Pinouts

tinySpeak uses the following tinyCore GPIO pins. These pins are in use whenever the HAT is mounted — avoid assigning them to other peripherals in your own sketches.

tinySpeak PCB schematic overview

Speaker — MAX98357A (I2S Output)

Signal	GPIO	Description
BCLK	9	Bit clock
LRC	10	Left/right clock (word select)
DOUT	8	Serial data output to amplifier

Initialize the audio output in your sketch with:

audio.setPinout(9, 10, 8); // BCLK, LRC, DOUT

Microphone — SPH0645LM4H-B (I2S Input)

Signal	GPIO	Description
SCK	13	Bit clock
WS	11	Word select
SD	12	Serial data input from microphone

The SPH0645 requires 32-bit stereo Philips mode via the ESP-IDF I2S driver (i2s_std.h). The demos read both stereo channels and extract only the left channel, shifting the 24-bit data down to 16-bit PCM:

wav_buffer[i] = (int16_t)(raw_samples[2 * i] >> 14);

Headphone Jack — TLV9062 (Analog Output)

The 3.5mm jack is driven by the TLV9062 dual op-amp and provides an analog headphone output. This is a separate signal path from the speaker amplifier — no firmware configuration is required. Disconnect the speaker if you want clean headphone-only playback.

Optional Button (Active-Low)

Signal	GPIO	Description
BTN	RX	Active-low, internal pull-up enabled via `INPUT_PULLUP`

The button is wired between the RX pin and GND. See Adding the RX Button in the Overview for assembly details.

Reserved Pins Summary

GPIO	HAT Function	Notes
8	Speaker DOUT	I2S TX data to MAX98357A
9	Speaker BCLK	I2S TX bit clock
10	Speaker LRC	I2S TX word select
11	Mic WS	I2S RX word select
12	Mic SD	I2S RX data
13	Mic SCK	I2S RX bit clock
RX	Button (optional)	Active-low, internal pull-up

All other tinyCore GPIO pins remain available for your own use when the tinySpeak HAT is mounted.