Cerbuino Bee I2C on Arduino-compatible pins?

Does the Cerbuino Bee support I2C on analog 4 and 5 Arduino-compatible pins?
The wiki doesn’t mention it: GHI Electronics – Where Hardware Meets Software

There is built in software i2c that works on any pins including the ones you need.


bee ref schematic

If your Arduino shield uses these pins for I2C, double-check that it’s using 3.3V I2C and not 5V I2C.

With FEZ Cerbuino Bee, pin A5 is not 5V tolerant (in either analog or digital mode). As with Arduino Pro 3.3V, you’ll need to modify your shields to drop the voltage of some pins.

Most of the other pins on FEZ Cerbuino Bee are 5V tolerant. A possible workaround is to cut the tail off of pin A5 on your shield and route a wire between A5 and another pin (and use software I2C).


Why are you saying that pin is not 5V tolerant? If I remember correctly, all pins are 5V tolerant except reset.

Hi Gus,

Microcontroller pin A4 (DAC1) is a 3.3V only pin, and is not 5V tolerant.

Pin header A5 on FEZ Cerbuino Bee is connected to microcontroller pin A4.

STM32F405 datasheet:

Page 1:
“Up to 140 I/O ports with interrupt capability. Up to 138 5 V-tolerant I/Os.”
As with STM32F205, the 2 I/Os which are not 5V tolerant are the two DAC pins.

Page 43 and 47:
On page 47, A4 is categorized as “TC”. Page 43 lists “TC” as “Standard 3.3V I/O”. 5V tolerant I/Os are categorized as “FT”.

Page 70:
Absolute maximum allowable input voltage on non-five-volt tolerant pins is 4.0V. Exceeding this voltage can cause permanent damage to the device.

The phrasing “up to” on page 1 also has some interesting connotations. Full details are in the datasheet.


1 Like

@ Chris Walker - good info.

Thanks, Chris. That’s quite important information.

Sorry but I’m coming from the Arduino/Netduino world.
Based on your little tip, I found the GHI.OSHW.Hardware.SoftwareI2CBus class.