V-DRIVE HAT Board Bring-Up Plan
Scope
Bring up the V-DRIVE HAT mezzanine board for a LILYGO T-SIM7600G-H R2 module. The HAT provides protected vehicle 12V input, an MP1584 12V-to-5V buck, CAN1 via ESP32 TWAI transceiver, CAN2 via MCP2515 plus CAN transceiver, a status LED, stacking headers, and a vehicle connector.
Pre-Power Inspection
- Confirm J2 is the intended mechanical vehicle connector. Current schematic uses a 16-pin right-angle placeholder because a keyed OBD-II J1962 footprint was not found in the library.
- Inspect D2 polarity: anode toward F1 / +12V_FUSED, cathode toward +12V_PROT.
- Inspect D1 TVS polarity: cathode to +12V_PROT, anode to GND.
- Verify no solder bridges on U4, U2, U1, U3, and J1 headers.
- Confirm CAN termination population strategy: RT1 and RT2 are fitted only if this board is at the end of each CAN bus.
Power Bring-Up
- Do not plug in the LILYGO initially.
- Apply current-limited bench supply to J2 pin 16 and GND pins 4/5. Start at 12V with a conservative current limit.
- Measure +12V_RAW at J2 pin 16, +12V_PROT at U4 VIN / D1 cathode, and verify the D2 diode drop.
- Measure +5V at U4 output / L1 / C10 / J1 +5V pin. Expected: about 5.0V.
- Check U4 temperature and input current under no load.
- Connect a dummy 5V load before connecting the LILYGO. Increase toward the expected system load and verify stability.
- With power off, install the LILYGO and verify +3V3 is supplied from the LILYGO header into the HAT.
Logic and CAN Bring-Up
- Verify +3V3 on U1 VIO, U2 VDD, U3 VIO, and pull-ups R1/R2.
- Program ESP32 GPIOs as specified: GPIO21 TWAI_TX, GPIO39 TWAI_RX, GPIO18 SPI_SCK, GPIO23 SPI_MOSI, GPIO19 SPI_MISO, GPIO32 CAN2_CS, GPIO34 CAN2_INT, GPIO22 LED_GPIO.
- Confirm LED_GPIO toggles LED1 through R3.
- For CAN1, verify TWAI_TX/TWAI_RX activity and CANH/CANL differential signaling.
- For CAN2, verify SPI communication with MCP2515 at 16MHz crystal operation, then verify MCP_TX/MCP_RX and CAN2_H/CAN2_L.
Key Probe Points
- +12V_RAW: J2 pin 16 / F1 input
- +12V_FUSED: F1 output / D2 anode
- +12V_PROT: D2 cathode / U4 VIN / D1 cathode
- +5V: L1 output / C10 / C8 / J1 +5V
- +3V3: J1 3V3 / U2 VDD / U1-U3 VIO
- CAN1_H/CAN1_L: U1 pins 7/6 and J2 pins 6/14
- CAN2_H/CAN2_L: U3 pins 7/6 and J2 placeholder pins 3/11
Open Verification Items
- Replace J2 with an exact OBD-II J1962 right-angle footprint/component before PCB layout or fabrication.
- Confirm exact LILYGO T-SIM7600G-H R2 header pin count and physical pin mapping against the module drawing before layout.
- Confirm MP1584 compensation/soft-start/frequency component values against the latest MPS datasheet and desired switching frequency/load transient target.