On Sat, Mar 14, 2009 at 4:45 PM, teohoeeng <> wrote:
> Yes, I want to interface between 3.3V TTL UART and 5V TTL UART without using
> any RS232 shifter to reduce hardware parts. I am only concern with 3 lines,
> TX, RX and GND.
>
> In fact, my 5V TTL sensor can receive data possibly because the 3.3V logic
> output still meet 5V TTL input requirements, but not the other way round,
> that's why I cannot receive the data out from 5V sensor output into the
> TS7800 3.3V TTL UART. I think I just need to meddle with this RX line and
> leave the TX line untouched. I am reading my old digital system notes now ot
> review those Voh, Vih, Ioh, Iih which I have to use to size up the interface
> circuits or resistor....
>
> I also read in maxim website that simple resitor voltage divider with diode
> can help to do that...but I just want to verify by calculting if the
> resistors used will be compatible to my interface...
>
> I believ there are some standard resistance values to use for 3.3V TTL to 5V
> TTL serial interface to use...I am checking and trying to calculate now....
I've used a MAX3100E (a bi-directional level shifter) to interface a
2.8V gsm modem uart to 3.3V lpc2378 uart. The gsm modem was not 3.3v
tolerant. The MAX300X devices have a 1.2V - 5.5V range on VL and 1.65V
- 5.5V VCC range. Should easily work for your application.
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3672
Ted Roth
------------------------------------
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/ts-7000/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/ts-7000/join
(Yahoo! ID required)
<*> To change settings via email:
<*> To unsubscribe from this group, send an email to:
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
|