COM port won't read - Toit on Windows desktop

[milkmansson]

Using the following on Windows, attempting to run on the desktop directly:

import uart

DEVICE := "COM12"
BAUD   := 9600

main:
  uart := uart.Port DEVICE --baud-rate=BAUD
  print "Started..."
  reader := uart.in
  while true:
    print reader.processed
    print reader.read.to-string
    sleep --ms=10

... results in no data, and the code blocking on print reader.read.to-string.

• Testing using a known good 9600 source, which connects OK with putty using the same device string.
• Connecting first with putty, not closing, and trying to run this on toit results in EXCEPTION error. PERMISSION_DENIED (as expected).
• Connecting first with toit, leaving it blocking, and then trying to open with putty results in 'access denied' (as expected).
• Tried using admin elevated powershell on windows, no dice.
• Tried exact code in a linux VM on the same windows install: works perfectly with no hardware change (except change DEVICE := "/dev/ttyUSB0")

I have a Mac at my disposal somewhere, I'll give that a go if you need.