TTL Level - RS 232- Level ?

xl5 · Occasional Visitor Joined: Dec 08, 2004 Posts: 12

Hi
I have been having problems with a brodit pda mount and royaltek gps I was supplied with and have just got this answer from Royaltek.
Can anybody put this in simple terms for me as I do not have a clue about TTL/RS232.
Thanks in advance

Connection has been made using pin out from yourself and Brodit thus:
Royaltek red +, black-, tx yellow, rx white
Brodit red 6 +, black 3 - , tx 2 green , rx 4 yellow
The gps will not work with this configuration.
If the tx/rx are swapped over it still does not work.

Ans: Our GPS(RGM-2000MLP) output is TTL level and then through the car
adapter transform to RS-232 level to the device.
I think the Brodit PDA interface is RS-232 level , so even you
connect the right color but it still don't work , because the signal level
are different
between them.

2.Holux gps units as they have a ps2 plug as standard and work ok.(but our
gps need a ps2 + RS232)

Ans: Holux GPS maybe build up the RS-232 chipset in the GPS module,So ps2
connect only for data transmission and power.

Pc-Mobile · Posted: Sat Mar 05, 2005 4:54 am Post subject:

These mouse GPS all have different pin configurations so there is no standard. You ahve to obtain pin information from the maufacturer or their web site.

They should work if you bought as a package so they are guaranteed to work.
If you bought from different sources and they are not made for each you are bound to have problems.
A third party GPS mount should always accept RS232 level, not TTL.
If the PDA which the imount is for accept only TTL then the mount should change the incoming RS232 level from the GPS into TTL.
Unless it is supplied with the GPS as a package for a certain PDA (you did not say which) then there is a chance that the GPS/Mount/PDA all work through TTL.
Many mouse GPS output both TTL and RS232. If there is only one, it shouild be RS232. Unless as mentioned before, it is supplied as a package for certain PDA there is a chance that the GPS is TTL only.

If you bought the mount/GPS as a package you should return the mount, it is not functioning. I do not think the GPS is at fault.

If you are savaging the GPS cable and thinking it may work but do not know TTL from RS232, I suggest you stop there get a proper cable from Brodit. GPS car mount manufacturer should have cables available for most popular GPS, one is often supplied at the time you purchase the mount.
_________________
Pc-Mobile
http://pc-mobile.net/gps.htm

CTHindi · Occasional Visitor Joined: Jan 27, 2005 Posts: 33

I am not sure about RS232 Standards. However from what I remember (having worked with it a while back) is TTL ( Transistor - Transistor Logic ) Voltage < 0.8 V is definitely treated as 0. Voltage > 2.2 V is definitely 1 with some uncertain range in between. Other logic levels were CMOS Logic where these Voltage were different.

xl5 · Occasional Visitor Joined: Dec 08, 2004 Posts: 12

Thanks for the replies guys.
I think I have now worked out what is going on.
The royaltek gps ouputs a ttl signal to the car charger.
It is converted there to a rs232 signal and then onto the pda.
The brodit mount needs a rs232 signal to work so wiring the gps direct to the brodit mount will not work.
Something like a holux gps outputs rs232 as it is converted in the gps mouse so it will work ok.
I stand to be corrected as I am new to all this.
In my opinion my biggest problem started when I ordered the pda,gps and brodit mount and was told it is just a matter of chopping the plug off the gps and wiring it to the mount.

Pc-Mobile · Posted: Tue Mar 08, 2005 2:56 pm Post subject:

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