Electron I2C Voltage Compatibility Question

General
1

Quick Question:

I am working on a project for Electron that needs to talk to external MCU’s (Arduino). I am thinking on using I2C since distance is less than 50 cm between devices and it is convenient to share the same line in the bus for all my external devices needs.

I have this two questions:

  1. I see that I need external pull up resistors on the SCL SDL lines… Since the arduinos I need to talk to are 5VDC and this board does not have 5VDC regulated supply (Only 3v3)… Can I use the Li+ battery as the source for the pull ups or would I burn something? or am I stuck with 3V logic? I know the electron is 5V tolerant… But the Li+ pin can supply more voltage My application battery is 6VDC [Maybe that’s enough to smoke something].

Also possible (not for this application but you never know!) what happens when someone hooks say 7V… Or the battery starts fluctuating… I don’t understand that much the side effects.

Also to note that all devices will be powered from the same battery source.

  1. How many devices is it ok to have in the network? I need to poll them every 10 second so traffic is not an issue.

  2. Any other suggestions? I am attaching a picture of the bus, missing the pullups for now…

Screen Shot 2017-10-25 at 11.29.29 PM.png1404×592 21.8 KB

Screen Shot 2017-10-25 at 11.30.00 PM.png862×652 39.1 KB

2

  1. If you want to talk to a 5V Arduino let the Arduino side do the pulling-up

  2. I2C allows 127 individual addresses for read/write access

1 Like
3

Sounds like a good idea. Thank you!