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Troubleshooting P-Roc/P3-Roc

If you got problems with your hardware platform we first recommend to read our troubleshooting guide. Here are some hardware platform specific steps:

P/P3-Roc Does Not Show Up In Device Manager or dmesg Log

If your P/P3-Roc does not show up in device manager (Windows) or does not create a line in dmesg or lsusb (Linux/Mac) have a look at the USB cable and connection. Bad cables are a thing (especially for longer cables). Try removing USB hubs.

Is the board powered up? Are the four blue LEDs circling? If not check your power supply.

ImportError in MPF Log

If you see something along this in your log:

in <module>
   from mpf.platform.pinproc.x86.python36 import pinproc

ImportError: DLL load failed: The specified module could not be found

This usually means that the FTDI libs are not installed in the correct version. On Linux pinproc might not be installed at all. On Windows Visual C++ Redistributable for Visual Studio might also be missing in the correct version. Have a look a the install instructions for your OS to find and install the correct requirements.

Failed to reset P/P3-Roc

If you see this repeatedly in the log of MPF:

Failed to reset P/P3-Roc: OSError: Error in WriteData: wrote 0 of 8 bytes. Is your P/P3-Roc connected and powered up?
Will retry creating PinPROC and resetting it in 1s.

This usually means that the P/P3-Roc is either not powered up or not connected.

Random Crashes of MPF

You might see errors such as the following (usually in

OSError: Error in WriteData: wrote 0 of 8 bytes

This error is triggered by communication issues with the P/P3-Roc. Often this is caused by an unreliable power supply or overload on the 5V rail of that supply. This might also be caused by a bad USB cable. In any case you should also find USB communication errors in your operating system which might give you further clues.

Run Hardware Scan

Using mpf hardware scan you can find out if your P/P3-Roc is talking properly to MPF using USB. Additionally, it will show you which SW-16 are connected:

$ mpf hardware scan

Firmware Version: 2 Firmware Revision: 6 Hardware Board ID: 1
SW-16 boards found:
 - Board: 0 Switches: 16 Device Type: A3 Board ID: 0
 - Board: 1 Switches: 16 Device Type: A3 Board ID: 1
 - Board: 2 Switches: 16 Device Type: A4 Board ID: 2

Unfortunately, MPF cannot know which PD-16 or PD-LED are connected as this information is not available. See firmware_upgrade for details.

Enable Debugging

If you got problems with your platform try to enable debug first. As described in the general debugging section of our troubleshooting guide this is done by adding debug: true to your p_roc config section:

  debug: true

This will add a lot more debugging and might slow down MPF a bit. We recommend to disable/remove it after finishing debugging.

Enable Bus Tracing

If your hardware behaves different from the way you told it to in MPF or if you are seeing lags or delays it might be wise to turn on bus tracing.

  debug: true
  trace_bus: true

This logs all calls to libpinproc. This will cause a lot of additional log lines and might considerably slow down MPF. Definitely disable this after you finished debugging.

Upgrade the Firmware of Your P/P3-Roc

If you experience problems around hardware rules or such consider upgrading your P/P3-Roc firmware. Sometimes bugs in the firmware get fixed or stuff becomes more robust. For some known cases MPF will crash intentionally and tell you to upgrade but there might be cases which we do not know.

See How to update the Firmware of the P-Roc or P3-Roc for details about firmware upgrades.

Switches Are Not Registering

If your coils are working but switches are not registering please check the following points:

On the P-Roc

  • Is 12V power available? This will disable switches but not much else.
  • Is ground connected properly to your switches?

On the P3-Roc

  • Do your SW-16 show in mpf hardware scan? (see above)
  • If not: Is the SW-16 bus connected properly (and not twisted)?
  • Is ground connected properly to your switches? Should be connected to pin 10 on J2 or J6 of SW-16.

Some Drivers Are Not Working

If some drivers are working but other are not.

On the P-Roc

If you see the following message on your console (not log; you might have to use the -t commandline flag to see them):

Refusing to update driver #144; polarity differs on non-custom machine.

This means that the polarity which is defined for your machine type (i.e. WPC) does not match your driver definition. If you see this please tell us in the MPF user forum and we will investigate this with you.

All Coils Turn On When I Power Up My Machine

If this happens and MPF is not yet running you likely do not have common ground between high voltage and logic power. Turn your machine off and only turn it back on when you have fixed and verified common ground. Read the section about common ground for details or consult an electrical engineer.

If this happens shortly after MPF started and you are using a P-Roc this might have to do with the polarity of your coils. Check the polarity setting and make sure you configured the correct machine type as there are different defaults in different machine types.

In any case we recommend that you test this with either less voltage (i.e. 12V instead of 48V) or by using lamps instead of coils on your outputs as that will prevent hardware damage due to overcurrent.

Serial Bus Issues

Bad Cables/Interference

Each serial bus connector has a + and a - pin. The serial cables connect from board to board like jumper-cables + to + and - to -. Connecting ground pins on the serial bus is not required. A bad serial cable can be difficult to diagnose, particularly if it is the first serial cable in a chain as it will prevent signals to all boards downstream of the bad connection. One clue that a bad serial cable is present is if some of the boards function but others do not. Another clue which is sometimes present on the driver bus is discovered looking at the driver boards watchdog timer indicator. On the PD-LED the watchdog is indicated by a lit diode D3. On the PD-16 it is diode D11. The watchdog turns off when the board is receiving signal over the driver bus from the P3-ROC when MPF is running (including attract mode). If wiggling serial cables causes the watch dog to light, a loos connection or bad cable is present. While the switches bus does not have an equivelent watchdog, the game's switch status screen can be monitored while wiggling cables looking for a loose connection. It is possible for the vibration of a mechanism (notoriously from a pop bumper) to cause intermittent faults in a poorly connecting serial cable. Such intermittent faults are difficult to diagnose.


