SCHEMATICS FOR DAU-9P (MBUS)

There is two versions, version to work with I.C. MAX3232, that it's not easy to find and version with MAX232. Both versions works for Nokia Data Suite (DAU-9P) and Wintesla (M2Bus).

All interface is powered by RTS and DTR signals. D1 and D2 is recommended in Shottky design since lower dropout. The voltage regulation (which should be 3.3V) is here done by 5V regulator with diodes D3 - D5 on which is drop about 1.8V, so final voltage is 3.2V, on diode is drop about 0.6V, so before regulator it may be 4.4V, after regulator about 4.1V, drop on D3 - D5 diodes is about 1.8V and in this case voltage can be 2.3V) - it can be wrong (I tested MAX3232 works fine on voltage 2.0V), but amperage of COM port will be unnecessarily bigger. Zener diodes DZ1 and DZ2 are VERY important to safety of Your phone. Normally are values of log. 1 about 3.3V and little overcross of this value can damage the phone – so power blast at turning on computer or connecting interface into computer. DZ1 and DZ2 diodes cuts-down this voltage to 2.7V - it is enough to log. 1 and it is hardly under maximal voltage value. In all, it is standard wiring of MAX232. Pins No.8 (R2IN) and No.9 (T2IN) You needn't to connect to ground.

If you use a MAX232 is necesary use a 1k ressistor to reduce voltage at PIN 10 from I.C. so we guaratee a correct voltage at Tx for the phone and it's not necesary 4007 diodes because Max232 work at 5V.

To use MBus interface we need only add a 4148 diode between RX and TX and get a new cable from TX to connect it to PIN 6 in phone connector.

To get phone connector use a handsfree portatil (not nokia original, because it's too expensive) and cut connector. Be sure that it's not thermo-sealed and it uses all pins.

I recommend you to use Max3232 version, because using Max232 comunication with phone using FBUS (Data Suite) sometimes may be failed.
 

Component list:

Max3232 Version (original) 3x 4148 Diodes 3x 4007 Diodes 1x Voltage regulator 78L05 2x Ceramic Capacitors 100nF 4x Electrolitic Capacitors 1 microF 2x Zenner Diodes 2V7 1x I.C. MAX3232 1x Female 9 pin serial PC conector 1x Conector phone

Max232 Version (cheaper) 3x 4148 Diodes 1x Resistor 1k 1x Voltage regulator 78L05 2x Ceramic Capacitors 100nF 4x Electrolitic Capacitors 1 microF 2x Zenner Diodes 2V7 1x I.C. MAX232 1x Female 9 pin serial PC conector 1x Conector phone

Phone Connector pinout

!!!WARNING!!!: DAU-9P is powered by RS-232 port, and requires at least 7,7 V for the circut to work. This is not true for most Notebooks and USB-COM controllers, since their signals are 5,5 - 6,5 V in most cases, so DAU-9P may not work! In this situation you can use DAU-9P Notebook Edition by Adrian Dabrowski (atrox).