[Grbl_Esp32 Issue#115] Direction pin delay

#1 – bdring 于 2019-04-03

There are probably several ways to do this.

The Grbl way is to use a timer for the delay. That uses up another precious timer, but would probably work.

The ideal ESP32 way is to use the RMT feature. I wrote a blog post on this a while ago. This would allow you to have an OFFONOFF signal with the first 2 stages having a duration. Unfortunately I had a ton of trouble getting the RMT to play nicely in Grbl. The RMT does not like to be called from interrupts. I think this might be due to the API for the RMT. I also had trouble using the RTOS with Grbl to get around that issue. I am not an expert in the RTOS and a lot has changed in the API since I tried this, so there may be hope for the RMT.

I could probably give this another look in a couple weeks after I wrap up some other projects. If anyone knows any experts that could help with this, that would be great too.

#2 – JensHauser 于 2019-04-09

Yes, would be great.

As I have the hardware (DM556 plus 3A stepper on e.g. 1200mm X axis), I can offer to test the programming. Meanwhile I’ll try learning with GRBL on Arduino, although it’s not my preferred solution. ESP32 has much more advantages

#3 – terjeio 于 2019-04-10

Not an expert, however this seems to be working for me:

“
void initRMT (settings_t *settings)
{
rmtitem32t rmtItem[2];

rmtconfigt rmtConfig = {
.rmtmode = RMTMODE_TX,
.clk_div = 20,
.memblocknum = 2,
.txconfig.loopen = false,
.txconfig.carrieren = false,
.txconfig.carrierfreq_hz = 0,
.txconfig.carrierduty_percent = 50,
.txconfig.carrierlevel = 0,
.txconfig.idleoutput_en = true
};

rmtItem[0].duration0 = settings->steppers.pulsedelaymicroseconds ? 4 * settings->steppers.pulsedelaymicroseconds : 1;
rmtItem[0].duration1 = 4 * settings->steppers.pulse_microseconds;
rmtItem[1].duration0 = 0;
rmtItem[1].duration1 = 0;

uint32_t channel;
for(channel = 0; channel < N_AXIS; channel++) { rmtConfig.channel = channel; switch(channel) { case 0: rmtConfig.txconfig.idlelevel = settings->steppers.step_invert.x;
rmtConfig.gpionum = XSTEP_PIN;
break;
case 1:
rmtConfig.txconfig.idlelevel = settings->steppers.step_invert.y;
rmtConfig.gpionum = YSTEP_PIN;
break;
case 2:
rmtConfig.txconfig.idlelevel = settings->steppers.step_invert.z;
rmtConfig.gpionum = ZSTEP_PIN;
break;
}
rmtItem[0].level0 = rmtConfig.txconfig.idlelevel;
rmtItem[0].level1 = !rmtConfig.txconfig.idlelevel;
rmt_config(&rmtConfig);
rmtfilltxitems(rmtConfig.channel, &rmtItem[0], rmtConfig.memblock_num, 0);
}
}
`
and
`
// Set stepper pulse output pins
inline IRAMATTR static void stepperSetStepOutputs (axessignalst stepoutbits)
{
if(step_outbits.x) {
RMT.confch[0].conf1.memrd_rst = 1;
RMT.confch[0].conf1.txstart = 1;
}

if(step_outbits.y) {
RMT.confch[1].conf1.memrd_rst = 1;
RMT.confch[1].conf1.txstart = 1;
}

if(step_outbits.z) {
RMT.confch[2].conf1.memrd_rst = 1;
RMT.confch[2].conf1.txstart = 1;
}
}
“
I write directly to the RMT registers in ISR code, bypassing the API. The code can easily be changed back to the original coding style in grbl.

#4 – bdring 于 2019-04-10

@terjeio

That looks great. I won’t be able to test it until the end of the week, but it looks very similar to what I was going to try.

The API looks like it assumes you intend to change the transmitted data a lot, need to wait for the transmission to complete, and deal with multiple threads.

We want to send the exact same thing each time and the inherent timing of the steps removes all of the other issues.

Your method looks great.

#5 – bdring 于 2019-04-10

I created a

#6 – terjeio 于 2019-04-11

@bdring

That was quick. A minor issue in your branch: since step inversion is done at RMT init it should not be done again in the stepper ISR (line 326). Also, I forgot to include a snippet of code that assigns clock signal to the RMT peripherals – it seems it is not needed as you got it working regardless?
“
uint32_t channel;
for(channel = 0; channel < N_AXIS; channel++) rmtsetsourceclk(channel, RMTBASECLK_APB);
“
I did not add it to initRMT since I call initRMT when settings are changed (I perform basic setup of all peripherals in a separate function).