Full Build Instructions for pi-Stomp Core (board version 2.0.3)

Bill of Materials for board version 2.0.3

Back to the Main pi-Stomp Core page

• Do not attempt to build this if you are not already comfortable soldering printed circuit boards. This is a rather advanced project, not intended for beginners

• Tree Fall Sound cannot be held responsible for any damages or injury which may result during assembly or usage

• Tree Fall Sound cannot be held responsible if your build does not function as expected

• All parts should be inserted from the side of the circuit board on which they are labeled (silk screened), then soldered from the opposite side. Installing on the wrong side, will cause problems, in most cases, Big problems. It's very difficult to unsolder a multi-pinned part like a header or jack without harming the board or part. If it becomes necessary and you find it difficult to unsolder a part, it's often best to just sacrifice it by cutting its leads then clearing the holes for a new part.

• If you choose to go FULL DIY and ignore the following instructions, please at least view the photo depicting each step (click on any photo to enlarge it) and read any instructions with bold text or a warning icon: . These are critical steps, or steps with quirks which might cause issues if not performed as suggested.

• Some steps have options to allow for system customization. Those are tagged with a question mark icon: It might be a good idea to consult the Customization guide and consider your customizations prior to building.

• We've tried to identify and iron out potential build issues, but you might encounter your own. Identifying a problem and figuring out a way to fix it is part of the fun of DIY. That said, if the instructions aren't clear, you run into problems or just have questions, post to the build forum or email: support@treefallsound.com

• It's advised to have the BoM pi-Stomp Core Bill of Materials handy (either open in a browser window or printed). The order of these steps roughly corresponds to the order of the BoM and was chosen to facilitate assembly. Could be helpful to check off each part in the BoM, once it's installed.

• Here is a good guide for soldering. In addition to that I have a few extra suggestions:
  • Keep your tip clean using a wire sponge or damp sponge or both. Oxidation (black stuff) prevents heat transfer and can result in cold joints. I suggest wiping it at least every 4 or 5 joints and definitely once when you're finished with a round.
  • It's tempting to just feed the solder into the iron. The flow of the solder follows the heat, so heat the pad and component lead for a second or two, THEN feed the solder into the junction. If the solder doesn't melt, pull the iron away and melt a dab of solder, then go back to heating the junction.
  • Don't apply too much solder (see guide below). Almost as soon as it flows, I stop feeding. Small diameter solder is recommended (0.8mm / 0.031“).
  • Keep the iron on the joint for a second or so after the solder flows.
  • Don't keep the iron on the joint any longer than necessary. Excessive heat can damage components.

• Good idea to inspect your soldering under magnification to assure you didn't bridge short any pads. The headers with 0.1” spacing are especially prone to this. You can check for shorts using a continuity meter. Here's an excellent guide to identifying other solder joint issues: Adafruit soldering guide - common problems

• Take your time! A rushed job during assembly could reward you with many hours of debugging later, or worse, a high tech doorstop. The possible bright side there, is that it's a fairly modular design and the most expensive components (Pi, LCD, audio board, IC's, etc.) are easily detachable. So if you mess up the board, a lot of the parts can be salvaged. If you're stuck with a build mistake, post to the build forum, or contact support@treefallsound.com for suggestions.

All Set? LET'S BUILD!

Here are the parts needed for assembling the pi-Stomp Core PCB

To save you from the often frustrating soldering of surface mount components, we've presoldered the voltage regulator for you. You're welcome!

• Bend the legs and insert all resistors R1, R2, R3 & R4 (2Meg) from the silkscreened side.
• Splay the leads slightly to keep them positioned
• Repeat for R5 (33 ohm - orange/orange/black/gold)
• R6, R7 & R8 are only required if you're going to be using the extra 3 GPIO pins (for LED's, etc.) and require a voltage drop / current limit. Calculate the value as appropriate for your load or add a simple wire jumper if you're using the GPIO as an input.

• Solder from the lead side and trim

• Insert C1 and C2 (red 0.1uF), splay leads (non-polarized)
• Insert C3 and C4 (smaller yellow 0.1uF), splay leads (non-polarized)
• Using needle nose pliers, straighten the pre-bent leads for the 10uF oscon capacitor C6 and insert. Make sure the negative lead, marked with the blue paint, goes thru the hole marked with “-” (also has a square solder pad)
• C5 should not be populated. Could help some situations, but generally makes noise worse than with no capacitor.

