A CANBus Tiny Network without transceiver Ics:stm32f4 Discovery

Sometimes you have a can equipped processor in a low cost board but it has no CAN transceiver chips.

Here is a method, the can be used to create a small experimental network with such a board.

There'll is no noise immunity and you might has to lower the speed ....

But many experimenters has made this work satisfactorily.

Use a signal diode similar to 1n914 or 1N4148.

Power supply diodes usually do not has a fast enough recovery time for CAN to function.

Modifying the STM32F4 Discovery:

In order to connect the both CAN controllers together, you must add signal diodes (1n914, 1N4148 or similar)

And one 3.3 K? Resistor as shown on this schematic.

The connections is easily accessible.

1. Add the three parts as shown on the schematic and in the photo.

2. Connect the resistor to the 3 volt supply as shown.

3. Add a jumper wire (not shown) from PB5 to PB8.

4. Note:i used a 2.7K? Resistor and it seems to work well.

5. I soldered the components to the board.

6. Note:you'll need to open the resistor for a step later.

You cannot connect the-a real CAN network as the voltages is wrong and it's not differential.

It's suitable for small experiments.

Tip:to View CAN frames on a oscilloscope:connect to the low side of the resistor. This would give a clean waveform.

A CANBus Tiny Network without transceiver Ics:stm32f4 Discovery