Three boxes, one adapter

The TinkerBlock TK85, the soft keypad 5-pack and the heavy-duty 2-pack carry the same adapter circuit. What differs is the keypad, which half of the eight-pin join each part has, and the board the adapter is built on.

Updated 2026-09-264 min readmatrix keypad

Three boxes

The TinkerBlock TK85 comes in the 46-piece kit. It is the adapter on a TinkerBlock board: black with a gold edge, two round holes that push onto the LEGO base plate, and TK85 printed on the back. The keypad's header of eight right-angle pins leaves its top edge and the four pins for your board leave its bottom edge.

The TK85 at an angle: a black board with a gold edge, eight right-angle pins along the top edge, the 16-pin chip below them with two small capacitors to its right, two round LEGO holes, a keypad-and-finger drawing, two small resistors at the lower right, lonely binary up the left edge, and four right-angle pins along the bottom edge over their half-hidden GND, VCC, SDA and SCL labels. — The TinkerBlock TK85. The keypad plugs onto the pins at the top; your board's four wires go on the pins at the bottom.

It is photographed with a soft membrane keypad, the same kind as the 5-pack's, whose ribbon socket pushes onto the top header.

The soft keypad 5-pack has five flexible membrane keypads and five adapters, in a storage box. Each keypad is 69 × 76 mm with an adhesive back, and its eight wires run down a ribbon tail that ends in a socket. Keypad and tail together are about 160 mm long.

The heavy-duty 2-pack has two keypads in a rigid plastic frame with sixteen separate raised keys, and two adapters. Each keypad has eight pins soldered along its bottom edge, and its adapter has a socket for them.

The two packs' adapters are the compact form: a bare 20 mm square, with no LEGO holes. Two forms of the adapter lines them up against the TK85.

What is in the box, and how it joins

TinkerBlock TK85

Your box

Keypads

Adapters

Adapter form

Keymap to load

soft

One adapter circuit in every box; the keypad is what differs. The adapter's v2 form, on a TinkerBlock board with two LEGO holes. Its keypad header is eight right-angle pins, and the soft keypad it is photographed with plugs on the way the 5-pack's does; its four bus pins leave the bottom edge.

The joins

A TK85 pushed onto a blue LEGO base plate beside a green development board, four jumper wires from the board to the TK85's pins on the left, and a soft membrane keypad's clear ribbon plugged onto the TK85's eight pins on the right, the keypad lying flat on the desk. — The TK85 on a base plate: four wires to the board on one side, the keypad's ribbon on the other.

Soft pack: the ribbon's socket goes onto the compact adapter's pins. Keep the keypad's face and the chip facing the same way.

A heavy-duty keypad with black raised keys 1 to 9, A to D, star, 0 and hash, standing upright, its eight pins pushed down into the black socket along the top of the adapter board below it. — Heavy-duty pack: the keypad's eight pins go down into the adapter's socket.

The two packs' adapters are the same board with a different connector: right-angle pins on the soft pack's, an eight-way socket on the heavy-duty pack's.

Front and back of the heavy-duty pack's compact adapter side by side: a tall black eight-way socket along the top edge, the chip on the front, and on the back the labels TK85, GND, VCC, SDA and SCL, three address pads marked A0, A1 and A2, and the I2C PULL UP pad. — The heavy-duty pack's adapter. Its back is the same as the soft pack adapter's: four bus pins, three address pads and the pull-up pad.

Which keymap

The two keypads bring their wires out in a different order, so they need different keymaps. The TK85 is photographed with the soft keypad, and with that keypad it uses the soft map. One adapter, two keymaps explains why, and the first keypress has both maps ready to paste.

When it does not work

The soft keypad's socket went on, and every key prints the wrong character

The socket has no key, so it fits the adapter's pins either way up. Turned over, every key still works but the rows and columns land on different chip pins. Refit it with the keypad's face and the adapter's chip facing the same way, as in the photos, or run the keymap finder and use whatever map it prints.

One row of keys is dead after plugging in

The socket is one pin off, so one wire has no pin and one pin has no wire. Pull it off and line up all eight — the socket should cover the row of pins exactly, with nothing left over at either end.

Can I use a soft keypad with the heavy-duty pack's adapter?

Not directly: the ribbon and that adapter both end in sockets. Eight male-to-male jumper wires will join them. Keep them in order, then run the keymap finder, because a crossed pair changes which map is right.

Did my TK85 come with a keypad?

The TK85 is photographed with a soft membrane keypad on its ribbon, and the workshop's keypad lesson expects one, but no listing of the kit says it in words. If yours has none, any 4 × 4 keypad with an eight-way tail fits the header; run the keymap finder for its map.

Alongside this page

The other TinkerBlock parts, if the TK85 came in the 46-piece kit

Where this goes next

The TK85 and the compact adapter in the packs: the same circuit on two boards, and the one difference that changes a sketch.

Two forms of the adapter →

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