Stomper Building Guide

Break the PCB apart and clean the edges with a file or snips.

Even though the PCBs are electrically tested during manufacturing and visually inspected before being mailed, inspect the PCB for breaks in traces.

PCB showing optional areas and TEST POINTS.

BOM:

6 100nF Ceramic Disc Capacitors
2 10uF Electrolytic Capacitors
2 100uF Electrolytic Capacitors
2 1uF Polyester Capacitor
2 20pF Ceramic Disc Capacitors
1 100R Resistor
9 1K Resistors
2 2K Resistor
5 10K Resistors
ATMEGA328P-PU DIL Microcontroller
TL071P Opamp DIL08
2N3904 NPN Transistor
7805L TO92 5v 100ma Power Regulator
2 1n4007 Diodes
16 1n5817 Schottky Diodes
5 10kB Potentiometer 9mm vertical PCB mount
5mm LED
16MHz crystal
5×2 Header (Eurorack Power)
(optional) 1×4 Header (Programming)
8 3.5mm “Thonkiconn”-style sockets with pin legs. Regular Kobiconn sockets with lugs can be used with the modifications described below.
DIL28-3 Socket
DIL08 Socket
8HP Panel
2 1×4 Male Headers
2 1×4 Female Headers
1 1×8 Male Header
1 1×8 Female Header
1 1×3 Male Header
1 2-Position Pin Header Jumper

 

1. Begin with the resistors and diodes. Take care to ensure that the diodes are oriented properly. Double-check before soldering – this is the biggest cause of problems.

All unlabelled diodes are 1n5817 Schottkys. Most of these components mount flush against the board.

If you don’t have a 2k resistor, a 1.8k or 2.2k is okay. None of the resistor values are critical.

2. Next add capacitors. Make sure the electrolytics are oriented properly.

3. Add the IC sockets. Again, check the orientation. The notch should match the silk screened notch.

4. Now add the power regulator, crystal, and transistor, double check the orientation before soldering. Don’t spend too long soldering these – three seconds maximum per lead. It’s a good idea to put an alligator clip under the TO92 bodies to act as a heat sink while soldering.

5. Add the potentiometers, LED, and 3.5mm sockets. Don’t forget to clip the alignment tab from the face of the pots.
It’s easier to hold the sockets and LED in place by mounting the panel to the center pot.

MAP_6323_lzn
The 3.5mm sockets and LED can be held in place for easier soldering with the panel temporarily mounted to the center potentiometer.
MAP_6327_lzn
Panel mount sockets can be used by trimming the legs to fit in the hole, and soldering a resistor-leg wire to the ground lead.

MAP_6328_lzn

6. Now is a good time to check all the joints to make sure there’s no shorts or badly-soldered connections.

With a multimeter check for shorts between ground and +12 and -12. on the power connector. There’s three oblong pads behind the power connector to make this easy. If you find a short then stop and double-check your soldering.

7. Add the remaining headers to the PCBs. Take a close look at the following diagram to see how the panels are attached together. It doesn’t matter if the male or female goes on the top or bottom board as long as they mate properly.

MAP_6333_lzn
MAP_6332_lzn

MAP_6330_lznMAP_6331_lzn

8. Mount the boards to the panel and tighten all nuts.

9. Done! Time to test.

Check that power isn’t shorted as in step 6.

If that’s okay then connect power with a finger on the POWER REGULATOR. If the regulator gets warm or hot quickly then disconnect the power and check your connections and soldering.

If it’s okay, then test the voltage at the test points (shown above) with a multimeter. It’s okay if 5V by a couple tenths of a volt. +12 and -12 could be up to +5V overvoltage depending on the power supply and load, but that’s okay.

10. If everything checks out, unpower the board and populate with the opamp and microcontroller ICs. Double check the orientation.

The microcontroller should already be programmed. If you’re using a microcontroller supplied by us then it’s ready to go.

If using your own then you should flash the bootloader and software now. The bootloader can’t be flashed through the FTDI port.
Latest version of the STOMPER firmware and instructions for flashing is here: http://github.com/THX2112/stomper.

Power the board while watching the front panel. The LED should flash once briefly as soon as power is applied. If it does, yeah!

If not, turn off the power immediately and double check wiring and connections. See if any pins got bent while inserting into the socket. Is the LED wired properly?

MAP_6335_lznMAP_6243_lzn

 

Updating Firmware

The Stomper firmware is updated through the FTDI port with a USB Arduino Adapter.

Connect DTR to CTS, RX to TX, TX to RX, and GND to GND.

Download the latest firmware from here: http://github.com/THX2112/stomper and put it into your Arduino sketch directory.

Load it with the Arduino IDE. Set Tools>Board to “Arduino Uno”, and Tools>Serial Port to the port the USB FTDI interface is using (the Arduino IDE usually figures this out for itself.)

Click the “Upload” button and it should compile and transfer.

Troubleshooting

 

  • No power shorts to ground?
  • Are all the components oriented properly?
  • All connections soldered properly?
  • No solder bridges between joints?
  • All wires going to the right places?

 

If still having problems send an email to [email protected]. Also try the DIY forum at muffwiggler.com.

 

Hacking

Several unused ports have been broken out:

D2: Digital input or output.

D5: Supports PWM. Digital input or output.

D6: Supports PWM. Digital input or output.

D10: Supports PWM. Digital input or output.

D11: Supports PWM. Digital input or output.

D12: Supports PWM. Digital input or output.

D13: Supports PWM. Digital input or output.

A5: Analog Input (ADC). 10-bit. Protected.

And of course the existing I/Os can be reassigned and the pots/sockets rewired.

It should also work on +/-15V systems as-is, but hasn’t been tested. All of the inputs and outputs are heavily protected and should easily handle triggers and CV inputs of up to +/-20V and more.