Adding Resources to the Concept Car
Regarding Upgrades of the ConceptCar
The Concept Car has a modular architecture allowing the addition of resources in a simple way. In order to integrate a new ECU into the ConceptCar, these things are important:
- It is attached to the CAN bus, but does not disturb the regular operation of the car. This means that no already used CAN IDs may be overwritten and that the bus load has to be low enough.
- It fits the form factor of the ECU stacks on the ConceptCar, so it can be easily and properly mounted.
- It does not interfere with the ConceptCar's power train, especially does not short circuit the galvanic isolation.
Apart from that, new ECUs may interfere with whichever sensor or actor equipment should be mounted to the car.
This page illustrates the demands regarding the form factor of the small boards so they can fit into the ECU stacks. There they are well mounted and protected against physical damage by the massive metal box next to them.
All boards featuring an AT90CAN128 microcontroller are supposed to fit into any of the 8 spaces at the CAN bus box. Therefore they share the same dimensions, drill holes for mounting and SUB-D jack position. They all have the same dimensions to be interchangeable in place.
This dimensions are precisely the same used for the SensorBoards in the old Hardware Revision 1.0, all Revisions >= 1.2 must comply with these dimensions.
Since the boards can be stacked, it is a good idea to place all connectors, switches and LEDs near the borders.
Figure 4.1 presents the board dimensions.
First apply this in the schematic:
- Add the 4 drill holes as parts MOUNT-HOLE3.0
- The SUB-D CAN connector must be of type F09H
To get a proper board, follow these steps in eagle (when starting from scratch):
- Set the grid to 1mm
- Move the edges of the dimension polygon so that it's a square of 73mm x 73mm, with its origin being in the bottom left edge.
- Move the drill holes to the positions 4mm apart from each edge
- Rotate the SUB-D CAN connector to face upwards and move it to position 37.506mm/60.88mm. MOVE CAN_BUS (37.506mm 60.88mm) would do this.
These are recommendations on what operational controls to use to supply a uniform look&feel (and in some aspects programming) of the sensor- and actor-boards. The placement is not critical, it just looks better this way.
- The CAN bus driver is designed to signal the bus state with 2 LEDs (a green one for error active state and a red one for bus off state). Those LEDs are attached to I/O-Pins PA7 (red LED) and PA6 (green LED), over a resistor of 220 Ohms to ground each. The LEDs (package: CHIP-LED0805) should be placed as in the list below
- A green power on LED (CHIP-LED0805) that is directly attached to the power supply is recommended.
- If any additional LEDs are required, they should be placed at the lower border, like the CAN LEDs 200mil away from it or like in the list below.
- Connectors to peripherals or other boards must be low enough to avoid trouble with other boards in the stack. Recommended type is for example L02P, L03P, L05P.
Reset Switch: 550x275; C 100n: 865x 415; R 10k: 865x335;
LEDS: Power: Resistor (220 Ohms): 865x255; LED: 65x175
LEDs with Resistors from left to rigt: R: 1075x25; LED: 1075x175; R: 1230x255; LED: 1230x175; R: 1550x255; R: 1800x255; R: 2025x255; R: 2225x255;
Diode BAS85: 2375x2745
Diode Minimelf: 2440x2430, angle 270°
Coil: 2215x2655, angle: 270°
MAX1837: 2365x2630, angle: 90°
Capacitor: 2595x2435, angle 270°
AT90CAN128: 1825x840, angle 270° (not forced)
ISP is mandatory, but JTAG can be omitted.
AT90CAN128 Pin Connections