Siemens cell phone communication cable. Scheme, description

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Cable for connection of cell phone Siemens S25/C/M/S35 with computer. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering /Mobile telephony

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What is it for?

The idea to solder a cable to connect the phone to the computer came to me only with the third mobile device. That is, theoretically, I could "fasten" my first S10 Active to the PC. However, better late than never.

After another upgrade (this time from C25 to S25) I found out that there is a lot of software with which you can combine the capabilities of two devices - a PC and a mobile phone. Of course, most of them work fine through the infrared port, but I don't have a laptop, and by that time I hadn't done the "IR eye" yet. But most of all in the cable connection I was attracted by the opportunity to independently change the firmware in the device.

Of course, the cable could just be bought. I do not mean the original accessory from Siemens (for which they ask for an inadequate amount of money - about $ 100), but quite affordable ($ 20) and workable cord made in Taiwan. But for me personally (as for a radio amateur in the past) this is completely unsportsmanlike.

The search began as usual - on the Internet. I found a lot of schemes, and almost all turned out to be different! Which of them should be taken as correct? This was to be decided by myself. I am not talking about the fact that I had to translate from German ..

Theory

As a basis, I took the description from the German site, nobbi.com - there were at least some comments, in particular about the microcircuits used. Having printed out other variants of the schemes found on the Internet, I began to work out the "golden mean".

Here's what happened in the end. I will try to explain my actions in general and the choice of components in particular.

Cable for connection of cell phone Siemens S25/C/M/S35 with computer

The main part is the MAXIM 3232 chip. This is a commonly used TTL-CMOS signal level converter with a supply voltage range of 3..5,5V. For the S25, the Germans suggested using it. In other descriptions, there are circuits on the MAX 232, which is identical to the 3232, but is designed for a 5V supply voltage. Accordingly, the signal amplitudes will be 5V, which is incorrect in relation to S25, which has a supply voltage of 3,6 V. Although it can be used as a last resort, I don’t see much point in this ..

Also, in many circuits, the values \u0,1b\u10bof the capacitors of a typical inclusion of an IC vary greatly - from 0,1 to XNUMX microfarads. I still did not understand what caused this, because in the proprietary specification it is clearly indicated that all capacitances are XNUMX microfarads. I can only assume that it is possible to use other denominations, the main thing is that they be the same.

Another controversial point: in half of the circuits found, the voltage supplied to the IC was reduced by two conventional diodes and one Schottky diode connected in the forward direction. Thus, if the input of the stabilizer is 5V, then 3V comes to the IC. However, in real conditions (without using an external power supply), after the stabilizer it is rarely more than 4V, mostly 3-4V. So there is simply nothing to take away here :-)) Therefore, I did not install diodes, but to protect the phone input I hung a 2,7 V zener diode at pin No. 6.

The power supply of the converter (circuit) is implemented from the pulses of the COM port, which, after the diodes in direct connection, are fed to the input of the voltage stabilizer. You can take any five-volt stabilizer; I used KR1055EN **** - a domestic analogue of 78L05 (specification) in a very convenient TO-92 package (like a KT3102, 503 transistor, etc.). The current consumed by the IC is 9-10 mA, so there is no point in putting a "big" ROLL 5A (7805).

Here I want to add that it is possible to completely abandon the power stabilization unit. You can power the IC directly from the phone's battery - it is guaranteed to deliver almost 4 volts (dashed line in the diagram). This is implemented by Sergey Oskin in the cable for communication between S25 and PalmM, icenet.narod.ru/SC/sc000200.php. The only disadvantage of such a connection is that the phone's battery is still discharged, albeit with a small current (about 8 mA).

Practice

In the end I needed:

IP MAXIM 3232 - 120 rubles,

Tantalum capacitors - 0,1 uF x 25V - 4 pcs. for 8 rubles,

Electrolytes 10 and 100 microfarad x 25V - 2 rubles each,

Ceramic capacitor 0,1 uF - 2 rubles,

Domestic analogue 78L05 - 1 rub 50 kopecks :-)

Two diodes type KD522,

Zener diode for 2,7 V - 4 rubles,

Phone connector - 50 rubles,

Connector for COM port 9 pin - 15 rubles,

I already had a textolite and a microdrill ..

There are few details, especially if you do not put 78L05. Therefore, a printed circuit board (PCB) can not be made at all, but a surface mounting can be dispensed with. I quickly applied the drawing with decals and etched the board. It just so happened, but I was not able to scan the PCB wiring without details .. A breadboard is also quite suitable - "perforated", with metallized holes without tracks.

Cable for connection of cell phone Siemens S25/C/M/S35 with computer

Textolite 1mm, imported - almost transparent. Yellow "droplets" - tantalum capacitors. The zener diode is soldered directly to the IC (on the board on the right).

Cable for connection of cell phone Siemens S25/C/M/S35 with computer

It makes no sense to make separate contacts for cable desoldering - I soldered the wires directly to the contact pads of the elements without any problems.

Almost all the parts I bought in the store. I was very lucky with the phone connector - I managed to buy it separately for 50 rubles on the Mitinsky market. For the sake of the connector, you can buy the cheapest Chinese charger or "Hands Free", but this is already 150-200 rubles. As a housing for the board, I used a 9-pin plug housing with a socket for a UTP plug (30 rubles on the market) with a cut of a regular 9-pin COM connector glued on top. It turned out quite acceptable .. The wire can be taken from any faulty mouse, although IMHO a shielded wire is still preferable.

Cable for connection of cell phone Siemens S25/C/M/S35 with computer

It is not at all necessary to look for a connector with all the contacts, 3-4 is enough. pin numbers are marked next to the pins.

Cable for connection of cell phone Siemens S25/C/M/S35 with computer

I glued the halves of the cases with dichloroethane - they hold up perfectly. The cord made about one and a half meters in length.

I connected the assembled lace to a free COM port and launched S25Expl, members.aol.com/s25exp. The design worked immediately, no additional configuration was required. In case of problems, I would recommend re-checking the installation, running PortMonitor, sysinternals.com/portmon.php and parsing its messages when starting S25Expl. Or, as usual, resort to the help of an oscilloscope ..

By the way, not all programs work with a cable without external power. For example, NetMonitor is written in such a way that it does not send pulses necessary to power the IC at all :-) That is why there are misconceptions that NetMonitor supposedly works only through IrDA. I also had concerns that the service software for flashing devices requires external power. However, they were not confirmed.

The cable has been tested on several S25s and on a famous person's C35. Now it has an exclusive logo on the screen of the phone and a melody, thanks to which the people around always know who exactly the phone is ringing :-) I tried to connect the C25, but the S25Expl did not want to work with it, but the "service software" functioned normally. I have not changed the C25 firmware yet, but this is only for now ..

You can read about cell phone programming at icenet.narod.ru.

Author: ch0zen, ch093@mail.ru; Publication: ch.telemost.ru

See other articles Section Mobile telephony.

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