Hardware Reference

MDB — Middle Driver Board

The main vehicle controller. Talks to the ECU over CAN, reads keycards and batteries via NFC, and manages cellular/GPS connectivity.

nRF52840 Co-processor

The nRF52840 handles Bluetooth Low Energy and LED control. It communicates with the MDB via a USOCK protocol (UART framing with CBOR encoding). The bluetooth-service on the MDB owns this interface and exposes BLE state to Redis.

Blinker and hazard switch

The stock handlebar switch has two blinker positions, wired to separate GPIO inputs on the MDB. Some aftermarket switch assemblies add a physical hazard button that closes both inputs at once.

Since 1.2, vehicle-service recognises that: when both blinker inputs are active it reports blinker:switch as both and runs the hazard lights. Stock switches behave exactly as before, so this costs nothing if you haven't swapped yours.

DBC — Dashboard Computer

Runs the dashboard UI (Qt on a 480×480 display) and offline navigation.

Display pipeline

The IPU (Image Processing Unit) drives the parallel display via /dev/fb0. The GPU renders to an EGL surface using the render node (/dev/dri/renderD128) and blits to the framebuffer. The GPU and display are separate subsystems; etnaviv has no KMS connectors.

Network Topology

The MDB and DBC are connected via USB Ethernet gadget. The MDB runs a Redis instance; DBC services connect to it over the network.

From an external machine, SSH into the MDB first, then jump to the DBC:

ssh root@<mdb-ip>               # MDB direct
ssh -J root@<mdb-ip> root@192.168.7.2  # DBC via jump

UART Debug Access

Both boards expose a 3-pin UART debug header at 115200 baud, 8N1. No hardware flow control.

Boot Flow

MDB Boot Sequence

1. U-Boot loads from eMMC boot partition
2. Kernel decompresses and initializes hardware
3. systemd starts services in dependency order
4. vehicle-service enters stand-by state, scooter is ready for keycard

DBC Boot Sequence

1. U-Boot (stored in eMMC boot partition, mmcblk3boot0) loads kernel and DTB from /boot/ on the active rootfs partition
2. Kernel initializes i.MX6DL, IPU, and etnaviv GPU
3. Boot animation starts early (~T+3s), rendered by ThorVG to /dev/fb0, runs until multi-user.target
4. scootui-qt Qt dashboard starts via dbc-dispatcher
5. The /data partition (mmcblk3p4) mounts at ~T+7s after fsck, so it's not available for early services

Mender A/B Partitions

Both boards use Mender for OTA updates with atomic A/B partition switching. The active partition is selected by U-Boot on each boot. A failed update automatically rolls back to the previous partition on the next boot attempt.