AIN read performance issue

[Sanerix]

I have wrote a small program to read as many requests as possible from AIN0:

from bbio import *
import time

bbio.bbio_init()

i = 0
j = 0
end = time.time() + 1
while time.time() < end:
x = analogRead(AIN0)
if x > 0:
i=i+1
else:
j=j+1
print "have read " ,i , " times in a second with ",j," failed."
bbio.bbio_cleanup()

I get the following output:

root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 307 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 320 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 313 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 318 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 320 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 317 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 318 times in a second with 0 failed.
root@beaglebone:/python# python readAIN1_PyBBIO.py
have read 317 times in a second with 0 failed.
root@beaglebone:~/python# python readAIN1_console.py

when I do the same on Adafruit library, I get

import Adafruit_BBIO.ADC as ADC
import time

ADC.setup()
i = 0
j = 0
end = time.time() + 1
while time.time() < end:
x = ADC.read("AIN1")
if x > 0:
i=i+1
else:
j=j+1
print "have read " ,i , " times in a second with ",j," failed."

root@beaglebone:/python# ./readAIN1_console.py
have read 818 times in a second with 0 failed.
root@beaglebone:/python# ./readAIN1_console.py
have read 822 times in a second with 0 failed.
root@beaglebone:/python# ./readAIN1_console.py
have read 820 times in a second with 0 failed.
root@beaglebone:/python# ./readAIN1_console.py
have read 825 times in a second with 0 failed.
root@beaglebone:~/python# ./readAIN1_console.py
have read 820 times in a second with 0 failed.

So, I figured that you read from sysfs, are you still having plans for reading AIN0 from memory? Is there any way to get more reads per second?

[alexanderhiam]

Thanks, that's good info. Both PyBBIO and Adafruit_BBIO are using the sysfs drivers. The difference is that Adafruit is using a C extension to do the file I/O, where as PyBBIO is currently doing file I/O straight from Python. I did it that way because it was the quickest way to get the ADC working, but I am planning on moving more of the IO to C extensions as I find the time.

I suppose it would still be possible to directly control the ADC the way I was on earlier kernels, but the problem is it then wouldn't be compatible with any overlays that use the ADC, because the iio driver would just reconfigure it. One of my goals is to make PyBBIO as cape compatible as possible, so it has to be able to work along side the iio driver. I'm still looking into how best to do this.

[Sanerix]

In new kernels there is now a fix for AM335x_ADC_Driver that provides continuous sampling support
link: http://thread.gmane.org/gmane.linux.kernel.input/32024
blog: http://beagleboard-gsoc13.blogspot.nl/2013/09/success-at-last.html

Would be awesome to have same functionality in python. May be worth to consider?

[alexanderhiam]

Thanks for pointing that out. It would definitely be cool to support continuous mode in PyBBIO to get some faster sampling, perhaps even combined with epoll to fire a callback after every sample. I definitely want to get the normal ADC reads faster first though.

[alexanderhiam]

I'm closing this issue as I'm not planning on changing the way analogRead() works any time soon.

[ghost]

Where can i find 'adafruit_bbio.adc'; i was interested to know the definitions of 'adc.read', 'adc.read_raw'

[deepakkarki]

This is the wrong repository.
You are looking for adafruit.bbio and not PyBBIO

[ghost]

Ok.. Problem was solved.. Thanks

-----Original Message-----
From: "Deepak Karki" notifications@github.com
Sent: ‎06-‎04-‎2015 15:13
To: "graycatlabs/PyBBIO" PyBBIO@noreply.github.com
Cc: "Advanta09" advaitjavadekar@gmail.com
Subject: Re: [PyBBIO] AIN read performance issue (#29)

This is the wrong repository.
You are looking for adafruit.bbio and not PyBBIO
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