AN #124 - SMS on Nokia 5110/6110 via microcontroller

Back in May of 2000 I thought it would be a simple matter to connect my newly acquired Hotchip Mini AVR board to one of my old Nokia 5110's (I had 2 workers and 1 in bits).

Note: Although I speak of 5110, the following AN will also work on 6110 as well.

After searching the net, I found many examples of code using AT commands, but not for the 5110, and they were in C, which I am not too familiar with.

So, out came the old 286 with the RS232 sniffer program (Serial Test), and next came many hours of packet capture, late nights and much caffeine.

FBUS/MBUS & 115200 Baud

First problem was whether to use MBUS or FBUS, MBUS would work at 9600 baud, but echoed everything.

FBUS worked at 115200 baud, easy to sniff, but not so easy to implement on the AVR. A crystal change to 11.059Mhz soon got 115200 working great.



The above diagram shows my connections to the 8535, I used an old personal handsfree connector that are commonly available. I did start out with a MAX232, and a DAU9 cable, which worked great but I thought I could bypass them. And it worked, and is still working, but I accept no responsibility if the above connection damages your cell phone.

The code is not finished, but on Power Up, it will show info from phone, display incoming callers number, and also receive (and delete) incoming SMS.

For those that asked for some more information on FBUS/M2BUS and Nokia phones, this NokiaCode file contains a useful code snippet (in C unfortunately) and also protocol descriptions and cable pinouts. They have been gathered from various sources, including the GNOKII project www.gnokii.org and the GAMMU project (spinoff) http://www.mwiacek.com/ , and may be governed by their applicable GNU licences (though whether these licenses apply to protocol descriptions, I will leave for others to sort out). They are gathered here to hopefully save time, as it took a lot of digging to actually find this information on the web.

Download source code in an124.zip
Download files in an124nokiacode.zip