There are many uses for an RS232 port, but I am most interested in it for debugging. The master console can be directed to the RS232 port using the console kernel parameter. This will hopefully make it easier to debug kernel problems.
Under the SIM card there is an 11 contact interface. Three of the contact are for the RS232 port.
rs232_1.JPG 38.96KB 992 downloads
What you will need.
- A 3V RS232 adapter. Most PC RS232 ports are 5V, do not hook that up directly to the phone. The are many options here, I used one of these, but there are many other choices. The FTDI USB solutions appear to be well supported, but a MAX232 based serial converter would also work and should be a bit cheaper.
- Some wire. You want fairly small single core wire. I used 30awg because I have a spool of it, but a bit bigger would be fine.
- Soldering iron.
- An RS232 console application. I'm using minicom on linux, but there are heaps of alternatives on all platforms. I think PuTTY does RS232, so if your on windows take a look at that.
Pin-out ======= 1 2 3 4 5 6 7 8 9 10 11 4=TX 10=RX 11=GND Connections =========== Phone --- PC adapter GND --- GND RX --- TX TX --- RXrs232_2.JPG 60.71KB 965 downloads
Red = TX
Green = RX
Blue = GND
Cut some wires. The shorter the better. The longer the wires the greater the chance of interference.
Connect TX on the phone to RX on the RS232 adapter.
Connect RX on the phone to TX on the adapter.
Connect GND to GND. It will work without GND connected, but you will probably get more noise.
I recommend soldering, but you could try tape or hot glue if you don't want to solder on the board. Unfortunitely this isn't very good if you actually use your phone.
I needed to use a bit of flux to get the solder to stick on the board.
rs232_3.JPG 57.04KB 970 downloads rs232_4.JPG 82.68KB 970 downloads
rs232_5.JPG 101.16KB 965 downloads
All done. Now connect it to your PC.
Configuring the PC
First, figure out what your comm port is called and if needed install drivers. The FT232R doesn't need any drivers in linux (as long as right driver is in the kernel) and appears as /dev/ttyUSB0.
Now start your console software. You will need to configure the port.
The setting you want are 9600 8N1, no hardware or software flow control.
Connect with the console software
On the phone run
echo Hello > /dev/ttyMSM2You should see 'Hello' appear in the console on the PC.
Next, on the phone run
cat /dev/ttyMSM2Now enter 'Hello' in the console on the PC and press enter. You should see 'Hello' displayed in the phones shell.
If that all worked you now have a working RS232 port.