OpenOCD configuration for an Adafruit Trinket M0 (probably others too) connected via generic ST-Link v2 programmer

openocd-trinket.cfg

# OpenOCD configuration for the Adafruit Trinket M0
#	    https://www.adafruit.com/product/3500
# connected via a generic ST-Link/v2 compatible programmer
#	    https://amazon.com/s/?keywords=stlink%20v2

# Consult the pinout for the location of the SWCLK and SWDIO pins
# and connect the 3.3v line on the programmer to VBAT
#	    https://learn.adafruit.com/assets/49778

# It's not necessary to set the adapter speed, since OpenOCD
# figures it out, explicitly setting these speeds silences a
# few slightly annoying notices about clock rates

source [find interface/stlink-v2.cfg]
adapter_khz 950

# Magic incantation scraped off a bunch of forums
set CPUTAPID 0x0bc11477

# Trinket M0 is an ATSAMD21E18
source [find target/at91samdXX.cfg]
adapter_khz 240