Description
Tried to communicate to a serial device using the MCP2200 converter. It works well if there are only 2 USB devices in total. If both keyboard and mouse are plugged in it gives error but works perfectly is only one of them are present.
The problem can be tested using an MCP2200 breakout board, like
http://dangerousprototypes.com…..b-built-6/
by shorting the Rx and Tx pins, and running the following program.
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import serial, time
fd = serial.Serial('/dev/ttyACM0', 38400, stopbits=1,
timeout = 1.0, parity=serial.PARITY_EVEN)
fd.flush()
for k in range(256):
fd.write(chr(k))
time.sleep(0.01) #some delay
res = fd.read()
if ord(res) != k:
print 'ERROR ', k, ord(res)
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The kernel error massage is:
Apr 17 14:52:11 raspberrypi kernel:
Apr 17 14:52:11 raspberrypi kernel: INFO:: periodic_channel_available: Total channels: 8, Periodic: 6, Non-periodic: 2
Apr 17 14:52:11 raspberrypi kernel:
Apr 17 14:52:11 raspberrypi kernel: INFO:: schedule_periodic: No host channel available for periodic transfer.
Apr 17 14:52:11 raspberrypi kernel:
Apr 17 14:52:11 raspberrypi kernel: ERROR::dwc_otg_hcd_urb_enqueue:487: DWC OTG HCD URB Enqueue failed adding QTD. Error status -4008
Ajith