How to Build a Nokia Data Cable - The easy version
by M.Brent (Tursi)

This document details how to build a Nokia data cable presumably compatible
with the Nokia 51xx and 61xx series. This cable is F-Bus only, which is
enough to run the Nokia Data Suite and upload operator logos, which is all
I wanted to do.

Note1: The Nokia Data Suite software must be purchased from Nokia. And it
is *required* for the cable to work - the freeware programs don't work
without it installed.

Note2: I just took existing designs on the net, replaced the Max232 with
a Max233, and so there. The voltages it runs are probably not quite
right. The specifications and safeties are probably not as good. I am
not an electronics wizard. I just know this worked for me, and it's
far simpler than the stuff that everyone else is posting.

Note3: Since all I did was swap a Max232 for a Max233, you could take the
design of your choice and do the same thing. But, again, I don't promise

** If you fry your phone or PC, buy yourself a new one. Don't whine to me, **
** I don't know what I'm doing and I'm telling you so now. Your problem.   **

So, I wanted a cable that would let me upload Operator Logos to my 5190 phone.
But, I didn't want to spend $100 for a one-time upload. So, I hunted down
schematics, and freaked. What was with all the parts? Reading the designs,
I learned that the Max232 used most of those parts for it's power supply,
converting +5v to +10 and -5. Cool. While looking up which 232 to order, I
found the Max233. The Max233 has all the circuitry inside, and requires no
external circuitry to do it's work.

Downsides? It's a little bigger (20 pin vs 16 pin). That's it, really.

What's the point of the whole circuit? All it does is convert the phone's
TTL serial data into RS232 level serial data.

The circuit I'm about to describe is verbatim the typical operating circuit
from the Maxim documentation. I'm just nice enough to provide pinouts as
well. It's based on the 232-based FBus cable adapter at

What you need:
Maxim Max233 or equivalent.
1uF capacitor.
9-pin female DIN plug for serial port
Connector for your Nokia phone. (This is hardest. Buy a headset or one of 
the cheap PCMCIA data cable adaptors, that's what I used.)

Max233 pinout (DIP package):
 1-T2In					20-R2Out
 2-T1In					19-R2In
 3-R1Out				18-T2Out
 4-R1In					17-V-
 5-T1Out				16-C2-
 6-Gnd					15-C2+
 7-Vcc					14-V+
 8-C1+					13-C1-
 9-Gnd					12-V-
10-C2- (CS- in doc.. typo?)		11-C2+

9-pin DIN Serial Pinout (female plug)
	5 4 3 2 1
	 9 8 7 6

1-DCD		6-
2-RXD		7-
3-TXD		8-
4-DTR		9-

Nokia 51xx/61xx Phone pinout (looking at phone, keypad up)
	1 o 2   3 4 5 6 7 8 9

1-VIn		6-MBus
2-Pwm		7-FRx
3-Mic		8-FTx
4-Sgn		9-Gnd

The circuit: mostly just wiring point to point, so here are the points of interest:
-Connect Serial pin 1 (DCD) and Serial pin 2 (RXD) to Max pin 18 (T2Out)
-Connect Serial pin 3 (TXD) to Max pin 19 (R2In)
-Connect Serial pin 4 (DTR) to Max pin 7 (Vcc)
-Connect Serial pin 5 (Gnd) to ground (several points connect here)
-Connect Phone pin 6 (MBus) and Phone pin 7 (FRx) to Max pin 20 (R2Out)
-Connect Phone pin 8 (FTx) to Max pin 1 (T2In)
-Connect Phone pin 9 (Gnd) to ground
-Connect Max pin 7 (Vcc) to Capacitor C1
-Connect other lead of Capacitor C1 to ground
-Connect Max pin 12 (V-) to Max pin 17 (V-)
-Connect Max pin 11 (C2+) to Max pin 15 (C2+)
-Connect Max pin 10 (C2-) to Max pin 16 (C2-)
-Connect Max pin 6 (Gnd) and Max pin 9 (Gnd) to ground

That's all!!

Theory, as near as I understand it, is this. The circuit gets it's +5v from the DTR line
on your serial port. The Max233 does all the work here. The capacitor is just a power
filter. Note that voltages running to the phone may be a bit high - there are a lot
of warnings online, but my phone took it without complaining. ;)

Basic testing:
-Make sure all your wiring is right. ;)
-Plug it into your serial port, and load up a terminal program.
-Set up the term program to talk to the serial port with NO flow control, and type a
 couple of characters to turn things on. If you test voltages now, pin 7 (Vcc) should
 have +5v or so, pin 14 (V+) should read around +10v, and pin 12 (V-) should read
 around -5v.
-Short out pins 7 (FRX) and 8 (FTX) on the phone connector (I just stuck a wire between
 them ;) ) and type. All characters should be echoed back to the term program. This
 verifies that data is being converted in both directions. Remove the short.
-Plug into the phone and load up the Nokia data suite. Play! :)

** Use this info at your own risk! **

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