Electrical Specs

Andrei Railean

Hi Guys, are there any electrical and clock specifications for docks, expansions and the omega itself?
I'm interested in typical voltage and allowed ranges on GPIO and i2c pins.
As there are 4 different voltage headers on the expansion (1.8, 2, 3.3, 5) it'd be good to know what voltages are used to communicate to other expansions.

Knowing tolerance ranges is helpful to know what external peripherals can be hooked up and what extra circuitry may be needed to support them.

I don't have an oscilloscope to measure any of this.

Zheng Han

@Andrei-Railean the logic voltage on omega gpio pins are 2.5v +- 10% and the rated current draw is 24mA. It is recommended to use a voltage divider or level shifter when working with 3.3v and 5v devices.

With personal experience, I have connected omega directly with 3.3v I2C devices without seeing any issues.

Andrei Railean

Thanks @Zheng-Han

Frederic Baumann

Hi,

it looks like these values are for output GPIOs, but what about levels for INPUT GPIOs, especially:

what is the maximum allowed voltage on an input GPIO?
what is the minimum voltage to get a logical 1 on a GPIO?

Thanks in advance!

Kit Bishop

@Frederic-Baumann Yup! Good questions. In fact in more detail what we need to know:

Maximum tolerated voltage on GPIO input - i.e. voltage above which one is likely to do damage
Minimum voltage on GPIO input for a logical 1
Maximum voltage on GPIO input for logical 0
Expected current sink for GPIO input when a logical 1 for a given/typical input voltage
Expected current sink for GPIO input when a logical 0 for a given/typical input voltage
Typical current supplied for GPIO output when a logical 1 with typical output voltage
Typical current supplied for GPIO output when a logical 0 with typical output voltage

Frederic Baumann

Yes indeed. Personally, I will be happy with the 3 first values as a first answer

Lazar Demin

As Zheng mentioned above, the logic voltage is 2.5V +/- 10%, so

Minimum voltage on GPIO input for a logical 1:
- around 2.5V
Maximum voltage on GPIO input for logical 0:
- around 2.25V
Maximum tolerated voltage on GPIO input:
- Don't know for sure, but I've connected 5V before with no problems

We'll do some further testing and research, and we'll put up a wiki page on this topic!

Frederic Baumann

Thanks! Good news for the 5V, meaning no special adjustement is required for 5V logic.

Brian Piersel

I found a datasheet for the AR9331. The specs on the GPIO are lacking detail, but I did find the following:

VOH = 2.44 V
VOL = 0.1 V
VIH = 0.7 V
VIL = 0.3 V
(These are min/max values as appropriate.)

I'm not finding a maximum voltage for the GPIO pins. The datasheet I found is a preliminary from December 2010. I'm hoping a newer datasheet is available that has more complete electrical info.