What is on the board

The TK103 is a PCM5102A DAC, a 3.5 mm stereo jack and a red power LED on a TinkerBlock board. Six pins go to the ESP32-S3: ground, 3.3 V, the two clocks, the data and XSMT, which a resistor on the board already holds HIGH. It is a 3.3 V board, and it comes in one box with the TK100 amplifier and the TK101 microphone.

Updated 2026-09-245 min readI2S DAC

One box, three blocks

The I2S audio kit laid out: the TK103 DAC on the left with its headphone jack at the top and six pins along the bottom printed GND, 3V3, BCK, DIN, LRCK and XSMT; the TK100 amplifier and TK101 microphone on the right; a teal box printed I2S AUDIO DEV KIT; a 3.5 mm to RCA cable, a 3.5 mm to 3.5 mm cable, and a small black speaker with red and black wires. — The TK103 comes in the I2S audio kit, headers fitted.

The kit holds the TK103 DAC, the TK100 amplifier, the TK101 PDM microphone, a 4 Ω 3 W speaker that plugs into the TK100, a 3.5 mm to 3.5 mm cable and a 3.5 mm to RCA cable. The ESP32-S3 and the jumper wires are not in the box.

Six pins to the ESP32-S3

The TK103 from directly above: a black 3.5 mm jack standing off the top edge, the twenty-legged PCM5102A below it between two round LEGO holes, small capacitors and resistors around it, a red LED at the bottom left, and six right-angle pins along the bottom printed GND, 3V3, BCK, DIN, LRCK and XSMT. — Jack at the top, header along the bottom.

Pin	The chip calls it	Wire it to
GND	AGND	GND
3V3	AVDD, CPVDD, DVDD	3V3, never 5 V
BCK	BCK, bit clock	GPIO 42
DIN	DIN, data	GPIO 41
LRCK	LRCK, left/right clock	GPIO 40
XSMT	XSMT, soft mute	GPIO 39, or nothing

The GPIOs are the ones every sketch in this book uses. They leave the TK101's and the TK100's pins free, so any two blocks of the kit can be wired at once.

What is on the board

GPIO 42

Pin or part

Wire it to

GPIO 42

A clock, made by the ESP32-S3. The board never drives these; it only listens. Any free GPIO works, because the ESP32-S3 can route I2S to most pins. The book uses GPIO 42.

Everything on the header is an input to the board. The ESP32-S3 makes both clocks and the data; the TK103 only listens. BCK, DIN and LRCK each pass a 22 Ω resistor on the way to the chip, which softens the edges of fast clocks on a jumper wire.

XSMT is already HIGH

XSMT is wired straight to the chip and to a 10 kΩ resistor up to 3V3. With nothing connected it reads HIGH, which means play. A sketch may drive it LOW to mute, and XSMT: a mute that ramps shows what that does, but it never has to.

A 3.3 V board

The PCM5102A runs from 3.0 to 3.6 V, with an absolute maximum of 3.9 V, and the supply pin is printed 3V3. It draws about 20 mA, typical.

The red LED is lit from 3V3 through 5.1 kΩ. It says the board has power and nothing about sound.

When it does not work

Can I power it from 5 V?

No. The PCM5102A runs from 3.0 to 3.6 V and its absolute maximum is 3.9 V, so 5 V on the 3V3 pin is past the limit. The supply pin is printed 3V3: take it from the ESP32-S3's 3V3 pin.

Do I have to connect XSMT?

No. A 10 kΩ resistor on the board pulls it up to 3V3, and HIGH means play. Connect it only if you want the sketch to mute the output: driving it LOW ramps the sound down.

Can I use other GPIOs than the book's?

Yes. The ESP32-S3 routes I2S through its GPIO matrix, so any free GPIO works: change the numbers at the top of the sketch. Avoid the strapping pins 0, 3, 45 and 46, the USB pins 19 and 20, and 35 to 37 on boards with octal PSRAM.

The LED is lit but nothing plays.

The LED only says the board has power. Check the three signal wires against the pin numbers in the sketch, then work through When it stays silent.

Alongside this page

ESP32 pins you cannot use Pull-up and pull-down resistors

Where this goes next

How the chip makes its own clock from BCK, and the one setting that stops it.

Three wires, no master clock →

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