MF68 links

Some links on the MF68 PCB

68keys.io walks you through making your own custom keyboard using the MF68 PCB. It is very thorough. It covers parts selection, assembly and firmware.

keeb.io has a guide to replacing the PCB in a MagicForce 68 with the MF68 PCB. If you are in the USA you can purchase the MF68 PCB here.

If you are outside the USA it may be cheaper to have a PCB manufactured using the gerber files here.

4x4x4x4 with switch plate

48 key keyboard from three 4x4 PCBs

I made some PCB plates so that I can use plate mount switches.

The three 4x4x4x4x4 boards are connected together with solder bridges. 

The base is a 9x3" 1/8th thick 5052 aluminum plate I got off eBay. The aluminum is soft and I drilled it with a cordless drill.

 It is running the same TMK firmware as the other 4x4x4x4x4 board on git.

The plate was sanded with 220 grit wet/dry sandpaper. The raw edges were sharp and the drill holes had burs.

Plate mount switches. Without a plate these would have only the electrical contacts holding them in place, easy to bend or break.

The plate is on git. It has notches for switch top removal for compatible Cherry and Gateron switches.The holes are big enough to fit the tip of a screwdriver through but not big enough for the screw head, so spacers need to be installed before soldering in the switches.

Side view. You can see the plate, PCB and thick aluminum base. M2 spacer and screws hold the PCB to the aluminum base.

Closeup of the Arduino Micro clone. The sockets are the very low profile Peel-A-Way sockets.

Silent GNAP!

GNAP! with Cherry Silent Black Switches

GNAP! with PCB top and bottom plates. The plates were scuffed up with a Scotchbrite pad to dull the finish.

Blank DSA keycaps from PMK grab bag. Infected Smurf for scale

Scuffed up surface is dull and no longer reflective.

Cherry silent switches.

PCB plates held together with M2 spacers and screws.

Sockets

Lots of sockets

Some of the many sockets I use on my keyboards and other projects.

Front row left to right:

• MillMax standard socket (0.6" wide, 24pins, 2.54mm pitch)
• MillMax ultra low profile socket (0.6" wide, 24pins, 2.54mm pitch)
• Thomas & Betts CDF2024AU (0.6" wide, 24pins, 2.54mm pitch)
• Dual wipe socket (all others are machined pin sockets)

Top left:

• Standard snappable SIP socket 
• Low profile snappable SIP socket
• Extremely low profile Peel-A-Way socket

Top middle:

• Female square pin header
• Male pin header

MillMax sockets are from Mouser. The width is important if using these with Pro Micro's. They also come in narrower 0.3" and 0.4" wide versions. You will see lots of part numbers and prices. The low profile ones cost more than standard. Gold contacts/full gold flash coating add cost over plain tin. Plain non-gold work fine. Gold is only worth it if you are concerned with corrosion.

The other sockets are from eBay or other electronics supply.

Close up of the SIP sockets. Besides "standard" and "low profile" they are made in many different heights. If buying from someplace like Digikey or Mouser they will have precise figures and mechanical drawings to reference. Buying from eBay you don't really know what you will be getting unless they list part numbers you can lookup.

Close up of the male and female pin headers. These are not IC sockets. They are board connectors for connecting two PCBs together. The male pins usually come with Pro Micros. The female receptacles you can order from electronics supply stores. They are very common on Arduino shields.

Bottom of the MillMax sockets. The low profile socket has thicker pins that are hollow. The pins of the IC passes through to the bottom.

Snappable SIP (Single Inline Package) headers have notches where you can break them into smaller sections. They don't always break cleanly.

Peel-A-Way is a brand of frameless sockets. The thin kapton plastic holds them together while soldering, then you peel the strip off and only the pins remain. They also make DIP (Dual inline package) arrangements and have full height pins as well as the low profile ones.

These are hard to find. I got mine from an electronics surplus store, and they have no more. I see some types on eBay once in a while. Keeb.io now has them for a really low price.

