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NUUKIAWORLD FBUS & MBUS

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FBUS & MBUS adapters

9. Frequently asked questions


9.1 Questions

CAUTION! NuukiaWorld does not give personal support about these building instructions. You must have the competence described in the chapter 2 to be able to fix the possible problems by yourself.

- 9.1.1 General

  1. Do these circuits really work?
  2. Many circuit designs for replacing the NDS cable published in the Internet require MAX 3232. I have had problems to find that IC. Do you mean that these circuits require only MAX232?
  3. Where can I buy the components?
  4. You have FBUS, MBUS, and dual-mode circuits. Which one I should build?
  5. Could you build one adapter for me? I would pay for it.
  6. I am not so good in English. Can you translate the instructions in my language?
  7. These pages are extremely fine. Can I copy and put the documents also on my home page?

- 9.1.2 Building

  1. I have built the adapter but when I measure the voltages from the board they are all near zero. What is wrong?
  2. Voltages on my dual cable are higher than on an FBUS cable. Is it ok?
  3. I have used much more common BS170 FET instead of the specified BF245. Why my dual-mode adapter does not work?
  4. What must be the power rating of the resistors? Also, should I use BF245A, B, or C?
  5. I have problems in FBUS communications with the dual-mode adapter. How to start searching for the reason?
  6. I have problems with my adapter that is slightly different than yours. How to fix it?
  7. There is a note that a "null-modem cable" must not be used. What kind of cable may be used with this device? Can I solder the cable directly on the circuit board?
  8. I cannot get the adapter work with my laptop. Why it works with my desktop PC?

- 9.1.3 Modifications

  1. I have already MAX3232 chips. Can you tell me the required modifications to use them?
  2. What modifications are required to use the adapters with a Nokia 2110/3110/8110/9000 phone?
  3. Can you tell me the connection of a cable for my phone that is not a Nokia GSM?
  4. Can I simplify the dual-mode circuit by using a manual switch between FBUS and MBUS modes? How to connect the switch?

- 9.1.4 Design details

  1. I have read the specifications of MAX232 and some compatible chips and all the documents say that the capacitors are essential parts in making the proper voltage levels. You have not used all of them. How it is possible?
  2. What is the purpose of the R1 between V+ and VCC? What are the consequences of connecting pins 2 and 16 of the MAX232 together? I have tried that and apparently, did not find much difference. How is the value of R1 derived?
  3. How you prevent voltages higher than 3 volt entering the phone? There are no zener diodes.
  4. Has the diode D4 incorrect polarity? It prevents the data flow from MAX232 to the FBUS Rx pin.
  5. Do you have any official documentation about the FBUS or MBUS?

- 9.1.5 Software

  1. Where can I find software for the cable, for example the Nokia Data SuiteTM? Can you give some URLs?
  2. Should the NDS installation software detect the presence of the phone in a COM port?
  3. What is the software protocol of the FBUS and MBUS? I need to implement my own application.
  4. Why cannot I use stardized AT commands with these cables?
  5. I tried the dual-mode adapter with LogoManager and it failed with message "Accessory not supported". Other applications work fine. What is wrong?


9.2 Answers

- 9.2.1 General

  1. Do these circuits really work?

    Yes. As far as the I have been used it and its previous versions with my Nokia 6110 (since November 1998). The circuits are first taken into my personal use (because they are designed just only for it). After that, if I have time, I will publish the versions here in the Internet.

     

  2. Many circuit designs for replacing the NDS cable published in the Internet require MAX 3232. I have had problems to find that IC. Do you mean that these circuits require only MAX232?

    That is the idea. I had problems to find a single MAX 3232. MAX 232 is much more common and, as I have seen much inexpensive than MAX 3232. Changing the chip type was not a straight-forwarded operation, but now you can find the finished circuit designs ready-to-build on these pages.

     

  3. Where can I buy the components?

    The components are quite common and can be bought at your local component retailer. You have to find out the dealers by yourself. Note the components marked "Equivalent*" in the component lists; you can use them without any problems. I cannot say the price at your dealer, but it should not be higher than 7 without the phone connector.

     

  4. You have FBUS, MBUS and dual-mode circuits. Which one I should build?

    Nokia Data SuiteTM 2.0 and most of the freeware third-party programs use the FBUS communications method. So it is usually enough to build an FBUS-only adapter. The MBUS is required with some Nokia's proprietary service applications.

     

  5. Could you build one adapter for me? I would pay for it.

    I have no possibilities or interests to start producing these adapters. You can imagine how many have asked for this. Ready-to-use adapters may be easily purchased by persons who had not bought the Nokia Data SuiteTM and may key up into using pirate copies of NDS.

     

  6. I am not so good in English. Can you translate the instructions in my language?

    The instructions are published only to help other interested persons when facing similar problems as I had. Although I try to update and make this English version better, I have no time to translate the whole manual to another language.

     

  7. These pages are extremely fine. Can I copy and put the documents also on my home page?

    No. Due to the continuous updating and expanding I do not give permission to copy these pages. This will ensure that every reader will get the same most up-to-date information from these instructions. Instead of copying these pages, you are encouraged to put a hyperlink pointing to the main page anywhere you want.

