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Razer Orbweaver Chroma MCU mod

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4) Disassembly.

It's a pain to take an Orbweaver apart. There are lots of interconnected pieces that are hard to disassemble in a clear step by step process. The following geekhack post has lots of pictures:  I also found the following Youtube videos very useful:

Schematix: Tuffrabit:

General advice:

Be patient, take your time, and don't try to force anything.
There are two ball bearings with springs used for the adjustable pads. These can (and will) go flying!  So you may wish to do the initial disassembly in a contained area like a dry bucket until you know where those components are and can make arrangements to extract or contain them. Some discussion about the ball bearings can be found here:
Keep the pieces organized for later reassembly. I used a sheet of clean clear polypropylene to store the sticky pads. 
When removing the keyboard PCB, be very careful not to break the ABS plastic tabs that hold it down.  They are not very flexible, and break easily.
The cosmetic sticker on the thumb pad must be removed to get the thumb assembly apart. I gave up on trying to save it. But YMMV.

5) Modifying the plastic parts.

To make room for the RP2040 and ribbon breakout board, you'll need to remove some of the ABS plastic on the bottom tray.  To accomplish this I used a combination of tools including wire dykes, x-acto chisel, and razor blade. The pictures below show before and after images of the tray, pointing out in RED where the plastic must be cut. The rightmost picture shows where the new components will go. In order to fit, the corner of the RP2040 board must be rounded slightly with a file (2 millimeters). But leave enough material to support the USB housing. Note the upside-down placement of the ribbon breakout board - this is the orientation it will have when connected to the keyboard above it by a folded (but not twisted) ribbon cable.  Also note the 1cm wide section of plastic removed from the fin separating the MCU and breakout board - this is needed for the wire bundles running between the MCU and the breakout board.

Also shown is the placement of the (optional) lever microswitch, used as a dedicated mode toggle. It also plays a secondary role in confining the RP2040 to a fitted rectangular area, making it MUCH easier to secure in place, and more resistant to movement when the USB cable is plugged-in an un-plugged.

6) Wiring.

Shown below is a wiring diagram for the mod.  The terminals marked "GPX" refer to the terminal position on the microcontroller (this is the nomenclature used by QMK - in the RP2040 documentation they are marked as "DX":  GP 2, 3 are SDA and SCL for the I2C. GP 4~7 are the rows of the keypad. GP 12~16 are the columns. GP 8 & 9 are rows 5 & 6 (for the thumb pad keys).  Also required are 5V, GND, and 3.3 V (for the I2C pull-up resistors).

There is not enough room under the keyboard for a pin header, so I recommend direct wire connections among the RP2040, IS31 interface board, and breadboard. The 8 row x 4 pin section of stripboard fits nicely under the palm rest area just inside the hole for the wire bundle running to/from the thumb pad. In the original unit this wire bundle ends in a 14 pin JST connector, which can be cut off to gain access to the correct wires (GND, TRQ, PNK, WHT, GRY PRP, BLU, GRN). 

The photo below shows how it should look after wiring everything together (warning: some of the wire colors in this photo differ from the circuit diagram due to lack of some colors in my wire inventory).  Note that the ribbon breakout board must be flipped upside down in the final assembly to avoid twisting the ribbon.  For this reason, it is best to feed the wires from the bottom, so they enter from the top when it is flipped upside-down.

7) MCU Retainer and optional mode switch. 

I wanted to avoid dedicating any regular keys or thumb buttons (or defining key combos) to toggle keymaps. So I added an optional mode switch. As shown in the first set of figures, this required drilling a hole in the side of the Orbweaver for a button stem, which actuates a micro arcade lever switch. I used epoxy to fix the switch in place.  In subsequent versions of the mod I also glued a piece of PC board (" x " ) on the top of the switch to help align the movement of the mode button and keep it from falling out of the hole. The mode switch is incorporated into the rest of the key matrix by wiring one end to row 6 (GP 9) on the stripboard, and the other (via diode) to column 2 (GP13).

As shown in the pictures, this piece of PC board also  to prevent the retainer plate from sliding out of the dovetail joint.   

You will also need to make a retainer plate for holding the Elite Pi in place.  Fortunately Razer provided the perfect part for this in the original unit!  It's a small plastic plate with a notch and a cylindrical plastic pin (used originally to hold the USB cable in place).  Unfortunately we had to remove the two screw mounts for this plate to make room for the RP2040. But that's OK, because it turns out the micro arcade switch described above is in the perfect size (" x ⅜" x ") to support one side of the plate (while the other is supported by the original plastic dovetail).

Cut the length of the plastic pin on the retainer plate to 3.5 mm, and then add layers of 3 mm EPP foam (commonly used as packing foam) to both sides, and glue in place with CA glue or epoxy.  Position the switch (or alternatively a block of wood or plastic of the same size) just to the right of the RP2040, such that the MCU cannot slide around laterally.  Then glue the switch (or block) in place with epoxy.  After the glue hardens, glue a piece of PC board (" x " ) on the top of the block to prevent the retainer plate from sliding out of the dovetail joint. (If you installed a switch, this is the same PC board you installed to confine the button.)  As shown in the pictures, when the retainer plate is put in place, the foam on top of the plate brings it's net height up to the bottom plane of the keyboard, such that the retainer plate is held down by the keyboard once it is installed. The 3.5 mm plastic pin points downward, making contact to the top of the USB3 connector, holding down the RP2040 very securely (while the downward facing foam gently limits lateral motion). 

This type of switch also has the added benefit of boxing in the RP2040, making it MUCH easier to secure in place.  In fact

The mode switch is incorporated into the rest of the key matrix by wiring one end to row 6 (GP 9) on the stripboard, and the other (via diode) to column 2 (GP13). 

that's a very quality post for a newcomer tbh


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