I have several devices on the I2C bus:
All devices are powered by 3.3V. The voltage on the I2C bus is 5V.
Question: Is the voltage difference on the bus and device power normal?
3
-
3It's better to use level translator. Or you can try to power pull-ups from 3.3V, it usually works, but 3.3V CMOS output interfacing 5V CMOS logic input isn't 100% compatible as some devices might need almost 3.5V to detect high level.– KIIVCommented Feb 21, 2020 at 9:02
-
KIIV, Thank you for the help!– DeltaCommented Feb 21, 2020 at 9:20
-
1Are you using the bare chips, or do you have breakout board. If the latter, the problem might be with Arduino enabling the internal pull-up resistors inside the MCU. The breakouts already have pull-up resistors on them, so the Arduino board shouldn't do that (but does). Usually it doesn't matter, and help with people using bare chips, and forgetting to add pull-up resistors on the I2C lines. To disable them; see arduino.stackexchange.com/questions/13448/… . After that the I2C lines should read 3.3V instead of 5V.– GerbenCommented Feb 21, 2020 at 14:39
Add a comment
|
1 Answer
There are 3.3V devices that have 5V-tolerant inputs; that may be the case for your devices, but I would not risk it. Use a level converter designed for I2C, such as https://www.adafruit.com/product/757. Or you can make your own; https://cdn-shop.adafruit.com/datasheets/an97055.pdf explains how such a level converter works. Use a BSS138 if you are comfortable with soldering SMT components; otherwise use a 2N7000.
-
-
For the DS3231 the maximum voltage if
Vcc+0.3V. The TMP100 seems to allow up to6Vregardless of Vcc. The 24L256's maximum isVcc+1.0V– GerbenCommented Feb 21, 2020 at 14:34