The following Information is gathered just by listening into the MBUS-Communication and by guessing and trying a lot. No PICs has been read out or disassembled. No Nokia DLR-3p has been disassembled or sniffed by me.

Note: Nokia MBUS ist sometimes also called M2BUS. Do not confuse this whith the I2C based Bus on some Motherboards.

Before you continue, you should get fimilar with the very basics of the MBUS-Protocol: The phone regulary sends the DLR3-Frame "1F,48,00,4E,00,02,01,xx,seq,checksum" to the µC in the dlr3-cable via MBUS, which devides into:
Field size Description DLR3 data
1 byte Protocol identifier - on MBUS always 0x1F 1F
1 byte Destination Addr 48
1 byte Source Addr (00=Phone) 00
1 byte Command 4E
2 bytes dl=data lenght 00 02
dl byte(s) Message Data, see below 01 xx
1 byte Sequence Number xx
1 byte XOR Checksum xx
The Cable should always anwser with a standard ack-message: "1F,00,48,7F,seq,checksum". Always use the sequence number generated by the phone, but your own checksum.

With the "first version" DLR-3 Cable, I made some connections and created some stress-situations to find out, how RTS,CTS, and the other Signals are coded into the last message byte.
Bit Pos Description
7 MSB always 0
6 always 0
5 always 0
4 always 0
3 ??? looks like DSR, because it is 1 all the time
2 0: Datamode, 1: Idle or Voicecall
1 DCD; 1 if you have no connection, 0: CONNECT & CARRIER
0 LSB CTS; 0 means, the PC is allowed to send data;
1 means, he PC have to wait (for example while establishing a connection or when sending too much data at once)

RTS Signaling

RTS is delivered to the phone via the XEAR pin. Pulling it low (through 1K) means, the phone is allowed to send. Having it high, or letting it float will prevent the phone from sending any data to the PC.

DTR: Connection Hangup and FBUS-Switch

For the DTR-Signal the XMIC-Pin is used. While it is usually used to identify a DLR-3p cable to the phone, it can be used as DTR after the MBUS-communication with the phone has been established. Thanks to Anatoly Sudanov for the DTR-Info above!

Dropping DTR causes two things: a) an active dataconnection is terminated, and b) the Serial-Pins are switched from AT-Mode to FBUS-Mode.

IP WAP-шлюза:
Порт: 9201

Powered by COMPPAG 0.50
2022-2024 © Compys S&N Systems