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robve · (This post was last modified: 02-16-2023 08:29 PM by robve.)

Update

Further down the rabbit hole...

It seemed crazy to me why the FTDI driver didn't respect the CTS input from the PC-G850 on my MacOS M1 machine as I stated in the checklist. I tested with an Adafruit FTDI Friend and a FTDI USB cable from the FTDI manufacturer. The problem is a bug in the latest FTDI CP210x/VCP driver 1.5.0 for MacOS 12, because testing on Windows with RealTerm shows that the CTS input levels are correct and in fact respected when sending to the PC-G850, as shown in the images below.

CTS is low when PC-G850 not ready to receive and sending to the PC-850 is indeed blocked:

[Image: RT-1.PNG]

CTS is high when the PC-G850 ready to receive, e.g. TEXT Sio Load:

[Image: RT-2.PNG]

Strange behavior with the FTDI 5V adapter however remains, even on Windows, whereas the FTDI 3.3V adapter is fine. It is not possible to send from the PC-G850 to the PC with the FTDI 5V adapter when DTR is set. It should be cleared first manually, before the PC accepts data from the PC-G850:

[Image: RT-3.PNG]

For this reason to fiddle with DTR, it's not practical to use FTDI 5V, but I can't put my finger on the reason why this is any different from the FTDI 3.3V behavior that works fine.

To conclude, the FTDI driver for a Windows machine and Mac Intel machine work. However, the FTDI driver 1.5.0 for MacOS fails to respect FTDI CTS input on a Mac M1. This is totally unexpected and not acceptable!

- Rob