FBUS is the common name I will use for the phone-host (or phone-accesory) communication protocol utilized by Nokia phones. It is used over several protocols throughout phone models; MBUS (single duplex asynchronous serial), FBUS (full duplex asynchronous serial), IRDA (full duplex asynchronous serial infrared), and even BlueTooth.
A good example of a fully working open source *BUS implementation can be found in gammu (GNU All Mobile Management Utilities) .
This excludes checksums and sequence numbers (for packet splicing) that are protocol specific.
ACK packets are different (only 6 bytes long). Normal headers contain the following bytes:
| Offset | Size | Meaning |
|---|---|---|
| 0x00 | 1 | Frame type |
| 0x01 | 1 | Destination address |
| 0x02 | 1 | Source address |
| 0x03 | 1 | Packet type |
| 0x04 | 2 | Packet size |
| 0x06 | 1 | Destination subsystem |
| 0x07 | 1 | Source subsystem |
Frame type signifies on which media the packet is sent.
| ID | Meaning |
|---|---|
| 0x1C | FBUS (Cable) |
| 0x1E | FBUS (IRDA) |
| 0x1F | MBUS |
The address identifies a device connected to the *BUS.
These are usually used:
| ID | Device |
|---|---|
| 0x00 | Phone |
| 0x0C | PC |
The exact address used by the PC doesn't matter, as long as it is valid (<0x80).
Especially those last two bytes (source and destination subsystem) are not widely known. Most *BUS descriptions and utilities incorrectly count them in with the packet payload, instead of the header they belong to.
This usually does not give a problem, as the Nokia OS contains a layer to route packets with Destination Subsystem=0 to the approciate subsystem.
Source subsystem should never be 0, or else the packet is ignored. 0x01 is the safest value AFAIK.
| ID | Meaning |
|---|---|
| 0x00 | Automatic |
| 0x01 | LOCAL |
| 0x02 | DEV_IO (sent to task but not processed on 331x) |
| 0x06 | SIML2 (sent to task but not processed on 331x) |
| 0x08 | DDI (SMS and SIM memory functions) |
| 0x0C | GUI (sent to task but not processed on 331x) |
| 0xFD | Debug (ignored) |
Last updated: 2005-02-21 14:19
This site is the result of a great deal of assembly code reading, research, countless (mostly futile) searches for data sheets, cross-referencing and analysing. If you use this information in any way please mention wumpus <blacksphere@goliath.darktech.org> (and others in the credits section) in the credits of your program/document. And tell me :) If you have more information please contribute. If you just copy this, stick your name on it and call it yours I hope you get your genitals bitten off by a three headed monkey. Have a nice day.
No mobile phones were harmed in the production of this site.