Micropython + GPIO

[bmarkus]

Each line is 2 bytes long. If you are not closing the file output will be buffered and written at once causing unwanted wave form and timing on the GPIO pin.

Note: did not test with scope or analyzer, so it is just a theory

[bmarkus]

Hi Bela,

Using up stock of my old Model B's.
Latest Luajit and Go not working any more, think they may already be compiled for ARM7, Pi2.

Interesting, will recheck. Thanks for reporting.

[Rich]

Hi bmarkus
Why did you delete my post?

[bmarkus]

Sorry, it was an accident

[Rich]

Hi bmarkus
No problem, I'll recreate it.

[Rich]

Hi gavinmc42

Using your file method, python 2.7 flashes the led at 980Hz, Micropython does 2.8KHz, three times faster.
Maybe because of all the bloat stuff the normal python loads.

You set up the loop like this:

Code: [Select]

fp = open('/sys/class/gpio/gpio22/value', 'w')
while True:
    fp.write('1\n')
    fp.write('0\n')Right? If you include the file open and close commands in the loop it will probably slow things down.

In response to bmarkus's comment:

Each line is 2 bytes long. If you are not closing the file output will be buffered and written at once causing unwanted wave form and timing on the GPIO pin.

Note: did not test with scope or analyzer, so it is just a theory

If that's the case, adding a flush command after each write would be appropriate.

[bmarkus]

If that's the case, adding a flush command after each write would be appropriate.

The MicroPython os module do not have flush() method. You can make os.system('sync') but it is a slow operation. Need testing. Anyhow, MicroPython seems to be a valuable tool.

[gavinmc42]

Smoking,
Micropython 58KHz, about the same for Lua on my multimeter.
Will have to stick CRO on pin to check jitter.

Sort of makes sense, GPIO pin is not really a file.
Probably will have more to do with locking?

Use script to write 16x2 LCD commands.
Some of my boxes really need an ip address display.
Could be a simple solution.
Write only to 5V LCD, can do that with 6 pins and 3.3v I/O.
Hmm PCB redesign.

[bmarkus]

Hi Bela,

Using up stock of my old Model B's.
Latest Luajit and Go not working any more, think they may already be compiled for ARM7, Pi2.
Get an ARM6 expecting ARM7 warning.
Come to think of it maybe I only tested Go on the Pi 2.
Only reason for learning Go is the multicore capability, no need on old Pi's.

Will try the real python.tcz, stay tuned.

GO/LUAJIT issue confirmed, I will fix them.

[gavinmc42]

Thanks Bela,

Interested in Lua because of Luajit.
Near C compiled speeds?

[bmarkus]

A year or so ago we made benchmarks. It was focusing on memory operations, allocations and not a full blown test. Winner was pure C. Next, very close GO and BACON BASIC compiler as a supprize. It was followed by LUAJIT a bit slower. Then far behind Ruby, than PERL and cPython. For sure it may very a bit depending on applications, but first three is expected are C/C++, GO and BACON. That time C# (Mono) was not tested.

[bmarkus]

Latest Luajit and Go not working any more, think they may already be compiled for ARM7, Pi2.

Tested luajit on piCore-7.0alpha3 running on old 'Rev B' RPi:

Code: [Select]

# uname -a
Linux box 4.1.6-piCore+ #1 PREEMPT Fri Aug 28 07:13:51 CEST 2015 armv6l GNU/Linux

# luajit -v
LuaJIT 2.0.3 -- Copyright (C) 2005-2014 Mike Pall. http://luajit.org/

# lua fact.lua
Enter a number:
6
720

# luajit fact.lua
Enter a number:
6
720

# lua hello.lua
Hello World

# luajit hello.lua
Hello World
It works fine as expected. Everything is freshly installed from the repo.

Can you show the case when it fails?


 

[gavinmc42]

I manually installed this version again.
http://distro.ibiblio.org/tinycorelinux/7.x/armv6/tcz/

I might have put the ARM7 version in by mistake.
Luajit is working now, version 2.0.3

file = io.open("/sys/class/gpio/gpio22/value", "w")
while true do
    file:write("1")
    file:flush()
    file:write("0")
    file:flush()
end

Took me a while to figure out that in Lua file write is buffered.
26KHz for Lua, about half speed of micropython because of the two extra file:flush() lines
92KHz same code -> Luajit

[bmarkus]

LuaJIT updated to 2.0.4

[gavinmc42]

Not yet pushed onto
http://distro.ibiblio.org/tinycorelinux/7.x/armv6/tcz/
?

Just noticed I've got old i2c-tools as well.

Micropython is now fast enough to drive a stepper motor, could not do it fast enough in shell.
Had just started designing a Cypress PSoC pcb to do the driving, controlled via i2c.
Now I can do it all on the Pi:)

Not sure if I want to do a three axis controller yet.