Misc

enter-bootloader

Wait for a port to appear, reset the chip into the ROM bootloader (download mode), and exit, leaving it parked for another tool. The port is polled every 50 ms, and errors from a device node that isn't ready yet are retried.

idftool -p /dev/cu.usbmodem1101 enter-bootloader
idftool -m 9c:13:9e:1b:d4:6c enter-bootloader

Needs -p, -m, or --usb-serial. With -m or --usb-serial, it waits for a port with that USB serial number to appear, so -m only works for boards on their built-in USB-Serial/JTAG port.