Specifications
| In the range | The ESP32-C3 OLED board, and three bases it seats on: expansion (2.54 mm pins and sockets), pluggable terminal (3.5 mm push-in) and screw terminal (3.5 mm screw) |
|---|---|
| Chip | ESP32-C3FH4, single-core RISC-V up to 160 MHz, 4 MB flash inside the module, 400 kB SRAM, no PSRAM; Wi-Fi 4 and Bluetooth LE; the USB-C socket goes straight to the chip, so there is no driver to install |
| Display | 0.42 in OLED, 72 × 40 pixels, SH1106 at I²C address 0x3C, on GPIO 5 (SDA) and GPIO 6 (SCL) |
| Holes | 16 on the board and on every base: GPIO 3, 4, 5, 6, 7, 8, 9 and 10 down one side, and GPIO 0, 1, 2, TX (21), RX (20), 3.3 V, ground and 5 V down the other. Six are answering to something before your sketch runs: 5 and 6 (display), 8 (blue LED), 9 (BOO button), 20 and 21 (serial) |
| Board size | 25 × 20.5 mm, the two rows of holes 17.78 mm apart |
| Edge connectors | Expansion: 8 pins and 8 sockets a side at 2.54 mm, wired together. Pluggable: 2 × 8 push-in terminals at 3.5 mm. Screw: 2 × 8 screw terminals at 3.5 mm |
| Base size | Expansion 39.5 × 32.5 mm, screw terminal 44.5 × 32.5 mm, pluggable terminal 53.1 × 32.5 mm |
| Tallest part | Measured from the underside of the base: expansion 10.1 mm, screw terminal 10.3 mm, pluggable terminal 14.9 mm |
| Mounting | Two 4.8 mm holes, 16 mm apart, on each base |
| Battery | JST PH 2.0 two-pin socket for a single 3.7 V lithium cell with a protection circuit; TP4054 linear charger, which takes the cell to 4.2 V; a slide switch between cell and board |
| Battery monitor | An open solder jumper marked BATTERY MONITOR and IO2 joins two 100 kΩ resistors across the cell, halved, to GPIO 2. It ships open |
Seat the board the right way round, every time. Antenna at the power-switch end, USB-C at the battery-connector end. Turned around, it fits just as firmly and the base's battery rail lands on GPIO 3, 4 and 5. Plug the cable in only after the board is seated.
What is here
The ESP32-C3 OLED is a 25 × 20.5 mm board with a 72 × 40 display soldered to it and two of its GPIOs spent on that display before you start. On its own it runs from USB. Seated on a base it also runs from a lithium cell, and brings its sixteen holes out to something a wire can land in.
Four products share this page, because the question anybody holding one asks is the same: which way round, and which hole is which. The handbook has shared chapters for what is true of all of them and a chapter for each base.
Which one
| OLED board | Expansion base | Pluggable terminal base | Screw terminal base | |
|---|---|---|---|---|
| What it is | The board | Pins and sockets | Push-in terminals | Screw terminals |
| A wire lands in | a 2.54 mm hole | 2.54 mm pin or socket | 3.5 mm push-in | 3.5 mm screw |
| Battery, charger, switch | none | yes | yes | yes |
| Size | 25 × 20.5 mm | 39.5 × 32.5 mm | 53.1 × 32.5 mm | 44.5 × 32.5 mm |
| Best for | a breadboard | jumpers, breadboards | wiring that changes | wiring that travels |
All three bases bring out the same sixteen holes in the same order, so a sketch does not change from one to another. Which base is the one-page version of this decision.
Wiring, in four lines
- Seat the board with the antenna at the power-switch end and the USB-C
socket at the battery-connector end. Match
V5on the board to5Von the base. - Plug the USB cable in after the board is seated.
- For a battery, plug a protected 3.7 V lithium cell into the JST socket, with
the
+on the silkscreen beside the positive pin, and move the switch to ON. - In the Arduino IDE choose ESP32C3 Dev Module and set USB CDC On Boot to Enabled.
Where to start
New to the board: what you are holding, then the sixteen pins. Holding a base: which base, then seat the board first, then the chapter for yours.
When it doesn’t work
- Which way round does the board go on a base?
- Antenna at the power-switch end, USB-C at the battery-connector end. The check that needs no memory: find V5 on the board and 5V on the base and put them at the same end. The board fits turned around just as firmly, and that way the base's 5 V pad meets the pin marked 3, so the battery rail drives three chip pins.
- Which base should I buy?
- Jumper wires and breadboards: the expansion base, which is also the smallest. Bare wire you change often: the pluggable terminal base, push-in with no screwdriver. Bare wire that has to stay put: the screw terminal base. All three bring out the same sixteen holes and carry the same battery circuit.
- Does a sketch need changing between bases?
- No. The GPIO numbers belong to the board, and every base brings out the same sixteen holes, so a sketch is the same on all three.
- Why does the base's charge LED not light when I plug in USB?
- The switch has to be ON, with a battery connected. With the switch OFF the cell is out of the charging circuit, and the charge LED can flicker so fast it looks half-lit. The cell is not charging in that state.
- Why is GPIO 2 not free when I use the battery level?
- The BATTERY MONITOR jumper connects the divider across the cell to GPIO 2. It ships open so the divider does not draw from the cell; bridge it only if you will read the level, and GPIO 2 is spent from then on.
- Why does the board fail to join my Wi-Fi?
- The antenna is a ceramic chip a few millimetres long, and at full transmit power the radio overdrives it. The back of every base prints WIFI_POWER_15DBM to 8_5DBM: setting the power down to 8.5 dBm in the sketch is what makes the board stay on a network.
- Do I need a driver?
- No. The C3 has its own USB peripheral, so the board appears as a serial port with nothing to install. Set USB CDC On Boot to Enabled in the Arduino IDE, or the sketch runs and prints nothing.