Pin Toggle Performance

[rosenrot]

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

[ernitron]

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]

Thanks a lot!

[Roberthh]

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]

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!

[Roberthh]

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

[jms]

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

[Roberthh]

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]

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?