I thought the OP was interested about connecting a GPS module with 5V TTL
interface to the internal serial port of a TS-xxx that is directly tied to
the processor, not the external, RS-232 level compatible DB9 connector.
That is what my message referred to. Of course, if you want to interface to
a true RS-232 interface, it's a different problem and you do need some
level conversion if for no other reason than you also need inversion.
Typical RS-232 driver chips invert the signal.
However, if you want to get timing and position data from a GPS receiver,
you only need the Tx data from the GPS into the Rx data of the processor,
so there should be no issue with frying the GPS module. More specifically
if you want to get a 5V TTL signal into an RS-232 input, you can probably
get by with a simple CMOS inverter gate or an NPN transistor with two
resistors, powered from the TS-xxxx 3.3V supply. All RS-232 driver chips
made in the last 10 years actually will work with TTL levels on the input,
keeping in mind that the signal needs inversion.
Didier
On Fri, Feb 28, 2014 at 4:43 PM, Jim Jackson <> wrote:
>
>
>
>
> On Fri, 28 Feb 2014, Didier Juges wrote:
>
> > Be careful that some GPS modules output 5V TTL. That will fry rour
> TS-xxxx
> > in a hurry. I know that for a fact.
>
> Or vice-versa - the true RS232 outputs from the TS7200 will fry the GPS
> interface :-(. I don't think the TTL inputs like negative voltages applied!
>
> The TS7200 outputs voltage in the RS232 voltage ranges - I believe, if
> memory serves, it was a fair while ago, the output voltage levels are -5v
> and +5v. There is also the problem that rs232 levels are "inverted"
> compared with TTL levels.
>
> You do need some form level conversion. The TS7200 input will need
> RS232 input voltages - so you HAVE to have something to generate the
> negative voltage. There are fairly simple transistor/capacitor/resistor
> solutions see...
>
> http://picprojects.org.uk/projects/simpleSIO/ssio.htm
> http://www.uchobby.com/index.php/2007/06/11/ttl-to-rs232-adaptor-explained/
>
> I've made them and they usually work ok. But using a max3232/max232 is
> more guaranteed.
>
>
> > You do not need RS-232 level shifters, but you may need one to go from 5V
> > to 3.3V. Usually, a 4.7k resistor in series with the Tx output of the GPS
> > is all you need. The input of the TS-xxxx will clamp at 3.3V and the
> > resistor will limit the current to a safe value. No need to do anything
> > with the Tx output of the TS-xxxx. The 5V device will accept 3.3V inputs
> > just fine.
>
> What you say pertains to interfaces 3.3v systems to 5v systems.
> Interfaces either 3.3v or 5v TTL systems to true rs232 is a completely
> different thing.
>
> Jim
>
>
> >
> > Didier
> >
> >
> > On Fri, Feb 28, 2014 at 9:46 AM, Jonathan Leslie <
> >wrote:
> >
> > >
> > >
> > > I dont' know the ts7200 specifically, but the ts7500 you just solder
> onto
> > > the RX and GND pins to the gps modules TX and GND pins and you are
> hardware
> > > ready to go. The GPS module broadcasts 1 a second a dump at 4800 BPS.
> > >
> > >
> > >
> > >
> > >
> > >
> > > ------------------------------
> > > *From:* Yan Seiner <>
> > > *To:*
> > > *Sent:* Friday, February 28, 2014 10:40 AM
> > > *Subject:* [ts-7000] TTL serial on a TS7200
>
> > >
> > >
> > > I have a TS7200 that I'd like to interface with a GPS module. Most of
> > > the bare modules are TTL - 3.3 to 5V. Is there a way to set up a serial
> > > port on the 7200 with ttl levels?
> > >
> > > I need RX, TX, and DCD pins active on the serial port for the GPS.
> > >
> > >
> > >
> > >
> >
>
>
>
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