The ribbon, or the row of holes
Beside the row of eight holes every board has a 15-way, 1.0 mm socket, U31, that carries the same eight signals to a cable. Seven of its fifteen contacts go nowhere, and the contacts face the board: the silkscreen says PINS FACE DOWN.
Two ways onto one circuit
Step the signal control through the eight. Each line is one copper path on the
board: a contact of the 15-way socket U31 and a hole of the row are two places
to reach the same net. Seven of the fifteen contacts are NC, not connected to
anything, so a cable into the socket and eight jumper leads into the row are the
same wiring done two ways.
Step the board control and only the panel's own socket changes. That is the fact the family rests on: a circuit built around the 0.96 inch takes the 3.5 inch without a wire moving, because nothing in the wiring is specific to the panel.
Contacts down
A cable fits the socket either way up, and only one of them works. The board tells you which: PINS FACE DOWN is printed beside it, and the exposed contacts of the cable go towards the board.
The socket is a flip-lock: a bar on its far side lifts, the cable slides in until it stops, and the bar presses down. Neither movement takes force.
A cable in upside down is indistinguishable from no cable at all, and it is the first thing to check on a board that has never shown anything. Pin 1 is GND, at the end marked 1; before the first power-up with a cable you have not used before, it is worth a continuity check from that pin to the GND of the host.
The other end
The far end of the cable needs a 15-way, 1.0 mm socket to go into, and the signals have to arrive where the library expects them. The library's wiring defaults are the Lonely Binary breakout's, for whichever ESP32 you picked in Tools ▸ Board. On any other host, wire the eight signals yourself and tell the library where they went: the wiring article shows how.
The shortest cable that reaches
The 6-pack ships three lengths. Take the shortest one that gets there.
The cable is flat and unshielded, and it carries a clock that is 20 MHz on the
two ST7735 boards and 40 MHz on the other four at the library's defaults. That
works, and works less well the longer the cable. The symptom is a picture that
arrives scrambled, or draws halfway and stops, rather than one that fails
cleanly. If a long cable does that, the two fixes are a shorter cable or a
slower clock, and the library takes the clock as one call before begin().
If you are not using the cable
Snap eight pins off a header strip and solder them into the row. Straight points out of the connector face; right-angle points along the board, which is what you want if it is going to stand upright in a case.
Eight wires then go to your board, and they are the eight signals the socket carries. Which GPIO each of them wants is the next question after that, and the answer depends on your microcontroller and not on your panel.
When it does not work
Contacts down, towards the board. The silkscreen says PINS FACE DOWN beside the socket because a cable will physically seat either way up and only one of them makes contact. A cable in upside down behaves exactly like a cable that is not plugged in at all.
It is a flip-lock FPC socket: lift the bar on the far side gently, slide the cable in until it stops, then press the bar down. It takes almost no force in either direction. If you are pushing hard, the bar is still closed.
Usually the cable. A long flat cable carrying a 20 or 40 MHz clock is an unshielded line doing something it only just manages. Try the shortest cable you have, and if that fixes it keep the short one or call setSpiHz with a lower number before begin().
No. The panel's own socket has a different number of ways, and on most boards a different pitch, from the 15-way one: 8, 10, 12 or 14 ways, at 0.5 mm except the 2.4 inch at 1.0 mm. The orange tail of the glass is already in it. Nothing you wire goes there.
Then use the row. Solder a header into the eight holes (the 0.96 inch model shows one fitted; the others show bare holes), and wire those eight to your board with jumper leads. It is the same eight signals either way. The socket is a convenience and not a different interface.
A tour of the one circuit: the sockets, the backlight switch, the capacitors and the jumpers.
What is on the board →Edit this page — content/books/lcd/the-ribbon-or-the-header.mdx
Questions about this product
See what other owners have asked, and read their solutions.
This page covers several products. Choose yours to see the right discussions.
Discuss this article
Ask about this page. The answer stays here, on the page it belongs to, for whoever hits the same wall next.