# Writing to a serial device failing mysteriously

I have a device which communicates with the computer through serial. The device waits until it receives the character 'a', and then begins to stream data. I have been able to connect to the device and test it in PuTTY, where hitting 'a' will begin the stream and I can read the data just fine in terminal.

Now I would like to work with this data in Mathematica. Working in a notebook, it looks like I can properly open the device. However, attempting to write to it gives me a rather cryptic error--especially when I know this works in PuTTY.

If anyone can help me to make sense of this, that would be fantastic.

    dev = DeviceOpen["Serial", "\\.\\COM11"];