Hi @samgozman
Did you get to solve your problem?
I have the same problem with a ESP32
--- Available filters and text transformations: colorize, debug, default, direct, esp32_exception_decoder, hexlify, log2file, nocontrol, printable, send_on_enter, time
--- More details at http://bit.ly/pio-monitor-filters
could not open port '/dev/cu.SLAB_USBtoUART': [Errno 16] could not open port /dev/cu.SLAB_USBtoUART: [Errno 16] Resource busy: '/dev/cu.SLAB_USBtoUART'
The terminal process "platformio 'device', 'monitor', '--environment', 'wemosbat'" terminated with exit code: 1.
I only use Visual Code with PlatformIO, tried many suggestions: disconnect and connect USB cable, close terminals, reset Visual Code, kextunload, googled at many sites and nothing.
Suddenly, I don’t know why, I got upload the bin or open the serial monitor. But when I need to connect to serial port again, the port is busy.
Isn’t there any way to reset the serial port?
All the best