Null modem vs crossover cable

[Anthony5]

I need to flash firmware to a bricked satellite receiver.

The procedure is to use a null modem cable.In the software used to flash the firmware you will have to select the COM port.

I've been to Tuckom today and most of them have no idea what a null modem cable is, and those that have a RS232 cable have no idea if it is a straight serial cable or a crossed over null modem.

I can have however a crossover Ethernet cable, so my question is if i can use this as a replacement for the null modem cable.

Will the Ethernet port be recognized as a COM port?

Edited March 8, 2015 by Anthony5

[Anthony5]

As an alternative, anyone know where I can order a null modem cable online within Thailand?

I know I can get it on Ebay, but that will take at least 2 weeks or more to arrive.

[alocacoc]

What brand/model is the satellite receiver? If it's a Dreambox, you should be able to boot up into the update mode while pressing channel down and/or channel up while you plug the power connection. Then on the osd of the receiver you see the IP address which you may connect by a rj45 connection.

I know, it can be a challenge to find such items in thailand. Otherwise you could solder a standard rs232 cable by your own. It's not that difficult.

Edited March 8, 2015 by alocacoc

[Anthony5]

It's a skybox and it's in bootloop, and but doesn't show boot screen, so it need the handshake.

I bought one of those RS232 cables at Tukcom but it is a normal serial cable.

[alocacoc]

Then you can do it by yourself.

Or you go - for instance - to the electronic shop downstairs at tukcom. They are able to solder it.

[lopburi3]

They should be able to make you a cable - I have done myself by cutting in middle but shops often make to required size so if you show them below should not be a problem to make.

[Anthony5]

Then you can do it by yourself.

Or you go - for instance - to the electronic shop downstairs at tukcom. They are able to solder it.

Now it gets interesting. Below is the image from the null modem cable as it was posted, and I found a similar image on a random website. Take not that pin 1 - 5 are uplined in the different direction .

Which one is the correct one?

[Jdietz]

Pin order mirrors between male and female connectors (obviously).

Only really important pins are 2, 3, and 5 (TX / RX / GND) to 3, 2, and 5 (RX, TX, GND).

Can indeed cut open a standard cable in the middle and swap 2 and 3.

If you need hardware handshaking for some reason can use the more elaborate wiring which honors RTS/CTS/DTR

[Anthony5]

Pin order mirrors between male and female connectors (obviously).

Only really important pins are 2, 3, and 5 (TX / RX / GND) to 3, 2, and 5 (RX, TX, GND).

Can indeed cut open a standard cable in the middle and swap 2 and 3.

If you need hardware handshaking for some reason can use the more elaborate wiring which honors RTS/CTS/DTR

My cable is female to female, but in some images like the one posted by Alocacoc the numbering goes 5 -> 1, while in other images the wiring goes 1 -> 5, this makes a difference as to which are pin 2 and 3.

I don't understand the last line of your post though.

[lopburi3]

Believe we are getting confused because looking at front and back of connectors so number appear reversed but are actually not - and last line of handshaking was in reference to the other wires which for basic use are not required for passing data only.

[Anthony5]

Believe we are getting confused because looking at front and back of connectors so number appear reversed but are actually not - and last line of handshaking was in reference to the other wires which for basic use are not required for passing data only.

I will write 50 times Anthony is an idiot.

The corresponding numbers are written on the socket , but at my age I'll need a telescope and a 1500W halogen to see them.

[Anthony5]

Found full handshake null modem cable at Element14 for 127 Baht.

[Anthony5]

Just a heads up in case someone else wants to order such a 127 Baht null modem cable from Element14.

It took 40 hours to process the order, then I was informed that on every order below 3000 Baht they slap a minimum order fee of 750 Baht, so think again if you want to order something from Element14.

I have thanked them and ordered the cable on Ebay now for 175 Baht.

[Anthony5]

Some more help please. As you will be aware I didn't order the cable from Element14 because I refuse to pay a 750 Baht "fee" for a 127 Bht cable.

On Ebay there ar plenty for 200 Baht shipping included, but there are 2 different wiring diagrams available. One has 4 > 6,8,1 and the other has 4 > 6 and 7 > 8.

Which one would be the better choice.

OR

Pin 2 ---------- Pin 3

Pin 3 ---------- Pin 2
Pin 4 ---------- Pin 6
Pin 5 ---------- Pin 5
Pin 6 ---------- Pin 4
Pin 7 ---------- Pin 8
Pin 8 ---------- Pin 7

Edited March 15, 2015 by Anthony5

[alocacoc]

I would prefer this:

It says in German, Suitable for programming for all DVB-receivers (Sat, Cable, IPTV).

It looks like, it's the wiring as on your second cable,

Pin 2 ---------- Pin 3

Pin 3 ---------- Pin 2
Pin 4 ---------- Pin 6
Pin 5 ---------- Pin 5
Pin 6 ---------- Pin 4
Pin 7 ---------- Pin 8
Pin 8 ---------- Pin 7

[alocacoc]

If you stay in Pattaya, i could name you a shop which have most likely such a cable (or a adapter) in stock.

Edited March 16, 2015 by alocacoc

[Anthony5]

If you stay in Pattaya, i could name you a shop which have most likely such a cable (or a adapter) in stock.

Yes I stay in Pattaya, shop name would be much appreciated.

[alocacoc]

The shop is about 100 meters after the PTT gasoline station if you come from the Sukhumvit. It's on the right side. A small shop with ten thousands electronic spare parts.

See here:

google.de/maps/@12.908666,100.887792,3a,18.7y,4.17h,86.12t/data=!3m4!1e1!3m2!1sR0QGQFHSSbZv4JTDleRQ7g!2e0

Good luck.

[Anthony5]

Update:

Today I received the null modem cable I ordered from Ebay on 20 March. It took a bit longer because of songkran, but I got it.

Plugged in the cable in the PC and Skybox and upgraded successfully the box that was in boot loop before.

Total price for the cable was 3.35$ or 108 Thai Baht. Little bit less than the 877 Baht Element14 wanted to charge me.

In case someone else needs a cable in the future here is the link.

http://www.ebay.com/itm/191539319831?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT