asked 2015-05-10 11:38:03 +0200
Hi Sailors!
I was looking for a small I2C expander for my Jolla, I want two I/O pins (1 as an input and 1 as an output) to control the Adafruit Powerboost 500. The goal is to build the PowerTOH.
Does somebody know a good small cheap I2C expander for Jolla (1.8V I2C)? Or a trick to use the I2C pins as input and output?
Cheers, Dylan
answered 2015-05-11 10:55:47 +0200
For prototyping get a BreadboardTOH or a MyHalf, makes life so much easier.
If you want to go straight for a one-off prototype with just as power circuit, consider:
Use the interrupt line as an input
Use the 3V3 line as an output
Put an extra USB port on your PowerTOH, charge via that. Signal on the interrupt line if the battery is full, hook the enable pin to the 3V3 line and if the phone needs power it just switches the 3V3 pin on. No need for I2C expander.]
If you need more help, let me know!
Well that's interesting! I only need to provide a voltage divider since the voltage levels aren't the same for the interrupt pin. I didn't know you can switch ON/OFF the 3.3V line... I'm familiar with the Arduino IDE and language, but with developing apps I still have to learn a lot.
Can you explain a little bit more how to use the GPO's in a Sailfish app
Dylan Van Assche ( 2015-05-11 18:30:57 +0200 )editAsked: 2015-05-10 11:38:03 +0200
Seen: 437 times
Last updated: May 11 '15
you can use a logic level converter to switch it to 3.3v i2c, which makes it a bit easier to use with the 3.3v supply pins from the jolla.
r0kk3rz ( 2015-05-10 11:55:47 +0200 )editThat's true but I would like to use only one IC to make very small and easy to build.
Dylan Van Assche ( 2015-05-10 12:02:25 +0200 )editalso, you can use the interrupt pin as GPO, which gets you one pin at least
r0kk3rz ( 2015-05-10 12:06:46 +0200 )editThe thing is that the Powerboost from Adafruit has an enable pin (activate charging or not) and a low battery pin which will be pulled to GND when the battery is under 3.2V
Dylan Van Assche ( 2015-05-10 12:33:11 +0200 )editIf I can use the interrupt pin as an output then I found a solution to build it with only one output pin.
Dylan Van Assche ( 2015-05-10 15:54:48 +0200 )edit