CAN tap

Boards / lift ESC DroneCAN daughter board

The CAN tap connects one lift ESC to DroneCAN bus 1.

Revision: A draft
Sheets: 1
Parts: 13
Location: aircraft
Bus: DroneCAN bus 1 (lift ESCs only) on our FC
Status: Rev A draft: schematic only

What it does

The CAN tap is a daughter board for the lift ESC. It holds the bus side of the ESC: the CAN transceiver, the bus connectors, the terminator, the ESD protection and a fusible CAN ground. The ESC board carries only a four-wire logic link to it.

The CAN parts moved off the ESC on 2026-10-05 (Ryan). The ESC board was too full to route on any layer count. The bus parts also belong with the harness. Thus an ESC can be replaced without a change to the bus.

The fusible resistor connects CAN ground to board ground. If the power return of the pod fails, it opens. Then the CAN ground wire cannot carry motor current.

Where it sits

There is one CAN tap for each lift ESC, in the pod. th-blender selects one of two shapes:

Shape	Location	Size
A	A strip in the spar bore, behind the two feed capacitors	About 8 x 28 mm
B	At the harness tap on the boom, in place of the joiner of the pod	About 24 x 10 mm, 1.0 mm FR-4

The board is only for the DroneCAN pod path. The TBS Lucid 4-in-1 flies first, with no nodes on bus 1.

Main parts

Part	Function
SN65HVD230	3.3 V CAN transceiver, high-speed mode, 1 Mbit/s
Two JST SM04B-GHS-TB	Bus in and bus out connectors
120 ohm resistor and solder jumper	Terminator. The jumper is open at delivery, because terminator plugs in the harness end the bus
NUP2105L	ESD protection on CAN_H and CAN_L
Kamaya FRC32 10 ohm	Fusible resistor from CAN ground to board ground
100 nF and 1 uF	Decoupling for the 3.3 V supply from the link

Connections

Connector	Type	To
J1 (CAN_IN)	JST GH-4: 1 CAN_VCC, 2 CAN_H, 3 CAN_L, 4 CAN_GND	Bus 1 harness
J2 (CAN_OUT)	JST GH-4, same pinout	Bus 1 harness to the next pod, or a terminator plug
Link pads	Four 1.5 mm pads: 3V3, GND, TXD, RXD	Lift ESC, four 28 AWG wires

Pin 1 goes from J1 to J2 and connects to nothing else. Bus 1 carries no VCC. The ESC supplies the 3.3 V for the transceiver through the link.

Status

Rev A draft, 13 parts. The schematic is generated from gen/design.py: ERC 0 errors. There is no layout. No part is taller than the GH-4 housings (4.35 mm). The AM32 target does not change. The next steps are the shape, outline, height and plug directions from th-blender, and the link length from th-main. Then the layout starts. The link must be less than about 100 mm.

Schematic and layout

Files

can-tap.kicad_sch

From the EDA repository at revision b201257 (2026-10-12). Open the files in KiCad 10 or later.