Drone Motor Carrier
Public Made by Adomby adom
Passive baseplate for the single-motor drone test cell: mounts the BLDC motor, passes its three phases through, routes two load-cell channels, and nests the RP2350A/ADS1220 acquisition molecule and a PiProbe over a 96 x 96 mm machine-pin datum. 104 x 104 mm, 4-layer.
Motor Carrier v1.1 — Function
104 × 104 mm, 4-layer JLC04161H-7628, 2.000 mm corner arcs. Machine-pin datum 96.000 × 96.000 mm.
Carries the motor, passes the three phases from the ESC through to the motor leads, and hosts the RP2350A+ADS1220 molecule (N2) and a PiProbe (N1).
Analogue routing
The machine contacts sit upstream of the molecule's RC filter, so anything the carrier picks up arrives unfiltered at the bridge's 350 Ω source. The layout follows from that:
- Pair pitch 0.450 mm, constant over the entire run on both channels
- Lengths 22.75 / 23.47 mm (ch1) and 44.08 / 43.31 mm (ch2)
- All four pairs on B.Cu, no vias, referenced to In2 GND 0.2104 mm away
- In2 plane coverage 91–96 %; every gap is a pad antipad
- Nearest same-layer neighbour 2.04–3.08 mm; nearest phase copper 4.53 mm
- Digital crossings run on F.Cu with two GND planes between
+5V_REF1 and +5V_REF2 are separate nets with no carrier-side tie to +5V. They merge only
inside the molecule. See 03-Molecule/Overview.md for the ratiometric topology this preserves.
UART arbitration
The FC and the nested PiProbe both reach the molecule's RX line. debugprobe drives its UART TX from power-up regardless of USB enumeration, so a populated probe holds that pin continuously.
Net-(N1-TX) : N1.9 (PiProbe TX), R1.1 two pads only
/UART0_RX : MC18 (FC), N2.14 (molecule RX), R1.2
R1 = 300R 0603 1 % sits on a 4.31 mm stub in the PiProbe branch alone. The probe reaches the net only through R1; the FC and the molecule's RX connect directly.
contention 3.3 / (300 + 50 + 50) = 8.25 mA
R1 dissipates 300 x 8.25mA^2 = 20 mW of 100 mW
FC drives 0 3.3 x 50/400 = 0.41 V valid LOW
R1 is not in the BOM — it has no LCSC field.
Phase path
Three large contacts (Ø2.62 hole / Ø4.40 ring, ~20.8 A each), one per phase, into a 4-layer pour with 49 vias at 2 mm pitch per phase, out to 8 × 8 mm wire pads with a 2.0 mm hole.
Phase copper is 12.02 mm × 4 layers = 1.207 mm², 0.214 mΩ over the 15 mm run.
Harness rules
/nRSTreaches both MC16 (FC) and MC13 (Scaffold). Wire one end only, or make both open-drain. There is no external pull-up on either board — only the RP2350's internal 32–86 kΩ./SWDand/SWCLKon MC22/MC24 are an external-probe landing. Keep them out of the FC harness./I2C0_SCLand/I2C0_SDAon MC20/MC21 have no destination; the FC carrier has no I2C contacts.
# Motor Carrier v1.1 — Function
104 × 104 mm, 4-layer JLC04161H-7628, 2.000 mm corner arcs. Machine-pin datum 96.000 × 96.000 mm.
Carries the motor, passes the three phases from the ESC through to the motor leads, and hosts the
RP2350A+ADS1220 molecule (N2) and a PiProbe (N1).
## Analogue routing
The machine contacts sit **upstream** of the molecule's RC filter, so anything the carrier picks up
arrives unfiltered at the bridge's 350 Ω source. The layout follows from that:
- Pair pitch **0.450 mm, constant over the entire run** on both channels
- Lengths 22.75 / 23.47 mm (ch1) and 44.08 / 43.31 mm (ch2)
- All four pairs on B.Cu, no vias, referenced to In2 GND 0.2104 mm away
- In2 plane coverage 91–96 %; every gap is a pad antipad
- Nearest same-layer neighbour 2.04–3.08 mm; nearest phase copper 4.53 mm
- Digital crossings run on F.Cu with two GND planes between
`+5V_REF1` and `+5V_REF2` are separate nets with **no carrier-side tie to `+5V`**. They merge only
inside the molecule. See `03-Molecule/Overview.md` for the ratiometric topology this preserves.
## UART arbitration
The FC and the nested PiProbe both reach the molecule's RX line. debugprobe drives its UART TX from
power-up regardless of USB enumeration, so a populated probe holds that pin continuously.
```
Net-(N1-TX) : N1.9 (PiProbe TX), R1.1 two pads only
/UART0_RX : MC18 (FC), N2.14 (molecule RX), R1.2
```
**R1 = 300R 0603 1 %** sits on a 4.31 mm stub in the PiProbe branch alone. The probe reaches the net
only through R1; the FC and the molecule's RX connect directly.
```
contention 3.3 / (300 + 50 + 50) = 8.25 mA
R1 dissipates 300 x 8.25mA^2 = 20 mW of 100 mW
FC drives 0 3.3 x 50/400 = 0.41 V valid LOW
```
R1 is not in the BOM — it has no LCSC field.
## Phase path
Three large contacts (Ø2.62 hole / Ø4.40 ring, ~20.8 A each), one per phase, into a 4-layer pour
with **49 vias at 2 mm pitch** per phase, out to 8 × 8 mm wire pads with a 2.0 mm hole.
Phase copper is 12.02 mm × 4 layers = **1.207 mm², 0.214 mΩ** over the 15 mm run.
## Harness rules
- `/nRST` reaches both MC16 (FC) and MC13 (Scaffold). Wire one end only, or make both open-drain.
There is no external pull-up on either board — only the RP2350's internal 32–86 kΩ.
- `/SWD` and `/SWCLK` on MC22/MC24 are an external-probe landing. Keep them out of the FC harness.
- `/I2C0_SCL` and `/I2C0_SDA` on MC20/MC21 have no destination; the FC carrier has no I2C contacts.