Hardware

What WiCAN USB is made of: the screw terminal and how to wire it, where its power comes from, the USB port, the LEDs and the CAN controller behind them.

The screw terminal

The terminal has, in the order printed on the case, VIN, GND, CANL and CANH, and on earlier boards a fifth position, TR. The Pinout page shows the board and what goes where.

A CAN bus needs a 120 Ω resistor at each of its two ends. A vehicle bus has both already: tapping into it, for example through the OBD port, nothing is added. A bus you build yourself, or a single device on the bench, needs the termination. Boards with the TR position have the 120 Ω resistor inside, between TR and CANL: wiring TR to CANH switches it in. On a board with four positions, put a 120 Ω resistor across CANH and CANL at the end of the bus where WiCAN sits.

Tapping a car's OBD port

Pin 6 is CAN high, pin 14 CAN low, pins 4 and 5 ground and pin 16 the battery, which can feed Vin. The WiCAN OBD pinout shows them.

Power

WiCAN USB takes power from Vin or from the USB cable, and both can be connected at the same time; the USB side is diode protected. The Battery Voltage on the Status tab is the voltage on Vin: it reads near zero when only the USB cable powers WiCAN.

On a vehicle, Vin stays live while the engine is off. Sleep mode watches that voltage and puts WiCAN to sleep below a threshold you choose, see Sleep and battery alert. On a 24 V vehicle the voltage sits above the range of that threshold, so leave sleep mode off there.

The USB port

The mini USB port does two things: it powers the board, and it is a serial port at 4 Mbaud on which WiCAN talks slcan, RealDash or SavvyCAN frames like a wired CAN adapter, see USB serial. The same port is used to flash firmware for recovery.

The LEDs

The WiFi and data LEDs show through the case next to the terminal labels. LEDs says what each one means.

The CAN controller

Frames

CAN 2.0A (11-bit ids) and CAN 2.0B (29-bit ids), data and remote frames

Bit rates

5, 10, 20, 25, 50, 100, 125, 250, 500, 800 and 1000 kbit/s, chosen under Settings › CAN

Modes

Normal, or Silent for listening only: WiCAN then never transmits, not even the acknowledge bit, so it cannot disturb the bus

Termination

120 Ω inside on boards with the TR position, switched in by wiring TR to CANH; external on four-position boards

Hardware version

The About tab shows the hardware as WiCAN-USB. There is one hardware version (the board reads V110); it runs the usb firmware image, which also handles the 7.5 V to 36 V input range when it reads the voltage.