---
active: true
derived: false
header: 'EPB ECU'
level: 1.1
normative: true
reviewed: null
links:
  - SYS-001
  - SYS-002
  - SYS-003
  - SYS-004
  - SYS-005
  - SYS-006
  - SYS-007
  - SYS-008
  - SYS-009
  - SYS-010
asil: D
---

# SA-001: EPB ECU

## Responsibility

Central control unit of the electric parking brake. Contains all
software components and the electronic actuation of the actuators.

## System context

```plantuml
@startuml
node "EPB ECU" as ECU
node "Actuator left" as AL
node "Actuator right" as AR
node "Wheel-speed sensors (x4)" as WS
node "Inclinometer" as IN
node "EPB switch + LED" as SW
node "CAN bus" as CAN
node "Instrument cluster" as DI
node "OBD tester" as OBD

ECU --> AL : PWM, I-meas
ECU --> AR : PWM, I-meas
WS --> ECU : pulses
IN --> ECU : SPI
SW --> ECU : GPIO
ECU --> SW : LED
ECU <-> CAN
CAN <-> DI
CAN <-> OBD
@enduml
```

## Interfaces

| Interface     | Type             | Direction |
|---------------|------------------|-----------|
| Actuator L/R  | PWM + shunt      | I/O       |
| Wheel speed   | Hall pulses      | in        |
| Inclinometer  | SPI              | in        |
| Switch        | GPIO debounced   | in        |
| LED           | GPIO             | out       |
| CAN           | ISO 11898        | I/O       |

## Subcomponents (allocated to software)

Realised in software: all SWA elements SWA-001..SWA-010.

## Non-functional properties

- Worst-case reaction time (switch to actuator motion): 250 ms
- Flash demand: < 256 KB
- RAM demand: < 32 KB
- Current: < 200 mA (standby) / < 30 A (actuator peak)