What is on it

The panel's ribbon in a 12-way socket, a BSS138 transistor and two resistors that switch the backlight, 10 µF and 100 nF across 3V3, and two solder jumpers that ship open. No regulator, no level shifter. The glass is sold as 1.8-inch; its drawing measures the picture at 1.77 inches, 128 by 160 pixels.

Updated 2026-09-265 min read1.8-inch TFT

A board that is mostly wiring

The front of the TK89, lying landscape with the header on the left: a black board with rounded corners and four round holes, eight pins out of the left edge labelled BL, RST, DC, SCL, MO, CS, 3V3 and GND from the top, a steel-framed screen filling most of the board with a blue strip along its left edge, and lonely binary printed up the right edge. — The front. The panel fills it; the header comes out of the short edge on the left.

The screen side carries the panel and nothing else. Every part is on the back: the socket the panel's ribbon plugs into, the switch for the backlight, two capacitors and two pairs of solder pads.

What is on the back

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An N-channel MOSFET in the backlight's return: its gate is BL, its source GND, its drain the backlight through R6. HIGH on BL lets current through it and the backlight lights; LOW, or nothing, and it blocks. It is a switch your pin drives, so the pin never carries the backlight's current.

U7 is a 12-way ribbon socket with a hinged latch, contacts 0.5 mm apart. Contact 1 is the backlight's return, 2 to 4 are 3V3, 5 and 11 are GND, 6 to 10 are RST, MOSI, SCL, DC and CS, and 12 is connected to nothing. Q2, R2 and R6 switch the backlight. C8, 10 µF, and C16, 100 nF, sit across 3V3 beside the socket. SB3 and SB2 are the BL-3V3 and CS-GND jumpers, both open.

A photograph of the back of the TK89 stood portrait with the header at the bottom: TK89 1.8 inch TFT in a white box at the top, pads marked BL and 3V3 beside a small three-legged transistor, two tiny capacitors, the white ribbon socket with the orange ribbon running down into a slot, a boxed warning about 5 V boards, pads marked CS and GND, and the pins labelled GND, 3V3, CS, MOSI, SCL, DC, RST and BACKLIGHT. — The back, photographed stood portrait: the ribbon runs from the socket down into its slot.

There is no regulator and no level shifter. What arrives on 3V3 reaches the glass, and so does every signal.

1.77 inches, sold as 1.8

The back prints 1.8" TFT and ST7735 128X160. The panel's drawing measures its picture at 35.04 by 28.03 mm, a diagonal of 44.9 mm: 1.77 inches. Displays are sold by that diagonal rounded to one decimal, so a 1.77-inch panel is sold as a 1.8. The controller is Sitronix's ST7735S.

The glass

Measure

Diagonal

1.77 in

Pixels

160 × 128

Per inch

116

Sold as 1.8 inches and printed 1.8" on the back. The drawing measures the picture's diagonal at 44.9 mm, which is 1.77 inches. It is the same glass: displays are sold by the diagonal rounded to one decimal, and 1.77 rounds to 1.8.

On this board the panel lies on its side: 160 pixels across and 128 up, with the header to its left. The ribbon leaves the glass on that edge, where the blue strip is, folds behind the board and comes up through a slot to the socket. A pixel is 0.219 mm, about 116 to the inch.

When it does not work

The board says 1.8 inch and the panel's drawing says 1.77. Which is it?

Both. The picture's diagonal is 44.9 mm, which is 1.77 inches, and displays are sold by the diagonal rounded to one decimal. It is the same 128 by 160 glass either way.

The ribbon has come out of the socket. Can I put it back?

Usually. Lift the socket's latch gently, slide the ribbon fully in with its contacts toward the socket's contacts, and press the latch down. Do it with the power off. A creased or torn ribbon cannot be repaired.

Is there a regulator, so I can feed it 5 V?

No. 3V3 goes straight to the panel and to the backlight's anode. There is no regulator and nothing to shift 5 V signals down, so the supply and every signal must be 3.3 V.

Does it have an SD card slot like other 1.8-inch boards?

No. Some 1.8-inch display boards carry a microSD socket; this one has only the display, the backlight switch and the jumpers.

Alongside this page

A MOSFET as a switch What a decoupling capacitor does

Where this goes next

Why nothing on this board may see 5 V, and how an Uno gets round it.

Three volts only →

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