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Issue Possible Cause Try
Cannot connect via WiFi pi-Stomp is out of range Move pi-Stomp closer to WiFi router, or computer if in Hotspot mode. Reboot by cycling the power.
Cannot connect via WiFi Raspberry Pi is not booting Make sure Red LED on pi is lit. If not, check power. Is SD card properly etched and mounted?
Cannot connect via WiFi Patchbox wifi config not correct If LCD display is displaying a pedalboard, Long-Press PBoard knob until System Menu displays. Select/click System Info. Select/click Enable Hotspot. Try connecting via ssh to patchbox.local. Repeat network configuration
Original pi-Stomp (v1.x) with GFX Hat LCD not displaying anything (minutes after booting) LCD not connected correctly python3 ~/Pimoroni/gfxhat/examples/ (if “Hello World” is displayed, the hardware is probably fine. If it's not, make sure the pi and LCD are fully seated into their headers. May also warrant checking the header soldering for pins 1, 2, 3, 9, 19, 23, 24, 29, 31)
Color LCD is lit but all white or stuck on pi-Stomp logo Error encountered by mod-ala-pi-stomp service ssh to the pi-Stomp. Run sudo journalctl -fu mod-ala-pi-stomp to see the log for the service and hopefully discover the error. If nothing is obvious, check the other dependent services: sudo journalctl -fu modep-mod-ui, sudo journalctl -fu modep-mod-host, sudo journalctl -fu jack
No audio passing when pi-Stomp is processing is enabled Incorrect routing Check cabling (eg. instrument > In1, Out1 > amp) and assure it's consistent with the routing of the current pedalboard shown in MOD webui. Make sure the path thru plugins from input to output isn't broken. Check to see if the other (eg. In2/Out2) works.
… still no audio passing Volume is down Turn Volume knob up. Make sure input gain is not too low - From the System menu, select/click Input gain, set value to 0 or greater OR run via ssh: amixer -c 0 set Capture 80%
… still no audio passing HiFi output is disabled Run the following via ssh: amixer set -c 0 'Output Mixer HiFi' on
… still no audio passing Audio services in bad state Load the pedalboard named “Default”. If still no signal passing, restart the audio (Long-Press PBoard knob to get the System menu, select/click Restart sound engine)
Audio passing but either too quiet or distorted Input gain not matched to input source Follow Audio Setup instructions. If it's still too quiet or distorted, check if the plugins on the pedalboard are responsible or choose another pedalboard, like 'Default'
No Audio from Headphone jack Headphone jack only gets processed audio Make sure the pi-Stomp is not bypassed. Control its volume via the System Settings Menu (Long-Press upper encoder)
Can't get past Hardware Test Hardware issue exists or user error (pi-Stomp v1.x) It's advisable to pay attention to which test is failing. If you just want to move on despite the issue, ssh to it and run 'touch /home/patch/pi-stomp/pistomp/.hardware_tests_passed'. If you'd like to run the tests again: 'rm /home/patch/pi-stomp/pistomp/.hardware_tests_passed; ps-restart'
Audio Glitching Overworked CPU In the Web UI, see if the CPU meter is going above 75% or many XRUNS are logged (more than 100). If so, try switching to 256 Frames (click on control next to XRUNS), or removing plugins from your pedalboard. CPU intensive plugins like generators, pitch shift and some distortions are the usual hogs.
… still glitching Unnecessary processes/services running If you've installed additional software, those processes might be hogging the CPU. Try shutting them down, see tips below.

Hardware Debug Utility

A very clever pi-Stomp user added an awesome utility for verifying that attached hardware is working correctly.

From an ssh session:

ps-run --host test

This brings up a curses UI in the terminal.

From here you can toggle footswithes, tweak knobs and the encoder. If you see the corresponding change in the UI, the control is probably working. The Capture volume and Headphone volume only work if using the AudioInjector sound card.

To return to normal operation:


No Processed Audio

If you've done the above and still don't hear audio being processed, it might be time to check the input circuitry.

First make sure processing is enabled and not bypassed. The “power” icon at the top left of the LCD should be green. If it's grey, make it green by navigating to it, then clicking the encoder.

“Signal Tracing” is a common technique for debugging audio issues. Essentially, we'll be using the cable going to your amp as a signal sniffer. You can use a pair of alligator jumper cables connected like this.

The instrument is plugged into the input jack. The cable going to the amp is grounded (green jumper). And the amp cable tip becomes a signal probe by connecting it (yellow jumper) to a short stub of non-stranded wire . When the wire stub is touching a component/pad with a live signal, you should hear the instrument coming thru the amp. If you don't hear it, a component or circuit board trace before that point is the likely culprit.

Below are the points to probe (numbers in fuchsia font). The text in [] suggests the components and circuit board traces to check if you Don't detect signal at that point.

  1. Input Jack
  2. Via [Check solder pad of Jin jack and trace to via]
  3. R1 [Relay could be malfunctioning or in bypass mode. C1 may be bad. Bad solder joints on Rly, C1 or R1]
  4. R2 [Trace or bad solder between R1 and R2]
  5. U3 pin3 [Trace or bad solder between R2 and U3]
  6. U3 pin2 [U3 chip is misoriented/badly seated in socket; U3 is fried or not powered correctly - check voltage between pins 4 and 8 (yellow dots) is around 3.0 volts]
  7. Hin Left [Bad solder of S3 socket, Hin Header or trace between them]

General Hardware Troubleshooting

The dmesg command shows kernel logs which may contain useful information when debugging hardware failures.

dmesg | less 

enter ‘q’ to exit.

General Software Debugging


Most all of the software important for pi-Stomp to run correctly are linux services. Some of the most relevant services:

amidiauto.service - the automatic MIDI interconnection service.

jack.service - the Jack backend service. If it has failed or its logs are indicating errors, you will not hear any audio. Try reconfiguring Jack to use a different audio card or larger buffers using sudo patchbox-config, going to ‘jack’ section.

modep-mod-host.service - the LV2 plugin host which uses jack to process audio

modep-mod-ui.service - the service which serves the MOD webui for configuring pedalboards

mod-ala-pi-stomp.service - pi-stomp software/firmware which monitors all input devices, drives the LCD and interacts with modep-mod-host and modep-mod-ui.

touchosc2midi.service - the TouchOSC2MIDI bridge service. If it is not running, TouchOSC Apps will not work.

wifi-hotspot.service - this service is used to control whether Patchbox OS behaves as a WiFi hotspot and it is used to set the desired behavior.

systemctl & journalctl

The systemctl command is used to control services. The journalctl command is used to view the log output of services. Below are some common uses.

Command usage

systemctl --help
journalctl --help

Status listing of all services

sudo systemctl status

List services which failed to run:

sudo systemctl list-units --failed

Restart a service

sudo systemctl restart <SERVICE-NAME>

Stop a service

sudo systemctl stop <SERVICE-NAME>

Show a running log of all services

sudo journalctl -f  

Show a running log of a specific service

sudo journalctl -f -u <SERVICE-NAME>

Search the log for errors

sudo journalctl | grep 'error'
troubleshooting_guide.txt · Last modified: 2022/03/20 20:29 by admin