Dawn Robotics Forum

Re: Unable to connect to Firmata

2015-01-28T00:15:30+01:00

Hi Max,

I can see that there's a potential bug in PyMata (the line that reads 'Error: Caught exception in command handler - pop from an empty deque') but I'm not going to have a chance to fix it until Friday.

In the meantime I think that you problem may be happening because the serial communication with the Pi Co-op is not being shutdown properly when your script ends (again, another possible bug in PyMata).

Could you please try running your script again, and then after it's finished could you please run

Code:: lsof /dev/ttyS0

which should show you if any program is still using the GPIO serial port. You may need to run

Code:: sudo apt-get install lsof

to install lsof if it isn't already there.

Regards

Alan

Statistics: Posted by Alan — Wed Jan 28, 2015 12:15 am

Re: Unable to connect to Firmata

2015-01-27T11:35:14+01:00

Hi Max,

Sorry, very embarrased here, this completely slipped my mind.

I'll look at this today and give you an update this evening.

Regards

Alan

Statistics: Posted by Alan — Tue Jan 27, 2015 11:35 am

Re: Unable to connect to Firmata

2015-01-26T22:11:32+01:00

Evening Alan,

Did you get a chance to look at it?

Max

Statistics: Posted by Maximus789 — Mon Jan 26, 2015 10:11 pm

Re: Unable to connect to Firmata

2014-12-30T22:52:13+01:00

Hi there,

Thank you for this.

I can't see anything obvious after a quick look at the code, but I'll try running it when I get back in to the office next week (5th January) and let you know if I find anything.

Regards

Alan

Statistics: Posted by Alan — Tue Dec 30, 2014 10:52 pm

Re: Unable to connect to Firmata

2014-12-29T16:03:34+01:00

Alan,

I run this script using

Code:: sudo python filename.py

I have successfully run this code once:

Code:: import time from PyMata.pymata import PyMata import RPi.GPIO as GPIO # Set co-op pins BOARD_LED = 13 POTENTIOMETER = 0 # Creat a PyMata instance using the Arduino COM Port as the input parameter SERIAL_PORT = "/dev/ttyS0" firmata = PyMata( SERIAL_PORT, max_wait_time=5 ) # set digital pin 13 to be an output port firmata.set_pin_mode(BOARD_LED, firmata.OUTPUT, firmata.DIGITAL) firmata.set_pin_mode(POTENTIOMETER, firmata.INPUT, firmata.ANALOG) sensorvalue = firmata.analog_read(POTENTIOMETER) #Set GPIO pins GPIO.setmode(GPIO.BOARD) GPIO.setup(8,GPIO.OUT) #read anologue input print "Blinking LED 13 10 times" print firmata.analog_read(POTENTIOMETER) print sensorvalue #if sensorvalue<500: # for i in range(0,10): # print '< 500' # print "iteration " + str(i+1) # GPIO.output(8,True) # print 'high' # time.sleep(0.05) # GPIO.output(8,False) # print 'low' # time.sleep(0.05) # blink for 50 times for x in range(20): print x+1 print firmata.analog_read(POTENTIOMETER) firmata.digital_write(BOARD_LED, 1) # wait a half second between toggles. time.sleep(.5) firmata.digital_write(BOARD_LED, 0) time.sleep(.5) # close PyMata when we are done GPIO.cleanup() firmata.close()

But if I try to do it a second time I get the following error code

Code:: Opening Arduino Serial port /dev/ttyS0 Please wait while Arduino is being detected. This can take up to 5 seconds ... Error: Caught exception in command handler - pop from an empty deque Board Auto Discovery Failed! Traceback (most recent call last): File "pymata_anologue.py", line 13, in firmata = PyMata( SERIAL_PORT, max_wait_time=5 ) File "/usr/local/lib/python2.7/dist-packages/PyMata/pymata.py", line 148, in __init__ raise Exception( "Unable to connect to Firmata" ) Exception: Unable to connect to Firmata

Hope this is helpful.

Statistics: Posted by Maximus789 — Mon Dec 29, 2014 4:03 pm

Re: Unable to connect to Firmata

2014-12-29T15:46:06+01:00

Hi there,

Do you get an error message? You need super user privileges in order to use the GPIO pins. So you'll need to run the program using sudo. If you're already using sudo then there may be a clash somewhere in the PyMata library. I'll have a look to see if I can see anything.

Regards

Alan

Statistics: Posted by Alan — Mon Dec 29, 2014 3:46 pm

Re: Unable to connect to Firmata

2014-12-29T15:27:17+01:00

Afternoon,

This is the code that I have been trying to get to work. It seems to work a few times as it is, but wont work at all if I remove the # before the GPIO lines.

