RotaryCell / build guide

Add the LilyGO connections

Add and label each group separately. The overview and close photographs below show the connector orientation and routing used in the working build.

Four prepared LilyGO harnesses laid out before installation

Four harnesses attach to the LilyGO. From left to right in the photograph:

Harness	Connections
Charging input	10 cm pair from regulated 5 V and system GND
21700 battery	10 cm pair from cell positive and cell negative to `BATN`
AG1171 carrier power	10 cm pair from LilyGO `VBAT` and system GND
AG1171 carrier signals	Four 10 cm conductors for GPIO15 `FR`, GPIO16 `RM`, GPIO37 `SHK` and GPIO21 `PD`

Throughout this build, black is negative and yellow identifies unswitched battery positive. The blue wire in the four-conductor signal harness is an orientation marker; compare its position with the completed-board photographs before inserting the contacts into the housing.

The current-carrying red, yellow and black conductors shown here are 24 AWG. The signal-only conductors are 28 AWG. These are the gauges used in the working build; the signal currents themselves are small.

Battery and protected-system power

Connect the prepared 21700 leads to the LilyGO battery-positive and BATN points formerly used by the holder. The AG1171 carrier receives positive power from the LilyGO VBAT pad and returns through LilyGO system GND. Its ground does not connect directly to BATN.

Yellow battery-positive and black battery-negative leads attached after removal of the original holder

The yellow and black battery leads leave opposite ends of the former holder area. Keeping both at 10 cm provides enough lead to reach the 21700 without leaving a large loop inside the phone.

Audio and tone

The Audio/Reset A4 harness uses the GPIO36 audio signal, GND, SPEK+ and MIC+.

Leave SPEK- insulated and floating.
Connect MIC- to system ground through the external nonpolar 1 µF capacitor used in the tested build.

Contact side of the corrected four-position LilyGO audio connector — Viewed from the contact-window side, the corrected connector carries the GPIO36 audio signal, GND, `SPEK+` and `MIC+` from left to right. Identify each conductor by its termination rather than its color.

The signal-only conductors in this harness are 28 AWG. Cut and prepare them as follows:

Connection	Color	Length	Preparation
Common ground	Black	14 cm	Leave loose for its LilyGO connection
GPIO36 tone	Blue	18 cm	Leave loose for its LilyGO connection
`SPEK+`	Red	10 cm	Installed in the two-position SPEK connector
`MIC+`	Red	10 cm	Installed in the two-position MIC connector
`SPEK-`	Black	—	Remove this conductor from the SPEK cable
`MIC-`	Black	Start with 10 cm	Leave long initially; cut to fit when soldering the capacitor and ground connection

Both audio connector branches begin as 10 cm cables. Removing the black SPEK- conductor leaves the speaker connector intentionally one-sided. The black MIC- conductor remains in its connector until the harness is installed, then is trimmed to the required route.

Corrected four-position audio harness connected to the Audio and Reset board — The same corrected harness installed at the top of the Audio/Reset A4 board. Check continuity by signal name from this connector back to the LilyGO before applying power.

Installed SPEK and MIC connectors, common lead, tone lead and MIC reference capacitor

The close view shows the two audio connectors at the end of the controller and the reference capacitor fitted before the wiring is dressed into the carrier.

AG1171 control

The carrier logic harness uses GPIO15 for FR, GPIO16 for RM, GPIO37 for SHK, and GPIO21 for PD. Record the connector orientation before inserting the contacts into their housing.

The connector remains outside the controller outline while its individual conductors follow the edge of the board. The 10 cm signal wires are long enough to reach the carrier without adding unnecessary slack. Confirm all four positions with a meter rather than inferring their order from wire colors.

Hardware reset

Connect the A4 reset header by signal name:

Audio/Reset A4	LilyGO connection
U2 pin 1, `SW_BAT`	Center terminal of the LilyGO power switch
U2 pin 2, `RAW_BAT`	Battery-side switch pad shown in the installed close-up
U2 pin 3, `RESET`	GPIO35

The first two connections bridge the physical power-switch path so the A4 board can remove and restore battery power. Before soldering, use continuity mode to confirm the center terminal and the battery-side pad on your board revision; do not identify either connection by wire color alone.

Prepared three-wire hardware-reset harness

For the reset harness shown above:

Signal	Length	Gauge
`SW_BAT`	16 cm	24 AWG
`RAW_BAT`	16 cm	24 AWG
GPIO35 `RESET`	18 cm	28 AWG

The extra 2 cm on the green trigger wire allows it to follow the required route without pulling against the two power-switch conductors.

Close view of the power-switch taps and lower GPIO connections

The two battery-path conductors start at the switch points. The longer GPIO35 trigger lead starts farther down the controller and joins them after following the board edge, which accounts for its additional 2 cm.

Charging

Bring regulated 5 V from the selected rear connector to the LilyGO charging input and system ground. Keep this charging input separate from the AG1171 carrier's battery supply.

Arrange and strain-relieve the new wiring so both USB ports and both QWIIC connectors remain accessible.

Dress the wiring into the carrier

Seat the LilyGO fully in the printed carrier. Route the audio, reset and control conductors through its open channel so they leave together near their destination boards. The shorter power and connector leads only need to clear the carrier edge. Nothing should cross a USB port, press on the power switch or pull against a solder joint when the carrier is set down.

Prepared LilyGO seated in its printed carrier with the corrected harnesses routed through the open channel — The prepared controller seated in the carrier. The loose connectors remain accessible for installation while the conductors pass through the carrier without loading the solder joints. Identify the audio conductors by GPIO36 audio signal, GND, `SPEK+` and `MIC+`, rather than by color.