Up to four W/s can be connected together via an expander PCB dubbed slashes. This board supplies shared power and i2c busses for direct W/-to-W/ communication (forthcoming).
There are two main configurations for this expander PCB, which differ in their placement of the power & i2c headers on the PCB: REAR MOUNT, and SIDE MOUNT.
The REAR MOUNT configuration allows for up to four W/s to connect, while increasing the depth of the modules (53mm required).
The SIDE MOUNT configuration allows joining up to 3 modules, preserving the original depth (39mm), while extending the connectors to the left beyond the module's denoted width.
Rear-mount configuration is recommended unless your skinny skiff is less than 53mm deep. Side-mount configuration works in shallower cases, however the board will stick behind the module to the left. This means the module next to it must be shallower than 30mm depth! All other mannequins modules (except RIP) satisfy this requirement.
If you're not geeked on DIY, you can buy a preassembled slashes direct from us over here.
Populating the PCB is slightly different depending on your configuration, and how many modules you wish to support. Below are Octopart BOMs for each of the 5 possible configurations.
You'll need the PCB available direct from Oshpark. They'll make you 3 boards, so feel free to on-sell the blank pcbs, or completed boards.
Additionally, it's recommended you install a few components to provide pull-up resistance for the i2c connection. Indeed this is necessary if you only plan to use W/-to-W/ communication. If you already have a powered Teletype busboard providing the i2c connection to slashes, then pull-up components are not necessary. Otherwise, you should install them. NB: Any values between 2k2 and 4k99 are suitable for the pull-up resistors.
- Soldering Iron
- Box Cutter / Knife
- Needle Nose Pliers / Edge cutters
Cutting the PCBOshpark PCBs often have small perforated tabs on the edges. Snip the board down to a rectangle with edge cutters, or score with the knife, and snap with needle-nose pliers.
There are 5 components to add to the board: a 3.3V Voltage Regulator, 2 bypass capacitors (0.1uF), and 2 resistors (2k2 to 4k99). These components provide pull-up resistance.
For each component, add solder to a single pad, pick up the component with tweezers in one hand, reheat the soldered pad with the iron in your other hand, then slide the component into place. Remove the iron, followed by releasing the tweezers once the joint has solidified. Solder the remaining pads.
Adding Top-Side Female Headers
Populate the female power and i2c headers column-by-column, from right to left. Begin by placing solder on one of the corner pads for the first power header and the first i2c header.
Use tweezers to hold the i2c header while your using the soldering iron to heat the soldered pad. Slide the header into place while the soldering iron is still heating the pad. You want each of the pins to be sitting squarely centered on their pads. If you aren't immediately satisfied with the alignment, take the time to adjust it until it's nicely centered in the pads.
Once you're aligned, solder the rest of the pins in place on both sides of the header.
Repeat this process for this column's power header.
For the next columns, it's best to begin by placing solder on the corresponding corner pads that are not adjacent to the first column. Once you have each header in place, solder the outside pads before moving to the pads between the two headers.
Hold the soldering iron vertically in order to fit in the narrow space between the two headers. Avoid touching either header as the soldering iron will melt the headers – they smell terrible!
Repeat the process for any further columns you wish to add.
If you using the rear-mount header, jump straight to the next section!
To add the side-mount power headers, you will utilize two mounting holes between the pads for each of the two headers. The bottom side of each header has two mounting posts which align the headers on the PCB.
Begin with the i2c header. Once the header is in place with the posts sitting in their mounting holes, solder the outer pins. Soldering the inner pins can be tricky so take your time, starting with the middle-pin. Try holding the iron horizontally.
Next is the power header using the same technique. You may not be able to reach the middle pin on the inner row, that's ok! – you already have 5 other ground pins.
Flip the board over. Use the same process as before to add the two male headers. Make sure to line up the notch on the shrouded power header with the white line on the circuit board's silkscreen. There should be a small arrow on the shrouded header which will line up with the white line on the PCB. The header's key is boxed in red below.