Roger_Allen
Posts: 4
Joined: Fri Sep 03, 2021 7:17 pm

Pi 4 / Arduino Due / MCP4725 I2C Question

Thu Oct 14, 2021 5:55 pm

I am communicating between a Pi 4, Arduino Due, & BME280 using I2C - VCC is 3.3V
The issue is that I have to add a MCP4725 DAC and the output must be 0-5V
My question is. With the rest of the I2C all running at 3.3V do I risk breaking or damaging anything if I connect a 5V VCC to the MCP4725?

I tried adding a bi directional level shifter before the MCP4725 but it put a lot of noise on the the DAC 0-5V output.
Any advice would be appreciated.

aBUGSworstnightmare
Posts: 3610
Joined: Tue Jun 30, 2015 1:35 pm

Re: Pi 4 / Arduino Due / MCP4725 I2C Question

Fri Oct 15, 2021 5:51 am

Roger_Allen wrote:
Thu Oct 14, 2021 5:55 pm
I am communicating between a Pi 4, Arduino Due, & BME280 using I2C - VCC is 3.3V
The issue is that I have to add a MCP4725 DAC and the output must be 0-5V
My question is. With the rest of the I2C all running at 3.3V do I risk breaking or damaging anything if I connect a 5V VCC to the MCP4725?

I tried adding a bi directional level shifter before the MCP4725 but it put a lot of noise on the the DAC 0-5V output.
Any advice would be appreciated.
how can your leel shifter add noise to your DAC output? What have you implemented? Have you check your 5V supply rail for noise?

Roger_Allen
Posts: 4
Joined: Fri Sep 03, 2021 7:17 pm

Re: Pi 4 / Arduino Due / MCP4725 I2C Question

Fri Oct 15, 2021 1:01 pm

The DAC is driving a 0-5V proportional valve. When the 5V VCC (from The Pi) is connected directly to the McP4725 DAC the valve behaves as expected. When the level shifter is added between the pi and the DAC and the exact same 5V connection is used on the Hi side of the level shifter the valve becomes unstable

Brandon92
Posts: 949
Joined: Wed Jul 25, 2018 9:29 pm
Location: The Netherlands

Re: Pi 4 / Arduino Due / MCP4725 I2C Question

Fri Oct 15, 2021 1:07 pm

Can you give us a diagram of how you connected everything together

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