LVTTL to RS232 conversion

[vinu]

Hi,

I am working on GPS module which has a LVTTL logic level out on its comm 2 port and which needs a conversion to RS232 level. So I need to figure out what chip I need to use to do the conversion.

Thanks Vinu

[nmitech]

Simplest way is modified the second serial port, SCI1 of IsoPod_V2 for TTL signals. Let me take some pictures and show you the modification.

[nmitech]

Here it is,
http://www.newmicros.com/store/product_details/V2TTLMod.html

[vinu]

Hi moderator,

That is ofcourse a good idea. But it involves a bit risky work according to me. The lines on the bord of the Iso-pod are so near to each other that, i may get in to trouble. I am considering it as an option if no other is available for me. What is the probability of getting a IC from Maxim which can do the conversion form LVTTL to RS232. This would be helpfull in the long rum. So can i get some info regarding the IC i am suppose to use.


Thanks Vinu

[nmitech]

MAX232A will do the job.
http://pdfserv.maxim-ic.com/en/ds/MAX220-MAX249.pdf

You may want to use the DIP package,
part # MAX232ACPE for easy to assemble.

[vinu]

HI,

The DB9 connector has 4 active pins. They are

1) Clear to Send (CTS)--->Pin 7
2) Request to Send (RTS)--->Pin 8
3) Transmitter (Tx) ---->Pin 2
4) Receiver (Rx)----->Pin 3

The doubt I have is, which of them are outgoing pins and which of them are incomming Pins. We use the MAX232A, as the interfacing chip between the OEM4-G2L GPS module from Navman and the Iso-Pod X from new micros.

Thank You Vinu

[RMDumse]

So is this DB9 on the Navman? The meaning of which pin is an input and which is an output depends on wether the unit is wired to be a DataSet or a DataUnit. We wire our boards to be DataSets so they can talk directly to a PC. The Navman is "possible" wired the same way. You will have to investigate with them further.

The serial on the processors has only serial in and serial out. Generally, handshaking lines are wrapped back on themselves. So from what you've shown, Pin 7 should be wired back to Pin 8, or, put another way, CTS should be wired to RTS.

Our SI shown as RxD1 in the previous pictured link (after you do the level shifter) should "probably" come from Pin 2 and our SO shown as TxD1 in the previous pictured link (after you do the level shifter) should go to Pin 3.

The easy thing to do is to try it that way, and if it doesn't work, swap the 2,3 pins and try again.