Hello,
I am trying to reverse use RPi-UEXT as it was ment in original design. I want to connect a module designed for the RPi on an OLinuXino A20 Board.
It seems to me that the RPi-UEXT can be used for that connecting the RPi module to the RPi-UEXT and the RPi-UEXT to the A20 using UEXT. I was hoping for a just plug-n-play, but:
The module uses I2C and only connects the pins 1 (3,3V), 2 (5V), 3 (SDA), 5 (SCL), 6 (GND) on the RPi header. According to the RPi-UEXT all signals should map to the UEXT connector, except 5V that is missing.
Has anybody a suggestion where to best get the 5V needed? Or why this should not work at all?
Thanks.
The UEXT on the A20 has 1-3,3V, 2-GND, 5-SCK, 6-SDA
All of the GPIO-x 40-pin connectors have +5V on pin 1
If you device requires 5V I2C, you may need dividers or level-shifters to chenge the 3,3V to 5V
The A20 schematic is on the WiKi
Be careful not to put any voltage more than about 3V into any pin on the A20. It is NOT a 5V-tolerant chip.
Level shifters should let you avoid that.
John
The module actually only needs 3,3 V I2C Signals. The 5V seems to be needed to power some of the components. I do not have any schematics on the module.
I have looked up a GPIO pin on the A20 with 5V in the schematics and took a look at the RPi-UEXT schematics, that the 5V connector on RPi-UEXT is only connected to the RPi connector pins 2 and 4 and has no connection back to the UEXT (I love Olimex for making the design files public).
So as far as I don´t accidently connect something wrong this should be fine (at least for testing purposes)? Just want to double check, not to burn my board.