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Serial Cable No Connection


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Hi all,

I feel like a complete idiot. I have just bought a Fon+ and a pl2303 serial to USB cable. I have then put together the three cables from the board to a rs232 female connector with a switch on the ground line.

No matter how many times I have tried I cannot get a connection to the device through any com port, using Putty. I have installed the drivers for the pl2303, and as I plug it into each USB port it is recognised as a different com port number.

I have only tried Windows 7 so far. Anyone have any experiences with windows 7 and this particular task?

Thanks,

jprknight

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Not that I know much about this particular topic, but I know there are two configurations of serial cable (in the same fashion as there are rj45 ethernet cables), one has the pins crossed over (null modem) the other does not, have you tried both (or the right one if you know which that is lol)?

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A way to test you've got the cable right is to short RX and TX and see if it echos back what you type in. That is the way I test my cables before risking the Fon to them.

Make sure that when you connect it you start without ground connected and plug it in once you get the start of output.

Or you can let the device boot then connect it.

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Hi guys,

Thanks for your suggestions. I only have the one serial cable which I bought on ebay. I have just put a mobo jumper on pins 2 and 3 and sure enough I get my input echoed back to me 100%.

So I now know I have the correct serial cable and I believe I have my cables wired into my serial port in the right configuration.

Here is my wiring setup http://yfrog.com/mrimg00017201008200925j does it look correct?

My black cable is ground, which I have in pin 5 on the serial cable, running through my switch and onto the left most connector on the Fon board.

White is Rx and goes from pin 2 on the serial cable to the second from the left on the Fon board.

Red is Tx and goes from pin 3 on the serial cable to the third from the left on the Fon board.

Having said all of this I am still struggling to get a connection. I have left off the ground for a couple of seconds. Let the Fon boot and then connect the serial. I have also left off the ground waiting for the start out the output, but nothing comes.

I think at this point I must have missed something pretty small, but big enough to stop the whole shotting match.

Anymore suggestions are more than welcome.

Thanks,

jprknight.

Edited by jprknight
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seeing as you've shorted rx and tx and got echo back you've obviously got the right pins on the serial cable but have you got them the right way round when going to the Fon? You've described them right in the text but I don't know the pin out of the 9 pin serial to check if they are going to the right pins.

Have you got the right baud rate? 9600, 8, 1?

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Ok I seem to be making progress.

1. plug in the serial connector.

2. power the fon.

3. Connect the usb end of my serial-usb cable into my laptop.

4. connect to com4 with putty.

I now see:

Léô{˵¿§¿¿sac¿5¿5=9/£åë

¿u59-#1¿;!!¿9-#¿¿59!#7¿¥¿5#5Cy¿!¿=;!ëCÿCÿCÿCÿCÿ»ÿ­ÿ«ÓÓ

!¿3-¿'!=7¿¥;¿¿'!=75ë«ÓÓ

!¿1!¿åës=-'=35¿'!=75£ëåëg!!)-#1¿3!;!=¿9!#3-1¿7==£££¿3!#7¿=¿!335¿=3åë[55¿;!#¿q_ma¿åë[5=7-#1¿3'=/¿3=¿!¿=;9=5£££¿

Cÿ is me pressing enter to try and make the thing work. I have read in other posts this kind of thing would hint a ground problem. So I got my multimeter again and tested the cable from the connection on my fon to the connection on the back of my db9 connector and it is good.

I have also tested with the waiting a couple of seconds and i still end up with garbage instead of real text.

Any thoughts?

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I have just connected one cable from the Tx on the Fon to the Rx on the serial cable, along with the ground and I get garbage as in my previous post.

If I power on without the ground or power on the ground shortly after powering up the fon I get nothing.

Edited by jprknight
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Hi Emeryth - Yes I have checked the voltage on my ground cable from the fon connector to the connector which is plugged into my serial cable. Looks ok.

The USB - Serial cable I have bought from ebay is here: http://tinyurl.com/2w5g267

Has anyone else been able to use one of these cables successfully? It is described as a USB to serial rs-232 db-9 adapter cable.

It echoes back input when I connect Rx and Tx; at this point I am in doubt wether the cable is giving me proper ground. The only thing which makes me think it does is the fact I only get garbage characters when I connect it. Without the ground I get no output when the fon boots from putty connected into the com port.

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I'd be tempted to dump the 'garbage' to a file, then open it so you can look at the binary (literally 1' and 0's) and see if your human eye can spot the pattern for ASCII characters. Maybe the bits in the bytes are been offset some how.

0DpTy.gif

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Hi Guys,

I have put the positive on transmit and the ground on ground an I get a negative intication. Reversing the multimeter connectors and I get 5v. So it looks like the pl2303 cable I bought is not good for Fon work.

I have found this on ebay: http://tinyurl.com/2epv52n is this the kind of cable anyone has used before, or should I go buy something else?

Thanks,

jprknight

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I'd be tempted to dump the 'garbage' to a file, then open it so you can look at the binary (literally 1' and 0's) and see if your human eye can spot the pattern for ASCII characters. Maybe the bits in the bytes are been offset some how.

Hey Sparda,

Thanks for suggesting this, unfortunately I would not know where to begin with this process. I think my cable is completely wrong.

jprknight

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