The P3-ROC interfaces to the playfield through two serial busses. The switches serial bus connects SW-16 boards through J11 and/or J14. The driver serial bus connects PD-16 and PD-LED boards through J12 and J15. The serial busses are designed to allow boards to be connected in a daisy chain fashion to each plug. A sourse of unreliable communication on the buses is improper termination. The last board on each chain (not to be confused with the board with the highest address) should have dipswitch 8 set to ON. For example is the switches serial bus has 6 boards with J11 connecting to board A B and C and J14 connecting to boards D, E and F, dipswitch 8 should be set to ON on boards C and F and set to OFF on all other SW 16 boards. (Terminating board B would prevent communication from board C on that side of the chain.) The same termination strategy also applies to driver boards. For example if a mix of PD-LED and PD-16 boards connect through J15 as A, B, C, D, and E with E being the last board, board E would have dipswitch 8 set to ON.

Additionally, the P3-ROC board itself also has termination dip switches (7 and 8) for the switches serial bus plugs. These should be set to ON. There are no termination dip switches for the driver bus on the P3-ROC board.

Correct Addressing

Each of the SW-16 boards requires a unique binary address which is set by the board's dipswitches 1 through 6. Although the P3-ROC has two serial switch connectors (J11 and J14) there is only one serial switch bus. Meaning, if one SW-16 board connects to the P3-ROC through J11 and another through J14 the SW-16 boards will still require separate addresses to be properly registered.

Similarly, the PD-16 and PD-LED driver boards also each require an unique address on the driver bus accessed through J12 and J15 on the P3-ROC. If for instance a PD-16 and a PD-LED share on the same address, commands through the driver serial bus meant to drive LEDs can acutate coils even if the boards are interfacing through different plugs.

On the SW-16, PD-16 and PD-LED boards themselves dipswitch addressing is somewhat counterintuitive. Switch one is the lowest address bit and on the SW-16 switch 6 is the highest. Reading the switch block from left (starting at switch 1) to right, binary address zero would be 000000, address one through four would be 100000, 010000, 110000 and 001000, respectively. The PD-LED sets addresses on dipswitches 1 through 5 and the PD-16 uses dipswitches 1 through 4 giving these boards fewer address possibilities than the SW-16 which uses switches 1 through 6.

Coils Are Not Firing

What to do if your coils are not working?

title: Coils Are Not Firing

Coils Are Not Firing

What to do if your coils are not working?

Check if Your Hardware is Working at all

Sounds stupid but this is a good start: Is the hardware working at all? Do you see switch hits in the logs? If not, check our section Your hardware is not working at all.

Check the Watchdog

If switches (or other features of the platform) are working but coils are not we have to dig deeper. Most hardware platforms have some kind of watchdog. Often there is some LED which indicates if the watchdog is received. The MPF log might also contain clues (especially if you have enabled debug and run MPF with verbose flags -v -V). If the watchdog is not received by your platform it will not enable coils.

In most cases watchdog related problems indicate wiring problems. Check if your boards are properly wired.

Test Your Coil Numbers using MPF Service CLI

Hardware is connected and generally working, watchdog is good but still your coils are not working? Maybe something with the numbering is odd. Lets tests that using the MPF Service CLI. Alternatively, you can also use service mode if you have already configured it. Both ways work similarly.

To use service cli:

  1. Open two consoles
  2. Start your game (e.g. using mpf both)
  3. Start the service cli from within your game folder using mpf service.
  4. Type list_coils and press ENTER to see a list of coils.
  5. Type coil_pulse your_coil and press ENTER to pulse it.

Does it work? If not check the log and try verify the coil number. If you do not specify default_pulse_ms MPF will use 10ms which might not be enough for some mechs. Try to increase that gently (maybe 20ms or 30ms).

Reducing light update rate

If you got a lot of lights you might run into bus contention issues. You can reduce the light update rate in MPF:

  default_light_hw_update_hz: 30   # defaults to 50

If you set this too low fades will be less smooth but otherwise it should not affect your game.

Your hardware is not working at all

If your hardware is not working at all make sure that you removed the options -X, -x and --vpx from your mpf both or mpf game command line. Those options will overwrite the settings in your hardware section and MPF will not even try to connect to your hardware. If you got config errors we suggest you add -X to figure things out without interfacing real hardware all the time. Just keep that option in mind.

Another stupid thing to check: Is your hardware connected to your PC? We know it is stupid but a loose USB connector has happened to most of us.

On Linux you might want to run the command lsusb which should show both of your micro controllers connected. You should see two lines similar to

Bus 002 Device 014: ID 0483:5740 STMicroelectronics Virtual COM Port
Bus 002 Device 015: ID 0483:5740 STMicroelectronics Virtual COM Port

If you are unsure about the output, run the command once with your controllers connected and once without. If there is no difference, then for sure the USB device is not properly connected.

If you got problems with some switches also add debug: true to those as it will give to more insights into the intentions of those devices. Same will work for flippers, coils, lights, servos, steppers and more. See general debugging section for details.

Run MPF with verbose flag

See general debugging section for details. TLDR: run mpf both -t -v -V.

Report Your Issue and Ask For Help

If you cannot find the issue yourself please prepare some information about your issue according to our troubleshooting guide and ask in our forum.

Consider Improving the Documentation

Did you solve your issue but found that some relevant information in the documentation is missing or should be linked/located elsewhere? Either tell us in the forum or consider improving the documentation yourself to save future users some troubles the same way others saved you some troubles by writing this documentation.

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