jamesbowman
commented
4 years ago Hi William,
Good questions. I'm going to improve the coverage of this topic in the manual,
I2CDriver is always USB-powered, so never draws power from the target circuit. For monitoring an existing circuit, it needs GND, SCL and SDA to be connected to it. You can optionally connect VCC to the circuit if you want I2CDriver to power it. In the case you mention of a VDD=5V circuit, the only connections are GND, SCL and SDA. The inputs to I2CDriver are 5V-safe, so electrically this is fine.
Hope this helps - I'm leaving this ticket open until the proper section in the user guide is written.
My understanding is that monitor mode allows us to monitor an i2c bus- which seems pretty cool.
I'm curious about wiring and voltages... and if I'm way off base on what I'm understanding so far. I thought I better ask a few questions before I start plugging things in!
For what I've used my board for so far- my computer has been the master and has been providing power to the attached devices.
Monitor mode sounds like there is and existing bus that we get to plug in to and listen in. That would mean another device is the master and power is coming from elsewhere. If true- does the i2cdriver draw power from the bus then? Can/should usb be connected without issue?
When connected to USB, i2cdriver produces 3.3v on the VDD pins. What if the bus to be monitored is using VDD=5v?