LinkitOne and 8-Bit Level Shifter

Question

I want to connect LinkitOne with an LCD display requiring 5-volts in I/O. I opted for an 8-bit level shifter (TXB0108) from Adafruit to do this.

To start with, I made LinkitOne's 7 digital pins (D5-D11) as OUTPUT and DigitalWrite HIGH to each one and had consistently got 3.2 Volts. However, when I connected D5-D11 in the LOW-side of the level shifter and had the VCCA hooked at 3.3V and VCCB hooked at 5V, the low-side pins registered varying voltages below 3.2 volts (some are below 1v and 2v while only 2 pins are in 3.2 V.

I read in some sites that the 5V must be supplied from other source as the LinkitOne is not giving enough power for the level shifter. So, I did that... as well as with the 3.3 volts but still the problem persists.

Please kindly help.

Answer 1

I did a quick check if picking other I/O pins in LinkitOne will resolve the issue and it did. The pins that work with the 8-bit level shifter are pins D5,D6,D9,D10,D11,D12 and D13.

I went through the LinkitOne pinout diagram here, and the only unusual thing about pins D4,D7 and D8 is that they are labeled GPIO40, GPIO50 AND GPI048 respectively which is unusually above GPIO2X. I'm still new with this board and guess that these pins have some 'specific' functions as stated here.