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Milestone 0: Familiarisation

This is a simple exercise designed to get you started on L4. It contains very detailed instructions, together with the existing source code and the L4 manual you should have no problem doing it.

• Get yourself a copy of the skeleton SOS.
• Build and run the example.
  1. tar zxvf sos.tar.gz
  2. cd sos
  3. make
  4. This should create /tftpboot/sos.$USER
• The example skeleton operating system includes an application tty_test which starts up, prints out its thread id, and then goes into a loop.
• The example includes a printf implementation that outputs data to L4's debug console. In fact it uses the provided l4e_print_string function. This function should only be used for internal SOS debugging, not as a console for applications, so, your task is to modify the printf function to send data to the other serial port.

The second part of milestone zero is to find a partner for the rest of the project. The project is to be completed unless prior permission has been obtained from the LiC.

Recommended procedure

1. Read (and understand) the code in sos/main.c and the code in the tty_test application.
2. Read the documentation on libserial.
3. Design an IPC protocol to transfer data from the user program to your operating system.
4. Write a client side implementation called tty_send_string (or similar) in ttyout.c.
5. Change the syscall_loop in main.c to handle recognise your new protocol, and print out a debug message when you receive one of these messages.
6. Edit tty_test.c so that it tests your tty_send_string function.
7. Change the server side so that it now prints the data to the serial port.
8. Change the implementation of printf to use your new tty_send_string function.
9. Test that all of tty_test's output now goes to the second serial line, not the console debugger.

Assessment

You will need to demonstrate your solution, running on the U4600 hardware to the tutor during the demonstration period. You should be prepared to show your tutor which files you modified in your solution, and explain any design decisions you made.

You will let the tutor know who your partner is so that group accounts can be created for you.