Which base
Three bases carry the same sixteen holes and the same battery circuit. The only choice is what a wire lands in: pins, push-in terminals or screw terminals, and how much board that takes.
One decision
The ESP32-C3 OLED board goes into two 8-way sockets on every base, so every base carries the same sixteen holes in the same order: GPIO 3 to 10 down one side, and GPIO 0, 1, 2, TX, RX, 3.3 V, ground and 5 V down the other. Every base also carries the same battery connector, charger and power switch, which have their own article.
What differs is what a wire lands in, and how much board comes with it.
The three, side by side
| Expansion base | Pluggable terminal base | Screw terminal base | |
|---|---|---|---|
| A wire lands in | 2.54 mm pin or socket | 3.5 mm push-in terminal | 3.5 mm screw terminal |
| Ways per side | 8 pins and 8 sockets, wired together | 8 | 8 |
| Board size | 39.5 × 32.5 mm | 53.1 × 32.5 mm | 44.5 × 32.5 mm |
| Tallest part, from the underside | 10.1 mm | 14.9 mm | 10.3 mm |
| Shop name | Expansion Board | Screwless Terminal Board | Screw Terminal Board |
Sizes are from each base's mechanical drawing. All three have two 4.8 mm mounting holes 16 mm apart.
What none of them changes
The board's own limits come with it. GPIO 5 and 6 are the display, GPIO 8 is the blue LED, GPIO 9 is the BOO button and GPIO 20 and 21 are the serial port, whichever base the board is seated on. The sixteen pins lists them. A base brings the holes out; it does not add a pin or take one away.
The board also works with no base at all. Its two rows are 17.78 mm apart, so it fits across the centre channel of a breadboard. What it lacks there is the battery.
When it does not work
The GPIO numbers belong to the C3 OLED board, so a sketch is the same on all three bases. The difference is a connection: a wire not pushed fully home in a push-in terminal, a screw not tight on a wire, or a jumper pushed into the strip of the wrong row.
It has all sixteen: eight on each side. On the expansion base each one comes out twice, as a pin and as a socket, and on the two terminal bases each one is one terminal. Count eight down each side, in the order printed on the base.
The board is not fixed to the base. It lifts out of the two sockets and goes into another base's, and nothing on the board changes. Check the way round again each time you seat it.
One of the two ways round is wrong, and the wrong one puts the battery rail on three of the chip's pins.
Seat the board first →Edit this page — content/books/c3oled/which-base.mdx
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