Invalid board number error while outputting voltages 2nd time

[Sid_1]

Hi there, I am using the Python library mcculw on a Windows 10 mcahine. I am using the USB 231 DAQ.

When I send voltages for the first time (using a_out_scan() method) everything works fine. When I send it for the second time, I get this error:

daq_device_info.py, line 37, in __init__
    raise ULError(ErrorCode.BADBOARD)
mcculw.ul.ULError: Error ErrorCode.BADBOARD: Invalid board number.

Notes:

1. I have stored the board number in a variable board_num=0. I am not changing it at all during program execution. So, I don't know how it changes and how I get the error.
2. I initialize the device using the following code each time I try to send voltage. The following is an excerpt from my code:

   class DaqLogic:
       '''
       This class has various methods to interact with the DAQ
       '''
       def __init__(self):
           self.board_num = 0
           self.daq_info = DaqDeviceInfo(self.board_num)
           self.ao_info = self.daq_info.get_ao_info()
   
           #Useful constants for the DAQ
           self.low_chan = 0
           self.high_chan = 1
           self.num_chans = self.high_chan - self.low_chan + 1
           self.ao_range = ULRange.BIP10VOLTS
           self.use_device_detection = True
           self.dev_id_list = []
           self.calibrationFactor = 1
           self.lcdFreq = 200 # in Hz
   
       def configure_first_detected_device(self):
           '''
           Configures the first detected device. Ingores Instacl config.
           '''
           ul.ignore_instacal()
           devices = ul.get_daq_device_inventory(InterfaceType.ANY)
           if not devices:
               raise Exception('Error: No DAQ devices found')
   
           print('Found', len(devices), 'DAQ device(s):')
           for device in devices:
               print('  ', device.product_name, ' (', device.unique_id, ') - ',
                   'Device ID = ', device.product_id, sep='')
   
           # Add the first DAQ device to the UL with the specified board number
           ul.create_daq_device(self.board_num, devices[0])
   
       def intialize_daq(self):
           '''
           Initializes the DAQ
           '''
           try:
               self.configure_first_detected_device()
               daq_dev_info = DaqDeviceInfo(self.board_num)
               if not daq_dev_info.supports_analog_output:
                   raise Exception('Error: The DAQ device does not support '
                                   'analog output')
           except ULError as e:
               # Todo: Create alert window
               print("Error: ", e)

    

Is it that I should not initialize the device each time I wish to send voltage ?
I guess, I must initialize only once and then store some reference to the device for further use, like sending voltages for 2nd time.

Edited October 10, 2022 by Sid_1

[Jeffrey]

Hello @Sid_1

Correct. You only need to initialize the device (once) at the start of your app.

and don't release the device until you are exiting your app.

Once it is initialized you don't need to re-initialize unless you end the app.

Regards,

Jeffrey

[Sid_1]

Hello Jeffery. Thanks a lot for the solution. Thanks for the fast reply.

I would just like to restate the solution for anyone reading this page:

Don't use ul.release_daq_device(board_num) if you are planning to send more voltages.

Edited October 11, 2022 by Sid_1