FEZ Mini SERIAL DEBUG

NETMF & Gadgeteer
1

Hi
Two questions about the Mode pin on the FEZ mini board. I’m trying to use COM1 as the debug port to free up the USB port.

It appears the MODE pin needs to be grounded to do this. On the FEZ Mini board, this pin has a 330 ohm resistor connected to the RED LED tied to ground. The MODE pin drives the RED led on the board - used in the demo projects.

Is it correct to solder a jumper wire between this pin and ground to make COM1 the debug port - thus making the RED LED useless (unless I add another green wire jumper and cut the trace).

And on this page - GHI Electronics – Where Hardware Meets Software - it says "Remember that once you connect the pin high or low then you can no longer use it in your application. For example, the MODE pin on FEZ Domino is the same pin used for LED and it is also a PWM pin. Once you short the pin to ground (through the jumper), you should never attempt to use this pin, never try to use the LED or you may damage your device! "

Yet in the USBizi user manual, it says “Note: BL (IO0) and MODE (IO4) pins can still be used from managed code after USBizi firmware boots up.”

So which is correct - do I need to make sure I don’t have code using the MODE bin after boot?

Are there any other settings I need to watch - I’ve seen issues with RX pin but not sure they apply to FEZ mini.

Thanks so much.

2

You can use a 10K resistor to make MODE low and then it can be used by your application.

3

Thanks for fast reply.

Just to confirm, once I solder in this 10K jumper on the Mode pin, I should be able to debug using COM1 and the USB-Serial cable that came with the FezMini Evaluation board.

And if I want, I could just remove the LED and put a 10K chip resistor in its place - thus having a 10,330 jumper to ground.

4

Yes