I am trying to do 2 different things:
On ttyAM0 I want to be able to run a console that connects the TTL to rs232. I
have a couple of MAX233 chips on hand but they are for 5V to rs232. I am
concerned about driving the TS7400 serial port pin to 5V since I believe it is
limited to 3.3V. For this I am just going to order the 3.3V version of the MAX
chip (MAX3232).
The second thing I want to do is on ttyAM1 I want to connect the TS7400 which
is 3.3v to another 5v device. I really would like to avoid the long chain of:
TS7400 <-> MAX3232 <-> MAX233 <-> 5V device
Sending 3.3v to the 5v device is not a problem as that is enough to trigger the
logic on the 5v device. The problem is the 5V device sending a signal to the
3.3v TX7400. I am wondering if for 5V -> 3.3V if just adding a current
limiting resistor would suffice in keeping the board safe?
- Doug
----- Original Message ----
From: evil666demonic <>
To:
Sent: Tuesday, March 18, 2008 1:09:32 PM
Subject: [ts-7000] Re: TS7400 serial ports - 5V or 3.3V?
I use a TS-7260 to talk to a couple UART devices. I use the MAX232
chip to translate between the com ports on the 7260 and the TTL level
UART on my external devices. Is this what you are trying to do (as
opposed to the TS-7400 being your TTL side, and something else is the
rs-232)? If so, it works fine for me. If you have any trouble, I can
provide you schematics for various translations I have used in the past.
-Terrance
--- In Doug Chapman <> wrote:
>
> I just got my TS7400 today, (it was rush ordered because I just
fried my 7250, very sad). I am rushing to get a robot ready for the
Trinity College competition in a few weeks.
>
> I was just about to pull out my MAX233 chip out of the drawer to
hook up a TTL - RS232 converter. Before I do are these pins 5V
tolerant or are they limited to 3.3V. I searched for posts and found
some discussions but nothing authoritative. From the MAX233 spec
sheet it appears this chip is 5V only.
>
> I also plan on having the second serial port communicate with an
other 5V serial device. If the 7400 is limited to 3.3v does anybody
have a suggestion for a 3.3V - 5V serial translator?
>
>
> thanks,
>
> - Doug
>
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