Device cheat-sheet — Guition JC3636K518C

One page. Every pin below was cross-checked against the Waveshare schematic and verified on a unit. The board header in the starter template is the only place pin numbers belong in code.

Identity

Field	Value
Model	JC3636K518C_I_YR1 (“K5 Knob Series”), Guition / Shenzhen Jingcai
Twin	Waveshare ESP32-S3-Knob-Touch-LCD-1.8 (same PCB, blue case)
Display	1.8” round IPS, 360 × 360, ST77916 over QSPI, RGB565, colours inverted
Main MCU	ESP32-S3R8: dual-core 240 MHz, 8 MB octal PSRAM, 16 MB QSPI flash, Wi-Fi + BLE 5
Second MCU	ESP32-U4WDH sidecar (Classic BT audio). Runs stock firmware. Treat as opaque.
Inputs	Capacitive touch (CST816D) + rotary knob. No push button.
Feedback	Screen + haptic (DRV2605L + LRA). No LED ring, no speaker.
Storage	microSD slot (SDMMC 4-bit), shipped card is a 480 MB SDSC
Audio	PCM5100A DAC, line-out 3.5 mm jack only; PDM MEMS mic

ESP32-S3 pin map

Display (ST77916, QSPI on SPI2)	GPIO		Touch (CST816D, I2C)	GPIO
SCK	13		SDA	11
CS	14		SCL	12
D0 / D1 / D2 / D3	15 / 16 / 17 / 18		INT	9
RST	21		RST	10
TE	not wired		DRV2605L haptic	same bus, addr 0x5A
Backlight	47 (LEDC PWM, off at boot)

Knob (detector switches)	GPIO		microSD (SDMMC 4-bit)	GPIO
EC1_A	8		CLK	4
EC1_B	7		CMD	3
			D0 / D1 / D2 / D3	5 / 6 / 42 / 2

Other	GPIO	Notes
PDM mic clock / data	45 / 46	Strapping pins; inputs only, fine
Battery / rail sense	1	ADC1_CH0, ×2 divider on the system rail, not the cell
USB D− / D+	19 / 20	Native USB-Serial/JTAG

Reserved pins — never drive these

GPIO	Why
0	BOOT strap and I2S mux select and exposed on the expansion header. On-board pull-up. Leave it alone.
38 / 48	UART to the ESP32 sidecar (TX / RX)
39 / 40 / 41	I2S to the DAC (BCK / WS / DOUT); DAC mute is owned by the sidecar

What this board does NOT have

No LED ring · no speaker or amplifier · no push button on the knob · no TE (vsync) line · no quadrature encoder (see gotchas) · no OTA partitions in the template (single 9 MB app).

USB: the cable orientation picks the chip

You see	Chip	Port	Use
303a:1001 Espressif USB JTAG/serial	ESP32-S3	/dev/ttyACM0 (Linux), /dev/cu.usbmodem* (macOS), COMx	This is the one you flash
1a86:7523 CH340	ESP32 sidecar	/dev/ttyUSB0, /dev/cu.wchusbserial*	Not ours. Flip the plug.

lsusb (Linux) or system_profiler SPUSBDataType (macOS) tells you which one you got.

Flash recipe (host, never the container)

# After scripts/build.sh produced build/ — run on the HOST, from the template root
esptool --chip esp32s3 --port /dev/ttyACM0 --no-stub \
  --before default_reset --after hard_reset write_flash \
  --flash_mode dio --flash_size 16MB --flash_freq 80m \
  0x0     build/bootloader/bootloader.bin \
  0x8000  build/partition_table/partition-table.bin \
  0x10000 build/knob_starter.bin

• --no-stub is mandatory on this board’s native USB serial; with the stub it stalls.
• First flash must be the full set (bootloader + partition table + app) because the 16 MB partition table differs from stock. After that 0x10000 app alone is enough.
• If the port vanishes: hold BOOT while tapping RESET to force download mode.
• Monitor: esptool does not monitor; use python3 -m serial.tools.miniterm /dev/ttyACM0 115200 or idf.py monitor only if you have a native IDF.

Top 8 gotchas

1. The knob is not a quadrature encoder. Two detector switches to GND, idle high; one detent is one clean low pulse on exactly one channel and which channel encodes direction. Poll at 3 ms and debounce in pure code. PCNT/rotary-encoder drivers read garbage.
2. GPIO0 is triple-booked. Never configure it as an output. Driving it low around reset puts the chip in download mode and silences the audio path.
3. Invert colours exactly once. The panel needs inversion (0x21 in the init table). Doing it both in the init table and via esp_lcd_panel_invert_color() gives a negative image.
4. Internal RAM is the scarce resource. 8 MB PSRAM is plenty; the ~512 KB internal SRAM is shared by Wi-Fi, lwIP, mbedTLS and task stacks. Keep LVGL’s pool in PSRAM, keep the draw buffer small (~20 rows) and internal, stream uploads through one 16 KB chunk.
5. No TE line means tearing on full-screen animations. Partial refresh, calm motion.
6. Strapping warnings on 45/46 are normal. They are mic inputs. Do not “fix” them.
7. Touch and haptic share one I2C bus. Init the bus once; the DRV2605L is at 0x5A.
8. The backlight is dark until driven. GPIO47 has a pull-down; if the screen is black after flashing, check the LEDC init before suspecting the panel.