micallef25 — Thu, 19 Oct 2017 14:31:12 GMT

That makes sense, Thank you for your help (:

RE: PWM individual decoder not working

Sigurd — Thu, 19 Oct 2017 14:22:36 GMT

When configured as Individual, one duty cycle value is required for each compare register. It have to do with how the PWM is fetching the COMPARE values from RAM.

RE: PWM individual decoder not working

micallef25 — Thu, 19 Oct 2017 13:41:00 GMT

Ok, follow up comment then, why is that??

RE: PWM individual decoder not working

Sigurd — Thu, 19 Oct 2017 13:28:29 GMT

Hi,

For PWM_DECODER_LOAD_Individual, the pwm_sequence table need to be a length of 4.

Change

uint16_t pwm_doody[2]={0x250, 0x421};

uint16_t pwm_doody[4]={0x250, 0x421,0,0};