MBUS problem - Nokia 61xx and compatible

[Piotr C.]

Hello,

I'm currently working on some project - interfacing nokia to '51
microcontrollers (my telecomm. studies require this). At a time I'm testing
this with PC thru RS232.

The FBUS connection is alright (but speed - 115200 - is to fast for a
standard '51, so I chose MBUS 9600). With MBUS I have some problems.

My phones (5110 and 6110) seem to 'go asleep' - don't reply to frames sent.
But if I press 'cancel' just before and during transmission, it wakes up and
everything is OK. While performing some longer transmission, eg. downloading
all sms, program hangs after about 2 sms and goes on again after pressing
'c' on the phone.

I use mygnokii/win32.

The made a couple of cable versions:
1) Rx from PC (thru max232) directly to mbus, Tx thru 1N4148 diode
(MBUS --|>|-- max232.Tx)
2) BC 177A transistor instead of diode: E-mbus, B-max232.Tx, C-gnd)
3) No additional parts, Rx/Tx short to MBUS
4) Universal nokia mbus/fbus cable

In all the cases it works the same way.

MAX232A i tested with are both original Maxim and some generics; connected
alright, externally powered - works (cause fbus works).

So what is wrong?

And a diffrent question, not related to gsm: did anyone tested Atmel 89c2051
@22.118MHz with interrupt-runned serial transmission at 115200?

Best regards,

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