Code:: import time from PyMata.pymata import PyMata #import RPi.GPIO as GPIO #Set GPIO pins #GPIO.setmode(GPIO.BOARD) #GPIO.setup(8,GPIO.OUT) # Set co-op pins BOARD_LED = 13 POTENTIOMETER = 0 # Creat a PyMata instance using the Arduino COM Port as the input parameter SERIAL_PORT = "/dev/ttyS0" firmata = PyMata( SERIAL_PORT, max_wait_time=5 ) # set digital pin 13 to be an output port firmata.set_pin_mode(BOARD_LED, firmata.OUTPUT, firmata.DIGITAL) firmata.set_pin_mode(POTENTIOMETER, firmata.INPUT, firmata.ANALOG) sensorvalue = firmata.analog_read(POTENTIOMETER) #read anologue input print "Blinking LED 13 10 times" print firmata.analog_read(POTENTIOMETER) #if sensorvalue<500: # for i in range(0,10): # print '< 500' # print "iteration " + str(i+1) # GPIO.output(8,True) # print 'high' # time.sleep(0.05) # GPIO.output(8,False) # print 'low' # time.sleep(0.05) # blink for 50 times for x in range(50): print x+1 print firmata.analog_read(POTENTIOMETER) firmata.digital_write(BOARD_LED, 1) # wait a half second between toggles. time.sleep(.5) firmata.digital_write(BOARD_LED, 0) time.sleep(.5) # close PyMata when we are done firmata.close()

Perhaps I have made an error trying to initialize the GPIO pins?

Statistics: Posted by Maximus789 — Mon Dec 29, 2014 3:27 pm

Re: Unable to connect to Firmata

2014-12-29T13:24:48+01:00

Hi Max,

If you could post the code so that I could have a look, then that would be very helpful.

I have occasionally seen connection problems with the Pi Co-op which I believe may be due to timing issues when the Pi resets the Pi Co-op or perhaps it's due to problems with the serial communication. The problem is that I've only seen the problem very infrequently, it's tough to get a repeatable test case and rebooting does seem to solve the problem. If you've got a program which encounters the problem repeatedly then it could be very useful for resolving it.

Alternatively, the other thing that could be going wrong is that your program may not have exited cleanly one of the previous previous times it ran. This would mean that it might still be sitting there, interfering with any serial communication you later try to do with the Pi Co-op.

You can check for this by running

Code:: ps aux | grep python

which should show you all of the Python scripts running on your computer. You can kill them to shut them down completely by running

Code:: sudo kill -9 PID

where PID is the ID of programs process (number displayed in the 2nd column when you run the ps command).

Hope that helps.

Regards

Alan

Statistics: Posted by Alan — Mon Dec 29, 2014 1:24 pm

Re: Unable to connect to Firmata

2014-12-29T11:22:08+01:00

Alan,

I have managed to get an potentiometer reading (analogue) to print onto python. However this usually works twice before getting the code:
Exception: Unable to connect to Firmata

I have rebooted the pi and sometimes it works, but majority of the time it doesn't.

I can paste my code here if you want, but not convinced there is an issue with my code as it has worked in the past.

Any assistance will be appreciated.

Max

Statistics: Posted by Maximus789 — Mon Dec 29, 2014 11:22 am

Re: Unable to connect to Firmata

2014-06-23T12:21:44+01:00

Hi Arnold,

Glad you got it to work, although it's odd that it didn't work in the first place. The sequence should be that behind the scenes, a program called avrdude is started to program the Pi Co-op, and as part of this a small Python script resets the Pi Co-op ready for the program download to start. This slightly convoluted process is needed because the UART on the GPIO pins doesn't have a hardware reset line.

I'm thinking now that there could perhaps be a timing issue with the reset signal being sent out, which I'll look into in case I need to make a software fix.

Also, good point about the image, I'll add a link to the Pi Co-op product page.

Regards

Alan

Statistics: Posted by Alan — Mon Jun 23, 2014 12:21 pm

Re: Unable to connect to Firmata

2014-06-23T11:35:25+01:00

Hi,

1) Pressing the reset button did not turn the green led on.
2) The green led never flashes,

I downloaded the image and it worked. Then, I booted up with an SD card that had previously failed. Without making any changes to the card, the IDE and PyMata Blinks worked. I did not reseat the Pi Co-op or anything. Perplexing.

Thanks for your response,

Just a note: I originally looked for an image I could try; but, I couldn't find a link to it.

Arnold

Statistics: Posted by arnoldbail — Mon Jun 23, 2014 11:35 am

Re: Unable to connect to Firmata

2014-06-21T11:45:53+01:00

Hi Arnold,

Welcome to the forum. Sorry to hear you're having problems with your Pi Co-op, and also, sorry for the delay in replying to you.

Could you try a couple of things for me please?

[*] With the Pi powered on, can you press the white reset button on the Pi Co-op please? Do you see the green LED on the Pi Co-op flash?
[*] Likewise, when you try to program the Pi Co-op from the Arduino IDE or with Pymata, does the LED flash then.
[*] If possible, could you try to download our SD card image and flash it to an SD card please? This has the Arduino environment and all required programs installed, so it'd be interesting to see if you have the same problems with that.

Regards

Alan

Statistics: Posted by Alan — Sat Jun 21, 2014 11:45 am

Unable to connect to Firmata

2014-06-20T11:49:20+01:00

Hi,

I installed the Pi Co-op as per the simple install instructions. I'm also new to the Arduino. I have the latest Raspian. When I execute the Blink sketch I get a "program not responding" error. When installing Pymata, I get a:
"Please wait while Arduino is being detected. This can take up to 5 seconds ...
Board Auto Discovery Failed!"

At the end I get:

" File "/home/pi/PyMata/PyMata/pymata.py", line 148, in __init__
raise Exception( "Unable to connect to Firmata" )
Exception: Unable to connect to Firmata"

Statistics: Posted by arnoldbail — Fri Jun 20, 2014 11:49 am