When using sockets with a Pro Micro you may have to cut off some of the cross supports.

You could use the pin headers to make a Pro Micro removable, but they are very tall compared to IC sockets.

You do not want dual wipe sockets. They are designed for the thin flat pins of a DIP IC.

A few more sockets from EMC and Augat. These were purchased on eBay. New old stock.

The green socket is full gold flash coated. The blue has only the contacts plated in gold.

A MillMax socket on the left, a cheap eBay socket from China on the right. The cheap socket works fine, is a bit taller than the MillMax.

16mm Keycaps

Chiclet style keycaps fit 16mm spacing

These double shot acrylic keycaps are exactly 16mm at their widest part, near the base. They fit the 16mm switch spacing of my smallest boards without any modifications.

These are made of acrylic and were purchased from FlashQuark.com. They come in a 104key set in either black or white with clear legends.

Shiny acrylic. If you don't like shiny keycaps you won't like these.

While they fit fine, their shape makes it difficult to not press more than one key at a time. This might actually be good for stenography where you often want to press multiple adjacent keys simultaneously.

The edges along the bottom of the keycaps can have a lip that catches on the other keycaps when pressed. Running your fingernail or some other hard object around the edges will flatten them. I only had a few keycaps that would stick.

Happy Pi Day

MX Pie

Quarter segment PCBs. Constructed in a similar way as the 4x4 PCBs, but in a radial pattern. The matrix for each quarter is 4x3, with 10 keys each. The four quarters combined is a 4x12 matrix

It is powered by a single Pro Micro. It could be built as a single segment or two/three. The board edge has cutouts to help align the pieces.

3 quarters in yellow PCB would look like PacMan.

Gerbers on git. There is also a JSON file for use with kbfirmware.com.

The outer row are alternating 1.75U, and 1.5U keycaps. Third row is 1.5U keycaps. Second row 1.25U, center 1U/1.25U.

Sunflower. This is an earlier version of the board that uses a Arduino Micro instead of a Pro Micro. These are PCB mount switches without a top plate.

I used a 1/8th thick 5052 aluminum circle I bought off eBay. I taped a set of PCBs to the top and used it as a guide to drill the mount holes.

Pro Micro from the side. M2 spacers and screws. There is a reset switch near the Pro Micro. There are also pads for a TRRS jack, but I have not tested a split version yet.

Top and bottom of the PCB.The edge cutouts are keyed and can not be assembled incorrectly.

 Quarters un-assembled. I use solder bridges to hold the segments together. The solder bridges also create the electrical connections between the segments.

The top plate has the same shape as the PCB. The radial pattern is not perfectly symmetrical so the top aligns with the PCB in only one orientation. It is not possible to use PCB mount switches with the plate. This is due to a slight difference in the rotation of the switch footprint vs. the cutout in the plates. They are very close but not exact. Plate mount switches fit fine.

No idea what this would be useful for. It was mostly an experiment to make something circular and play with interlocking board shapes.

Contra

Contra 40% ortholinear keyboard kit

This is a very inexpensive kit from Cartel.ltd that includes everything except switches and keycaps. The top and bottom plate are both PCB material with white soldermask. The kit was $30 plus shipping, this was through a group buy.

I assembled it using switches and keycaps recycled from a Leobog K22 104 key keyboard I got from Amazon for $17. This is the full grid layout with 48 keys. It can also be assembled with a 2U space bar. You will need to provide your own PCB mount stabilizer for the 2U keycap.

The bottom plate is a PCB. They used a solid copper fill on the bottom and used the soldermask layer to display their logo in reverse. The exposed area is HASL coated. The bottom is reversible, the other side is mostly blank. The 3M black rubber feet were included in the kit.

