Replacing T2.0 with LC, voltage question

M

Magnethead494

Well-known member
I designed the PCBs for my project around the 2.0, which i'm aware is going away (sooner than I thought). It's interfacing an ADS1115 and a 3rd-party 5-volt UART device.

I am only using 6 pins on the 2.0: Vcc, Gnd, TX1, RX1, SDA, SCL

The UART header only has TX, RX, and Ground

The ADS1115 has VCC, Gnd, SDA, SCL

To swap the LC into the same footprint, I need to know what to change.

RX/TX2 are in the same place as RX/TX on the 2.0, so I think i'm okay there. But what do I need to change for the voltage issue?

SDA/SCL are across the board. I can simply not solder in the RX/TX3 pins and solder in wire jumpers, but what do I need to change for the voltage issue? The major issue is that the ADS1115 is reading in 0-5 analog signals from 3rd party devices, so I can't drop it to 3v3 VCC levels.

What's my best options? What can I add if I make a PCB revision to solve the voltage issues?

Teensy is USB powered, so Vcc is Vusb

Screen Shot 2022-06-19 at 5.10.45 PM.png
 
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There are voltage level converters that can handle bi-directional conversion issues for I2C (RX/TX are unidirectional, so they should work ok with just about any logic level shifter). These are available at various places, including:


I have used the pololu level shifter back in the day when I still had 5v i2c devices. I have not used the Sparkfun shifter. Adafruit also has a bi-drectional level shifter, but there is a note that says it doesn't work too well for I2C.

For the i2c bus, you want to put all of the 5v devices on one side of the shifter, and 3.3v devices on the other side.
 
MichaelMeissner said:
There are voltage level converters that can handle bi-directional conversion issues for I2C (RX/TX are unidirectional, so they should work ok with just about any logic level shifter). These are available at various places, including:


I have used the pololu level shifter back in the day when I still had 5v i2c devices. I have not used the Sparkfun shifter. Adafruit also has a bi-drectional level shifter, but there is a note that says it doesn't work too well for I2C.

For the i2c bus, you want to put all of the 5v devices on one side of the shifter, and 3.3v devices on the other side.
Click to expand...

I'd used an older/larger converter design and was hoping to avoid going that route. But that pololu looks small enough to fit on my board without too much pain. Thanks!

Gonna suck not being able to use the boards I already have, but oh well. I was hoping the 2.0 supply would last another 6 months when this project will be complete.
 
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