Hi,
I am working on a project where i need to interface with my DAC through I2C pull up by 3.3V, through various forums, I came to conclusion that I cannot use Arduino UNO to interface with my DAC as it high level logic voltage is 3.5V, simple solution to the problem is to use level translator. But It will be better if I use a controller which works with I2C 3.3V logic. Any suggestion on the board is appreciated.
Thanks in advance.
It is 5V on Uno.
Pro Micro 3.3V
Pro Mini 3.3V (you will need a USB-serial adapter for programming)
An ESP8266 or ESP32 would meet the requirement
Sorry 3.3V is the minimum high level logic from the datasheet (0.7VCC=0.75=3.5V).
Thanks for the suggestion.
There are many 3.3V boards and even more 3.3V microcontrollers. In fact, the 5V Arduinos are more of an exception than the rule...
ESP-boards are 3.3V
STM32 boards are 3.3V
Several of the more modern/recent Arduino boards are 3.3V (just click on any Arduino board on this page https://www.arduino.cc/en/Main/Products and look under tech specs)
Indeed, and as far as I can tell from your question there's no reason why this solution wouldn't work...
That's the safe level, typically applicable to output pins. See the input pin voltage diagrams that start HIGH at about 2.6V for 5V Vcc, including hysteresis (0.05*Vcc=0.25V around Vcc/2=2.5V).
Thanks for your reply.
I know the solution works but it adds extra space and component.
Actually i am validating a circuit board (Used for Automotive application) which actually has some processor interface to the DAC and couple of other circuits too, but i am trying to validate the board without the use of processor i.e with other controller externally. Adding a level translator to the controller adds extra component.
Also Arduino DUE is a 3.3V logic device.
Which is means I can use arduino uno to dac with 3.3v pullups?
Yes; a number of people have reported that this work fine.
Also in long run, it affects the life span or damage the device right?
If it has to be an UNO, then you could carry out a modification like this:
I've used something very similar on a clone UNO.
If this needs to be qualified for automotive use I think most Arduino boards are not an option as they aren't qualified for this application. They may have a few types that are, but I never dived into it. Forget about the regular consumer boards in any case if this is a serious commercial application.
Does the board Pro Micro 3.3V, Pro Mini 3.3V has 3.3v logic (for high) at their i2c pin ?
Yeah of course
yeah sure! also i am not validating the whole board, just validation is going to be done on particular circuit (validate a specific ic in my case) on the board.
Also thanks for your suggestions and solutions.
Ok, I get it; in that case requirements aren't very strict on the board. Basically any board in which the microcontroller runs on 3.3V you could assume the logic high on I2C to be 3.3V.
Of course in fact it's a little different, since on I2C neither master nor slave ever writes a HIGH level to either of the lines. The high level is just the level to which both lines are pulled up with external pullup resistors. Due to the limitations of voltages on digital pins combined with the voltage needed to be read reliably as HIGH, it's customary at least on the microcontroller side to pull up I2C lines to the Vcc of the microcontroller. On I2C slave devices the situation is often different, with their I2C pins being often (but not always!) tolerant to higher levels than the supply voltage of the chip itself.
So remember this: in I2C, a HIGH level is never actively written by either master or slave. The HIGH level is only constituted by the rail the pullup-resistors connect to.
yeah got it, thanks!
In my case, i actually have a pull up resistor between my processor and DAC with 3.3V, since i am not using the processor looking for other controllers to externally interface with I2C line of the DAC (which actually have pullup resistor), wants to make sure its logic level is sufficient enough to communicate.
Now I understood the fact!