Side view of the three parts. The PCB is screwed to the bottom with M2 spacers and screws. The switch plate sits on top and is only held in place by the switches. The kit came with 8mm spacers. I used my own 5mm spacers with a washer (0.3mm thick) to make it as thin as possible. The tallest part is the USB connector on the Pro Micro. I could also make it thinner by using a thinner Pro Micro. The black Pro Micro clone came in the kit, it is socketed in an ultra low profile socket.

The linear red K RGD switches from the Leobog keyboard. The plate and PCB should also work with Alps switches.

The switches have 19.05mm spacing, which is the standard. It also makes these parts incompatible with OLKB.com Planck parts which have 19mm spacing.

I added a WS2812B strip to the bottom. There is a 4 pin header to the right of the reset switch.
Ground, B1, F7, VCC. I used a modified version of my GNAP! firmware on mine. The matrix is the same shape, just different pins. They also have an online firmware compiler but it is very limited. You can export the JSON from there and upload it to kbfirmware.com where you will have access to more features, including support for the WS2812B strip.

Closeup of the 4 pins. I used B1 to control the WS2812B strip. The reset switch is a nice feature since the Pro Micro doesn't have one. Makes it a little easier to deal with the caterina bootloader. I flashed my Pro Micro with the DFU bootloader.

All lit up. The white soldermask reflects the light well.

There are only 5 M2 supports. This is probably not enough for this board if you are a heavy typist. There is quite a bit of flex.

Black Arduino Micro Clone

Not so great

I needed more Arduino Micros and the green Arduino Micro clones have been out of stock on Aliexpress for a while. The genuine Arduino Micros are more than $20 each. You can find these black Arduino Micro clones on Amazon in a three pack for under $20. They sell them with and without the headers installed. I got the ones without headers so I can solder on pins that can be socketed in an IC socket.

The one improvement that this clone has over the green and regular Arduino Micro is a micro USB connector that has mount supports that go through the board, not just stuck to the surface. This should make the connector harder to break off.

The major downside is the huge crystal they put on the bottom of the board. It sticks out 4mm. This makes it impossible to use with a low profile socket. The green Arduino Micro clone has no components on the bottom.

Side view showing how much the crystal sticks out the bottom. With a full height socket the metal case has less than 1mm clearance from touching the PCB.

I hope the green clones are eventually restocked. I have ordered some blue clones from Aliexpress, those have the same design as the genuine Arduino Micro, and have components on the bottom, but not a the huge crystal.

Planck PCB Rehab

Replacing the bootloader on a Planck PCB

OLKB has released a custom LUFA bootloader that has audible and visual feedback when in bootloader mode. Newer PCBs come with it preinstalled. I have an older Rev 4 board that has a speaker but the old boring bootloader that does not click.

I had previously soldered wires to the ISP pins on the Planck PCB to flash the bootloader. The Rehab uses pogo pins (like the Lobot) to make electrical contact with the same ISP pins without soldering.

You could also use this to gain 4KB of flash memory for your compiled firmware by eliminating the bootloader completely. That would let you use the full 32KB, but lose the convenience of flashing via DFU.

Gerber files on Git.

The Rehab is a Lobot with pogo pins in specific locations that match the Planck PCB. The P75 E2 pogo pins worked best. The larger T2 heads are close to touching with the tight spacing.

The six ISP pins. Reset, Ground, SCLK, MOSI, MISO, VCC.
SCLK, MOSI, MISO are PB1, PB2, PB3 on the Planck PCB.

I used 6mm M2 spacers and nylon screws on the bottom to prevent electrical shorts.

You'll need one hand to hold the Rehab in place against the solder pads while running Avrdude with the other.

I compiled the QMK modified LUFA DFU bootloader from here https://github.com/qmk/lufa/tree/master/Bootloaders/DFU

I also tried this with a Rev 2 PCB and the positions of the ISP solder pads were the same. I do not know if the Rev 5 or Preonic PCB will work, but from the pictures I have seen it looks like the ISP pins are in the same location and spacing.