Verified 2026-10

m5stack Atomic toChain Base

Atom-to-Chain adapter: 9-pin Atom bottom header out to one HY2.0-4P (GND/5V/IO1/IO2), default IO1/IO2 = GPIO22/GPIO19 on an Atom Lite and G5/G6 on an AtomS3 - $2.95 USD, no silicon aboard.

Place this board on a carrier in the editor →

Logic level3.3 V

Part & documents

Source	shop.m5stack.com/products/atomic-tochain-base →

Pinout

5 pads, as the vendor numbers them.

#	Name	Function	Signals
1	3V3	Atom bottom-interface pad 1 - 3.3 V, right-hand column of the vendor table.	3.3 V rail
3	IO1	Atom pad 3 - IO1, the first of the two Chain signal lines.	Chain IO1, default GPIO22 (Atom Lite) / G5 (AtomS3)
5	IO2	Atom pad 5 - IO2, the second Chain signal line.	Chain IO2, default GPIO19 (Atom Lite) / G6 (AtomS3)
6	5V	Atom pad 6 - 5 V, left-hand column of the vendor table.	5 V rail
8	GND	Atom pad 8 - ground, left-hand column of the vendor table.	ground

Power

Input	3V3 and 5V pass through from the Atom bottom header
Typical draw	0 mA

Notes

The vendor's 9-pin Atom table labels only pads 1, 3, 5, 6 and 8; pads 2, 4, 7 and 9 are blank there and are left out of pins[] rather than guessed. No datasheet_url: the board is a passive adapter with no silicon. The IO mapping is set by 0 ohm resistors (R2 and R7 fitted by default) and reserve solder pads, per the schematic, not by the product page - the product page shows only a connection diagram image.

AI context

Dense context for pasting into a model prompt — addresses, pinout, voltages, tolerances and the vendor's reference circuit.

PART: M5Stack Atomic ToChain Base, SKU A163, a 31.0 x 24.0 x 11.8 mm (4.3 g) adapter that carries the Atom series controller's 9-pin bottom expansion interface out to a male HY2.0-4P connector for Chain-series devices. There is no silicon on the board - it is a connector, two 0 ohm resistors and a set of reserve solder pads - so the entry has no headline part and no data sheet.
ADDRESSES: none. The board carries no bus device.
PINOUT: the Atom-side header is the vendor's own 9-pin table (PIN | LEFT | RIGHT | PIN), and the vendor labels only four of the nine: pin 1 = 3V3, pin 3 = IO1, pin 5 = IO2, pin 6 = 5V, pin 8 = GND. Pins 2, 4, 7 and 9 are blank in that table and are recorded here as absent rather than filled in. The Chain side is one HY2.0-4P: Black GND, Red 5V, Yellow IO1, White IO2.
DEFAULT IO: the vendor's default mapping is Atom Lite -> IO1 = GPIO22, IO2 = GPIO19; AtomS3 / AtomS3R -> IO1 = G5, IO2 = G6. The schematic selects those defaults with R2 and R7 fitted as 0 ohm links; the other options it draws are GPIO19, GPIO21, GPIO22, GPIO23, GPIO25 and GPIO33, each reachable by removing the 0 ohm resistor and shorting the reserve pad to the IO you want (R3, R4, R5, R6, R8 to R12 are marked NC on the shipped board).
SUPPLY: 3V3 and 5V pass through from the Atom bottom header to the HY2.0-4P Red and the Atom pin 1; the board regulates nothing and draws nothing on its own.
LOGIC: whatever the Atom drives - 3.3 V. IO1 and IO2 are straight copper from the Atom pads to the connector, with no series resistor, no buffer and no level shift.
CIRCUIT: no pull-ups, no decoupling, no ferrite. The only parts fitted are the connector, the 9-pin header and the two 0 ohm links.
TRAPS: (1) IO1 and IO2 are not fixed pins - they land on different Atom GPIO depending on which 0 ohm link is fitted, so code written for GPIO22/GPIO19 is wrong on an AtomS3. (2) Changing the mapping is a solder job on reserve pads, not a switch. (3) The 9-pin Atom table leaves four pads unlabelled, so a designer cannot assume those are grounded.

Provenance

Every figure on this page was read from the 3 sources below and last checked on Oct 30, 2026.