Add troubleshooting guide

Author: coderkevin

TROUBLESHOOTING.md

@@ -0,0 +1,82 @@
+# Mini NES Troubleshooting Guide
+
+Things not working the way they should? Check here for some tactics on diagnosing your problem.
+
+## Power Buttons
+
+### Software
+
+- Program: `nes_buttons` daemon (should be running on system startup)
+- How to start: `sudo systemctl start nes_buttons`
+- How to stop: `sudo systemctl stop nes_buttons`
+- How to check the log: `cat /dev/shm/nes_buttons.log`
+
+If the system daemon isn't behaving the way you'd expect, you can run the code manually.
+
+1. `sudo systemctl stop nes_buttons`
+2. Change your directory to the `buttons` subdirectory of the source.
+3. `python nes_buttons.py`
+4. Logging output should be visible on the command line. (If you see a "RuntimeWarning" about a channel already in use, that's okay.)
+5. Press the reset button. You should see logging output about restarting.
+
+### Electrical
+
+If your power isn't shuttting down and starting back up correctly, here are a couple things to check:
+
+1. Ensure the power button is unlatched and then plug in the RPi power.
+2. Use a multimeter to test for voltage on RUN pin #1. It should be around 0.5v or less.
+3. Press the power button to latch it.
+4. The LED should turn on, indicating that RUN pin #1 has risen in voltage.
+5. The system should power up as normal.
+
+If your RPi turns off but not back on, it's likely because the RUN pin isn't pulled low enough before rising back to 3.3v. On my RPi 3, a 10k is enough to drop the RUN pin to 0.5v. Check with a multimeter when the device is plugged in, but the power button is not on. If it's too high, then try a lower value resistor. Something between 10k down to 1k should work. When you try out a different resistor, test the voltage, then try the behavior.
+
+
+## NFC Reader
+
+### Software
+
+- Program: `nfc_poll` daemon (should be running on system startup)
+- How to start: `sudo systemctl start nfc_poll`
+- How to stop: `sudo systemctl stop nfc_poll`
+- How to check the log: `cat /dev/shm/nfc_poll.log`
+
+If the system daemon isn't behaving the way you'd expect, you can run the code manually.
+
+1. `sudo systemctl stop nfc_poll`
+2. Change your directory to the `nfc` subdirectory of the source.
+3. `python nfc_poll.py`
+4. Logging output should be visible on the command line.
+5. Try placing a cartridge over the sensor and watch for output.
+
+### Electrical
+
+If your nfc reader isn't working correctly, it should show up in the logs. If you suspect it's electrical, here are some things to check:
+
+1. There are two small DIP switches on the NFC board to select the mode. Ensure they're set correctly for i2c.
+2. Ensure the correct pins are connected to the RPi header and the NFC board. Revisit the wiring diagram for this.
+3. The red LED on the NFC board should be on any time the RPi header is plugged in.
+
+
+## Screen Manager
+
+### Software
+
+- Script: `/var/lib/screen_manager/screen_manager.py` (called by autostart.sh)
+- How to check the log: `cat /dev/shm/screen_manager.log`
+
+This script should be fairly stable and shouldn't have too many problems. If emulationstation is running on startup, then this script is running.
+
+The installation for this script modifies `/opt/retropie/configs/all/autostart.sh`. It comments out emulationstation and adds `python screen_manager.py` instead. If this is causing problems, you can edit this file and restore default operation there.
+
+You can run this script manually just like the others, but you'll want to disable it in `autostart.sh` before you do.
+
+To test:
+
+1. Edit the config file at `cat /dev/shm/screen_manager.cfg` in accordance with [the screen readme](https://github.com/coderkevin/mini-nes/blob/master/screen/README.md)
+2. Try a `dashboard` action.
+3. Try a `rom` action.
+4. Try deleting the file to ensure the default dashboard action runs.
+
+
+