- 9.2.2 Building

  1. I have built the adapter but when I measure the voltages from the board they are all near zero. What is wrong?

    The voltages will appear on board only if some program is using the corresponding COM port. For basic measurements and tests you can use a general-purpose terminal program like HyperTerminal. See the chapter 3 for details.

     

  2. Voltages on my dual cable are higher than on an FBUS cable. Is it ok?

    The voltages may be higher with a terminal program in a dual-mode adapter than in a single-mode adapter. Most terminal programs assert both DTR and RTS simultaneously, and in Nokia software assert only DTR with FBUS and only RTS with MBUS. It is not a problem.

     

  3. I have used much more common BS170 FET instead of the specified BF245. Why my dual-mode adapter does not work?

    You have totally wrong component in your circuit. The BS170 is an N-channel MOSFET, and the dual-mode circuit cannot operate with a MOSFET (because the substrate is usually connected to the source pin in MOSFETs making them asymmetric). The circuit requires a symmetric N-channel FET [Philips1996][Siliconix1997] and in general only such JFETs are available as discrete components. Do not try to substitute the JFET with much more common MOSFETs.

     

  4. What must be the power rating of the resistors? Also, should I use BF245A, B, or C?

    There are only negligible losses in the resistors (you cannot draw too much power from the serial port). So the smallest possible resistor power rating is ok for all resistors (for example 0.25 W). There is no difference between BF245A, B, or C in this circuit.

     

  5. I have problems in FBUS communications with the dual-mode adapter. How to start searching for the reason?

    To start solving your problem, try to disconnect the D or S of the FET Q1 to make the adapter FBUS-only and try again. Also you can try holding the FET connected and adjusting the R3 to be larger than the specified 10k. If this helps, there may be something wrong in the RTS circuit or the FET type is incorrect.

    The problem may be in your computer and the application together - if your computer supplies lower RS 232 levels and if the application powers the adapter more sparingly, it is possible that the adapter will not be powered properly. Test using a 4.5 V - 9 V battery between V+ (pin 2) and GND (pin 15) of the MAX232. If this helps, there may be something wrong in the power supply part of the adapter or in the serial port of your computer.

     

  6. I have problems with my adapter that is only slightly different than yours. How to fix it?

    I cannot help anybody even with my own circuit design, so I absolutely do not help anybody with third-party circuits.

     

  7. There is a note that a "null-modem cable" must not be used. What kind of cable may be used with this device? Can I solder the cable directly on the circuit board?

    The wires in a null-modem cable are connected to make possible to connect two computers together via their serial ports. There are female connectors on both ends of the cable.

    This device requires similar cable as an external modem. The pins are connected directly to the opposite end and the connectors of the cable are of opposite sex. If you solder the cable directly on the circuit board, just map the pin places on the board directly to the connector. The connector on the cable is the same as would have been soldered on the board.

     

  8. I cannot get the adapter work with my laptop. Why it works with my desktop PC?

    Probably the problem is low serial port signal levels with your laptop - they are too low for this kind of adapter. If you are trying the dual-mode adapter, change the wiring to single-mode and try again.

    The super miniature dual-mode adapter uses a low power (MAX3xxx series) IC and should work with all PCs. Adapters using MAX232 may fail with some PCs.

- 9.2.3 Modifications

  1. I have already MAX3232 chips. Can you tell me the required modifications to use them?

    The MAX232-based circuits do not work with a MAX3232 without large modifications.

    You can use the MAX3232 chip in a circuit based on the super miniature dual-mode adapter design. You have to change the circuit board layout, because the pin outs in MAX3232 are different than in MAX3221. Please note that the unused transmitter input of the MAX3232(T1IN or T2IN) must be tied to VCC.

     

  2. What modifications are required to use the adapters with a Nokia 2110/3110/8110/9000 (or some other) phone?

    If the phone support the corresponding bus (FBUS and/or MBUS), then the circuits may be uses as such. You must only find out the correct pin arrangement of the phone connector to connect an adapter to your phone. I cannot help you with this problem.

     

  3. Can you tell me the connection of a cable for my phone that is not a Nokia GSM?

    No, I cannot. The data cables are brand-specific and I am specialized only in Nokia GSM adapters.

     

  4. Can I simplify the dual-mode circuit by using a manual switch between FBUS and MBUS modes? How to connect the switch?

    Yes you can. I personally prefer the soft-switch solution, because it is not actually very complicated. To use a manual switch, just remove FET Q1 and resistor R2 and solder the switch to the S and D pins of the former Q1.

- 9.2.4 Design details

  1. I have read the specifications of MAX232 and some compatible chips and all the documents say that the capacitors are essential parts in making the proper voltage levels. You have not used all of them. How it is possible?

    I have read the specification more carefully. According to the MAX232 data sheet 19-4323; Rev 7b; 11/97 [Maxim1997], you can leave capacitors away:

    (From page 14) "For applications where a +10V external supply is applied to the V+ pin (instead of using the internal charge pump to generate +10V), the C1 capacitor must not be installed and the SHDN pin must be tied to VCC."

