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8x8 LED matrix/The board/01. The six pins
The board · 01 of 10

The six pins

Six pins, five of them wired. GND, VCC, CS, DIN, NC and CLK from the left with the matrix up. There is no square pad on this board, so count from GND, and the pin marked NC is connected to nothing at all.

Updated 2026-09-254 min read8x8 LED matrix

What it is

Sixty-four red LEDs in one square package, and a chip under it that keeps a picture in its own memory and lights it for you. Your board sends the picture as eight bytes, once. After that the display looks after itself until the next picture arrives.

The TK52 seen from the front: a black board almost entirely covered by a square 8 by 8 grid of round LED dots, a strip of board below it with two round mounting holes at the corners, and between them a right-angle six-pin header whose pins lie flat toward the bottom edge, printed GND, VCC, CS, DIN, NC and CLK from left to right.
The front. The matrix covers the top 32 mm of the board; the header is along the bottom.

The header is right-angled: the pins lie flat over the board and end at its bottom edge, so it sits on a breadboard edge or takes a cable.

The six names

The six pins, and the back
Show
Pins to wire
5 of 6
Square pad
none
Pitch
2.54 mm
NC means not connected. The pad is soldered to a header pin, and no trace on the board reaches it: in the net list it belongs to no net. Wire it or leave it, nothing changes. It is there so the six-pin order matches the chainable module's.

GND is the left-hand pin. On most TinkerBlock boards GND is also the square pad; on the TK52 all six pads are the same oval, so the printed name is the only mark. Count from it.

VCC feeds the chip and every LED. It goes to 5V, whatever voltage your board's own pins run at. 5 V on VCC, 3.5 V for a HIGH is the reason.

CS, DIN and CLK carry the picture: DIN the bits, CLK the moment each bit is read, and CS the moment a whole message takes effect. Sixteen bits and a latch follows one message down them.

NC means not connected, and here it means exactly that: no trace reaches it. It sits between DIN and CLK, so a wire meant for CLK that lands one pin to the left goes nowhere and the display stays dark.

The back

The back of the TK52: a black board with two columns of eight gold pads down the left and right edges where the matrix's legs come through, a box reading TK52 and MATRIX LED, the words DISPLAYS PATTERNS TEXT, OR GRAPHICS USING 64 LEDS, lonely binary in large letters, and six oval header pads along the bottom labelled CLK, NC, DIN, CS, VCC and GND from left to right.
Turned over, the names read the other way: CLK on the left, GND on the right.

The two columns of eight pads are the matrix's sixteen legs. Everything else the board carries is on the front, under the matrix.

When it does not work

Which pin is GND without a square pad?

Hold the board with the matrix facing you and the header at the bottom. GND is the left-hand pin, and it is printed beside the pin on the front. Turned over, the back prints the same names mirrored, so GND is on the right.

Does NC need a wire?

No. The pad marked NC has a header pin soldered to it and no trace on the board reaches it. Wiring it to something does nothing, and leaving it empty does nothing. It keeps the six-pin order the same as the chainable module's.

Can I use DIN, CLK and CS on any pins?

Yes. The book's sketch drives all three by hand, so any three output pins work. It uses each board's hardware SPI pins so that the wiring still suits the SPI library if you move to it later.

Where is DOUT?

There is none. The MAX7219 has a DOUT pin, and on this board it reaches no pad. That is why a TK52 cannot pass data on to a second matrix. The chainable module in the 3-pack is the one with an OUT edge.

Alongside this page
SPI and chip select3.3 V and 5 V logic
Where this goes next

The matrix, and the three parts it hides: the chip, the resistor that sets the current, and a capacitor.

What is on the board →

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