title: Connecting OPP to your computer
Archived 2026-09-13 from
https://github.com/missionpinball/mpf-docs/blob/main/docs/hardware/opp/connecting.md. Full raw
markdown, as returned by the source fetch.
Connect the OPP board to your computer via USB. Make sure OPP chains don't get too long since
serial throughput is limited per chain. You can connect multiple chains.
mpf hardware scan lists connected node boards:
$ mpf hardware scan
Connected CPUs:
- Port: com1 at 115200 baud
-> Board: 0x20 Firmware: 0x10100
-> Board: 0x21 Firmware: 0x10100
Incand cards:
- CPU: com1 Board: 0x20 Card: 0 Numbers: [16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31]
Input cards:
- CPU: com1 Board: 0x20 Card: 0 Numbers: [0, 1, 2, 3, 8, 9, 10, 11, 12, 13, 14, 15]
- CPU: com1 Board: 0x21 Card: 1 Numbers: [0, 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27]
Solenoid cards:
- CPU: com1 Board: 0x20 Card: 0 Numbers: [0, 1, 2, 3]
- CPU: com1 Board: 0x21 Card: 1 Numbers: [12, 13, 14, 15]
LEDs:
- CPU: com1 Board: 0x21 Card: 1
If boards don't show up, see the OPP troubleshooting guide (mpf-docs-opp-troubleshooting in
this archive).
The Cypress thermometer module conflicts with OPP. In /etc/modprobe.d/blacklist.conf:
blacklist cytherm
Create the file as root if it doesn't exist, then reboot.
With more than one ttyACM device, assign stable names based on USB port. Find the port's
DEVPATH via udevadm info /dev/ttyACM0, then add a rule in /etc/udev/rules.d/opp.rules:
SUBSYSTEM=="tty", ACTION=="add", DEVPATH=="/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.1/*", SYMLINK+="ttyOPP1", GROUP="adm", MODE="0660"
After reboot, that USB port yields /dev/ttyOPP1.
ModemManager tries to initialize /dev/ttyACMxx devices as modems, causing delays/garbage on
the bus. If you don't use modems:
sudo systemctl disable ModemManager
sudo systemctl stop ModemManager
See the OPP troubleshooting guide (mpf-docs-opp-troubleshooting in this archive).