• Solder all pads, clip leads

• Trim the Fuse (looks like a ceramic capacitor) leads just above the bend:

• Insert (orientation doesn't matter). Solder, Trim.

• Insert both transistors (Q1 & Q2) with the flattened side matching the silkscreen. Splay the leads, solder, trim. Too much heat can damage a transistor, don't linger with the iron. If you can't solder in less than 3 seconds or so, attach a heat sink tweezer to the transistor side of the lead.

Many of the headers are optional and provide interfaces for your own customization. Good idea to check out the Customization guide and consider how you plan to customize, so you can choose the ideal configuration.

Pay close attention to which side the header should be inserted - the side with the silkscreened name. Unsoldering a misplaced header is not fun

It's important for headers to sit tight and perpendicular to the board. I use tape to keep it in place until a pin (or two) is soldered, then adjust as necessary before soldering the remaining pins

This header is optional but recommended if you might need access to extra GPIO pins for Outputs (LED's, etc.) or direct (not ADC or debounced) inputs.

This header can be installed on either side of the board. The top side (with the silkscreen next to the encoder) is generally more accessible until mounted inside an enclosure. Angle the pins slightly upward (maybe 10 to 15 degrees) so that jumpers can be attached and clear the IC which will be installed South of it later.

OR…

…for connections after mounting in an enclosure, you may prefer the header to be on the bottom side (side with red capacitors).

The build depicted from this point onward has the HGPIO header mounted on the bottom side.

• Secure with tape (or other means).
• solder

• Secure at both ends. Perpendicular as possible to the board..
• Solder. The 40 pins are rather close and solder bridges between pads would be bad, so take your time and don't over-solder

Depending on how you plan to enclose the pi-Stomp you might choose to use a different header or mount the LCD directly to the PCB.

If you want the LCD to be mounted underneath the top panel (requires a rectangular cutout - not trivial without a CNC or patience with a file), then you won't likely be able to use a plug-able header because that would place the top surface of the LCD above the pot and encoder. Soldering the LCD directly to the board, will result it the LCD face being just about where the pot and encoder go thru their enclosure holes. So in that case, skip installing this header and wait until the pot and encoder are mounted (last step), then solder the LCD directly to the board at a height that matches the pot and encoder. Some hot glue around the pins could increase mechanical stability.

If you want to be able to unplug/swap the LCD, then a header should be soldered instead of the display itself. The provided 1×9 female header should result in the display sitting on top of the enclosure top panel surface. Not quite as aesthetically pleasing, but it makes machining of the enclosure easier (only a narrow slot for the pins is required) and it allows for unplugging/swapping the LCD. The rest of the build instructions assumes this configuration.

These are the headers for the output and input jumpers. When complete they should look like this:

Note how the black plastic ends up perpendicular to the board not flush to it.

Use tape to secure each while soldering. It can help with positioning if you attach a jumper as it will be when eventually connected.

HOut header:

HIn header:

This provides the interface for attaching pushbuttons or footswitches which require debounce.

If you plan to mount pi-Stomp core into a very small enclosure (like a 1590BBS) and plan to have 3 footswitches, it has been done, but you'll likely find that some of the header pins will be obstructed by the middle footswitch. I was able to accommodate just the connections for the 3 footswitches by breaking the header down to a 2×3 and connecting only inputs 2, 3 and 4.

This is optional, but recommended unless it would interfere physically with external components. It exposes the UART of the Raspberry pi (pins 8 & 10) plus 3Volt power and ground. The most likely application is adding MIDI In and/or Out. Third party boards exist for this, or it's really easy to create your own. See pi-Stomp Customization guide for more info. Again, like the HSwitch header, if you plan to use a 1590BB enclosure with 3 footswitches, these header pins will likely be obscured. You could hard wire a ribbon cable to the board in that case.

This is optional but recommended unless you plan to repurpose it for direct SPI to your own hardware. It provides 8 analog inputs. See the Customization guide for how to use or repurpose as a direct SPI interface.

The sockets have a notch to indicate pin #1. Orient that to match the silkscreen notch.

