osbock
Posts: 19
Joined: Fri Jun 08, 2012 1:07 pm

Uart pin type question

Fri Jun 08, 2012 1:16 pm

Hi,
I'm helping design an Arduino-ish add on board, and am trying to select a level shifter to make it safe to talk to the Pi.
I'm considering using some devices from TI similar to this:
http://www.ti.com/product/txb0104
and they come in two types:
Can you figure out which device (TXB series or TXS series) we need for the UART Serial comm (below) ?

TXB Series
Where "B" indicates buffered-type. Designed to exclusively be connected and interfaced with a push-pull CMOS driver and is capable of driving a capacitive or high impedance loads in applications such as Secure Digital (SD) or Serial Peripheral Interface (SPI). The TXB010x devices are not intended for use in open-drain applications.

TXS Series
Where the "S" indicates switch-type. Designed to interface with open-drain drivers and can be used in applications such as I2C.

mharizanov
Posts: 19
Joined: Thu May 31, 2012 12:57 pm

Re: Uart pin type question

Fri Jun 08, 2012 7:16 pm

I have an Attiny84 (3.3V) talkig both ways directly to the Pi over UART via the NewSoftSerial library, no level shifting, works pretty straight forward. Would that help?

osbock
Posts: 19
Joined: Fri Jun 08, 2012 1:07 pm

Re: Uart pin type question

Sat Jun 09, 2012 11:56 am

No, we're trying to keep the Arduino part as standard as possible, and since a lot of shields use 5V, and the rating for 16Mhz is 5V we need to shift.

User avatar
rew
Posts: 425
Joined: Fri Aug 26, 2011 3:25 pm

Re: Uart pin type question

Sat Jun 09, 2012 7:44 pm

One:
use a resistor and a scottkey diode to 3V3 on the line going into the 'pi. Simple, cheap.

Two, you need the buffer (B) version, not the switch (s) version.
Check out our raspberry pi addons: https://www.bitwizard.nl/shop/

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