Pin Toggle Performance

All ESP8266 boards running MicroPython.
Official boards are the Adafruit Huzzah and Feather boards.
Target audience: MicroPython users with an ESP8266 board.
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rosenrot
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Pin Toggle Performance

Post by rosenrot » Mon Dec 12, 2016 9:41 pm

Hi everyone,

could someone tell me how to toggle the 0 pin the fastest way? I found this post, but it is mostly talking about the STM uC. Maybe someone could tell me how to switch the 0 pin as fast as possible. Maybe with the help of ASM commands?

http://www.mikrocontroller.net/topic/388161

Thanks,

rose

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ernitron
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Location: The Netherlands

Re: Pin Toggle Performance

Post by ernitron » Tue Dec 13, 2016 7:35 pm

Check the topic on sound in here and the reply of pythoncoder. There was a contest on how fast a pin could be set. I am on my mobile and cannot get the link but you can easily find there.

Edit: found
http://forum.micropython.org/viewtopic.php?f=2&t=1349

rosenrot
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Re: Pin Toggle Performance

Post by rosenrot » Tue Dec 13, 2016 7:46 pm

Thanks a lot!

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Roberthh
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Re: Pin Toggle Performance

Post by Roberthh » Tue Dec 13, 2016 8:06 pm

These two links circle around the same contest. More recent for the ESP8266 is the following discussion, even if the title is misleading:
http://forum.micropython.org/viewtopic.php?f=16&t=2678
The answer would be like 21.8 us for a full cycle at 80 MHz, using the native code emitter, with something like:

Code: Select all

@micropython.native
def toggle():
    import machine

    pdsckPin = machine.Pin(4, machine.Pin.OUT, value=0)
    isr = machine.disable_irq()

    for i in range(24):
        pdsckPin.value(1)
        pdsckPin.value(0)

    machine.enable_irq(isr)
Using viper code & direct port access should be much faster.

rosenrot
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Re: Pin Toggle Performance

Post by rosenrot » Tue Dec 13, 2016 10:04 pm

Good, that sounds like there is the possibility to get a full cycle of 250ns. I will try this. Thanks again for linking me further!

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Roberthh
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Re: Pin Toggle Performance

Post by Roberthh » Wed Dec 14, 2016 6:24 am

It's 21.8 µs for each of the 24 cycles, not for all 24 cycles, and the first cycle always takes longer.

jms
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Re: Pin Toggle Performance

Post by jms » Fri Dec 16, 2016 1:20 pm

Since Micropython on this platform executes not much faster than BASIC on a BBC Micro if you want sub 1uS you'll need to write it in C. You could cheat and pretend it's an SPI device and clock out something using that.

Jon

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Roberthh
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Re: Pin Toggle Performance

Post by Roberthh » Sat Dec 17, 2016 3:18 pm

Using viper code and direct register access, you can get a "little bit" faster. The following code example creates a 100 pulse burst with a time of 376 ns between two pulses (or 2.66 MHz) at 80 MHz clock frequency. Using C code or assembler would be a little bit faster

Code: Select all

def toggle():
    import machine
    pdsckPin = machine.Pin(4, machine.Pin.OUT, value=0)
    isr = machine.disable_irq()
    do_toggle()
    machine.enable_irq(isr)

@micropython.viper
def do_toggle():
    GPIO_OUT = ptr32(0x60000300) # GPIO base register
    for i in range(100):
        GPIO_OUT[1] = 0x10 # set bit 4
        GPIO_OUT[2] = 0x10 # clear bit 4
Unrolling the loop results in a period duration of 150ns @ 80MHz.
Update: Setting the CPU clock to 160 MHz does NOT increase the toggle frequency.

poesel
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Joined: Sun Oct 20, 2019 4:58 pm

Re: Pin Toggle Performance

Post by poesel » Sun Jun 21, 2020 10:30 am

Sorry to dig this up.
I failed to find any documentation on this part:
GPIO_OUT = ptr32(0x60000300) # GPIO base register
for i in range(100):
GPIO_OUT[1] = 0x10 # set bit 4
GPIO_OUT[2] = 0x10 # clear bit 4
Is there documentation or is it obsolete by now?

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