• Insert S1 (14-pin). Secure (with tape, etc.) and solder

S2 (the ADC socket) is recommended for most builds unless you plan to replace the ADC with your own hardware connected via SPI (see the Customization guide)

• Insert S2 (16-pin). Secure and solder

• Insert S3 (8-pin). Secure and solder

• Insert Rly. Note the line across one end of the relay. This must end up at the end with the “Rly” board label as shown
• Secure with tape and solder. Note the pads are very small. Be sparing with the solder.

Make sure these are inserted from the correct board side. Unsoldering them is a bitch.

• Insert JPwr

• To increase mechanical sturdiness, before soldering, bend over terminals with a blunt, plastic utensil (eg. butt end of a Sharpie).

• Solder. Large pads so make sure you use plenty of solder.

• Insert JIn and JOut

• Secure solidly against the board
• Solder. Small pads, be sparing with solder.

• Insert Vol pot P1
• To increase mechanical stability, I recommend bending over the side tabs with a blunt plastic tool like the butt end of a sharpie

• Solder 6 pins plus the side tabs

The last part is often the trickiest. The encoder Enc has very short pins, but for it to sit tight against the enclosure face, it needs to sit at roughly the same level as the Vol pot. It should rest on its side tabs at the appropriate level, however, it can rock and end up not perpendicular to the board. So…

• Secure with tape on each side to make it perpendicular

• Solder just one of the 5 pins. Because of the short pins, you may need to solder from the top (encoder side) of the board.
• Make sure it's still as perpendicular as possible. If not, adjust. Reheat the solder if necessary. Once it's good, solder the remaining pins.
• Solder the side tabs to the pads on the top of the board (for mechanical stability)

Congratulations, the board is complete!

The pins of the IC's usually need to be bent inward just a millimeter or two before inserting. Lightly squeeze all pins between thumb and first finger.

All IC's are polarized. Make sure the notch/dimple (indicating pin #1) ends up on the same end as the silkscreen (and sockets if you installed them right). Worse case, match the photos below.

• Insert U1 (14-pin debounce chip: LS19-A)
• Insert U2 (16-pin ADC chip: MCP3008)

• Insert U3 (8-pin opamp: MCP6292-E/P)

Two jumpers attach the Audio Board to the pi-Stomp PCB.

• First cut a 3-wire jumper in half (color doesn't matter)

• Separate the individual wires (maybe 1 to 2 cm)
• Strip about 3mm from each wire and twist the copper strands
• Tin each end (heat and add just a spot of solder)
• Can be tricky holding the board, wire, iron and solder. A “third hand” helps, Also a pair of pliers with a rubber-band can hold the board. Worst case, ask a friend.

• Insert the 3 wire ends into the top (component) side of the board labeled “Input” and solder.

• Cut the other half to around 7cm (2.75“).

• Split off two of the 3 wires
• Strip and tin the two wires as before
• Insert the 2 wire ends into the top side of the board labeled “Output” but just the two outside pads, not “Gnd”

• Hold in place and Solder

The Pimoroni Hat Hacker should have included 6 10mm metal hex spacers and 12 metal screws. We'll use those along with the nylon spacers for assembling. We'll be using all the screws so try not to loose them.

Attach two 10mm metal spacers using two screws to the Audio Board

They should attach on the edge opposite of the 40-pin header

Attach two 12mm nylon spacers using two screws to the Hat Hacker

They should attach on either side of the edge 40-pin header (male pin side)

Attach two 8mm nylon spacers plus 1mm nylon washers to the Pi using two screws.

They should attach on the edge opposite of the 40-pin header. The stack results in a 9mm spacer.

The four boards should look like this.

Stack the Hat Hacker onto the Raspberry Pi. Seat completely and attach with two screws.

Stack the Audio Board onto the center 40-pin header of the Hat Hacker. Attach with two screws from below. Note that since the audio board has a short header, there will be a slight gap (~2mm) between male and female headers.

Stack the pi-Stomp board onto the main Hat Hacker 40-pin header. Seat completely and attach with two screws.

Connect the 3-pin Audio Board Input cable to the pi-Stomp board. Each pin is labeled on each board with “L” for left, “G” for ground, and “R” for Right. Make sure you connect like pins.

Similarly connect the 2-pin Output cable. It only has “L” and “R”, no ground.

Plug the LCD into the pi-Stomp board 9-pin header.

That's quite the sandwich, eh?