    My new designs use rectified DTR or RTS signal to form this "+10V" (voltages down to 5.5 V is allowed, down to 3 V works fine) connected to V+. The other charge pump on the chip is then disabled by removing the capacitor (called C1 by Maxim) from pins 1 and 3.

    The VCC current is therefore decreased and a proper VCC level (more than 4.5 V) is easier to obtain, because there are no power losses of the other charge pump and the absolute voltages of V+ and V- are smaller, so the power driven to the load resistor of the computer serial port RxD is smaller.

    This is one of the reasons for that you cannot use a MAX3232 chip (or equivalent) with these designs (see the super miniature dual-mode adapter design if you are using MAX3xxx series chips).

     

  2. What is the purpose of the R1 between V+ and VCC? What are the consequences of connecting pins 2 and 16 of the MAX232 together? I have tried that and apparently, did not find much difference. How is the value of R1 derived?

    Usually there will be no problems if the pins 2 and 16 of the MAX232 are tied together. The internal resistance of the PC serial port drivers may also act as resistor in this simple zener regulator circuit.

    But, if you tie the pins together, the pin 2 is never allowed to go higher than 4.7 volts. According to the specifications, the pin 2 voltage (V+) should be higher than 5.5 V. The resistor gives a possibility for pin 2 to be higher than the pin 16, which is hard-wired to 4.7 V (or less).

    I have thought removing the resistor to reduce the number of components by one, but I decided to keep it in the circuit. Its value is just something. A small value drops the V+ voltage, and a high value drops the VCC voltage.

     

  3. How you prevent voltages higher than 3 volt entering the phone? There are no zener diodes.

    The FBUS TX is connected directly to T2IN of the MAX232. The T2IN has impedance of 400 kohm and the overvoltage (which can be seen when no phone is connected) disappear safely because of the load of the phone output/CMOS input diodes.

    FBUS RX/MBUS line has a schottky diode. Its direction is important. When the R2OUT is put to 4.7 V (with a low impedance) by the MAX232, then the diode is reversed and only very low current will go through it. So there are no problems in this case either. There is overvoltage also in FBUS RX/MBUS pin without a phone, because of the (very small) leakage of the diode.

     

  4. Has the diode D4 incorrect polarity? It prevents the data flow from MAX232 to the FBUS Rx pin.

    By removing or reversing the safety diode D4 you will put you phone under voltage stress. Remember that the direction of a diode does not tell the direction of information flow but the direction of the electric current. By using D4 the R2OUT is made "sinking-only" (current flows only into it and pulls the FBUX Rx to the "low" level.

     

  5. Do you have any official documentation about the FBUS or MBUS?

    All my FBUS and MBUS information is gathered with my own measurements. I have no official information about the buses or any information about the protocol.

- 9.2.5 Software

  1. Where can I find software for the cable, for example the Nokia Data SuiteTM? Can you give me some URLs?

    There are many freeware programs available in the Internet. Please search the web by yourself. The Nokia Data SuiteTM is licensed and commercial software, so it must be bought at your local Nokia dealer. It cannot be downloaded from the Internet.

     

  2. Should the NDS installation software detect the presence of the phone in a COM port?

    I have not tested the phone detection of the NDS installation software personally. If you do not know if your homemade adapter works with the NDS software, I recommend you to choose the correct COM port manually or use the original cable supplied in your Nokia Data SuiteTM package in the installation phase.

     

  3. What is the software protocol of the FBUS and MBUS? I need to implement my own application.

    The interface behavior on software level is not my business. I have researched only hardware problems in this case and I have no documentation on the protocol.

     

  4. Why cannot I use stardized AT commands with these cables?

    The important point is that only new phones supports direct flow-controlled connection between PC and phone. Because my adapters are intended for phones without handshaking, those phones you cannot operate them directly with the serial port. You need software that converts AT-commands to vendor-specific protocol. For example, Nokia Data Suite is a program for that.

    New Nokia phones do not need NDS, but therefore they need more complicated cables (for example, DLR-3 cables include a microcontroller).

     

  5. I tried the dual-mode adapter with LogoManager and it failed with message "Accessory not supported". Other applications work fine. What is wrong?

    It is a feature of LogoManager (when compared to other applications). LogoManager initializes the serial port only partially and the handshaking settings will not be properly set with the LogoManager. The cable is switched in the MBUS mode instead of FBUS if you are using the LogoManager after an application that used hardware handshaking with the same COM port. To avoid this problem, start and close another FBUS application just before running LogoManager.

- © Copyright 1999, 2000, 2002 Panu M Tuominen. All rights reserved. Republishing this document partially or completely is forbidden. Internet hyperlinks to the main page are allowed and such linking is encouraged. You are doing everything at your own risk. See the WARNING! in the general information page.

For example, Nokia 5110 and Nokia 6110 are 5100/6100 series phones. The tests have been done with Nokia Data Suite 2.0, Nokia Logo Express, LogoManager demo version, and a Nokia 6110.

31.1.2002 - nuukiaworld@gmail.com
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