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Connecting to a Satellite tranceiver with PC

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Silver TT

New Member
Hi I could use some help with a project that I'm stuck on. Any help would be GREATLY appreciated!

I am trying to connect to a GPRS modem using my computer, so that I can test the serial functions that I'm trying to enable. I am using PuTTY (the terminal emulator), and trying to connect to the device using an RS232 port with a TTL adapter. The GPRS unit uses 3V vlogic, so the RS232 must be stepped down. Here's a link to the GPRS unit:
https://ca.globalstar.com/shop/index.php?main_page=product_info&products_id=79

The manufacturer of the GPRS modem has supplied a program to flash new software onto the unit - and it has a built-in function that can automatically search all of the ports on the computer and return the ESN (electronic serial number) of the device. When I use the manufacturer program, the TTL adapter functions properly and the program finds the device and can communicate. However, I cannot connect to the device using a terminal emulator? The emulator should allow me to type if the connection was made successfully. The rep for the GPRS claims that "PuTTY cannot send binary to the modem". This has got me very confused. If I understand correctly, the translation character set in PuTTY does just that - it converts text to binary! Perhaps I have selected the wrong character translation set? Can someone point me in the right direction here? Any help.

This is part of a larger project to connect an Allen Bradley Micro800 (http://ab.rockwellautomation.com/Programmable-Controllers/Micro820) PLC to the modem using an Ethernet to TTL adapter. The adapter I want to use is this: http://www.wiznet.co.kr/product-item/wiz105sr/

Thanks for the help,
Sean
 

Diver300

Well-Known Member
Most Helpful Member
That isn't a GPRS modem. It's a satellite transceiver.

Generally, if you are using a terminal emulator, it should send each character as serial ASCII as you type it.

You could do a loop back test. Connect RX to TX on the serial port and see if what you type in the terminal emulator comes up on screen. If yours screen has what you type anyhow you should get each character twice.

Examples:-
If you type "abc" with nothing connected, and see nothing on screen, when you connect RX to TX you should see "abc"
If you type "abc" with nothing connected, and see "abc" on screen, when you connect RX to TX you should see "aabbcc"

That indicates whether your serial emulator is working.

At a voltage level, you should see around 3 V on the TX line, which should dip slightly as you send characters. If you slow the baud rate down as far as it will go, your voltage dip becomes more obvious. If you have an oscilloscope, you should be able to see the individual bits of the ASCII character.

Does the transceiver have a command set like a modem has? Are there simple command that you can use to check communications?
 

Silver TT

New Member
Thank you for your reply. I've done the loopback test and it's working fine. The manufacturers software for the satellite tranceiver works with my cable.
There is 1 simple command with which you can query the tranceiver to get the serial number. Problem is PuTTY won't let me type!
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Thank you for your reply. I've done the loopback test and it's working fine. The manufacturers software for the satellite tranceiver works with my cable.
There is 1 simple command with which you can query the tranceiver to get the serial number. Problem is PuTTY won't let me type!
As the loopback test is working fine, then so is PuTTY.

Presumably you are aware that the default setting for PuTTY (and other serial terminal emulators) is NOT to echo the characters as you type them, it relies on the target echoing them back for you to see them. Does your target do that?, or is is set not to? - it's common for modems etc. to default to echoing though.

But as others have said, your device ISN'T a 'modem', so how do you know what it's supposed to reply, if anything?.
 

Silver TT

New Member
Thanks, I turned the local echo on w/ line at a time. Still having some issues though.

I only know of a couple commands that the transceiver should respond to, in hexadecimal they are:
AA 05 01 50 D5
and
AA 05 05 74 93

I used a serial port monitor to confirm that these commands are indeed what the manufacturer's software queries the device with to get the serial number and firmware.
This also confirmed what my issue is. PuTTY is translating my ascii text to hexadecimal, but I'm typing the hexadecimal values already. Is there a way to stop this from happening?
What does this mean for my PLC that I eventually want to use to send data to the device? Will I have to ensure that the PLC is capable of sending data as hex?

Thanks,
Sean
 
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