Serial devices usually have a very small buffer, like 16 bytes or something. Could the problem be that the device isn't consuming data as fast as you write it? Is that module supposed to block your script until there is room in the buffer, or does it just throw that exception when the buffer is full?

You might try a quick experiment to see what other cases can give you the same error. What if you write a 17-byte string once? What if you write two 9-byte strings back-to-back without waiting? What if you write 5000 bytes?

There are also flow-control lines on the serial connection, so the device can indicate when it is ready to read or not. Do you have a breakout-box showing you those signals on LEDs? What happens if you write data on the line when the device isn't ClearToSend?

Ah, and I just learned something. (from that StackOverflow post)

RTS/CTS wasn't supposed to ever be a flow control mechanism, originally; it was for half-duplex modems to coordinate who was sending and who was receiving. RTS and CTS got misused for flow control so often that it became standard.

In reply to Re^4: Win32::SerialPort, buffer overflow by NERDVANA
in thread Win32::SerialPort, buffer overflow by jmClifford

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