5 An Application

5.1Introduction

In this chapter, we present a simple application: a monitor program that receives commands from a serial port, executes them, and prints the result on the same serial port. The commands are mainly concerned with retrieving information about the running system, such as the status of tasks, or the memory used. This monitor has shown to be quite useful in practice, so it is recommended to include it in any application. In order to use the monitor, a terminal or a computer running a terminal emulation, for example the kermit program, is connected to the serial port used by the monitor.

5.2Using the Monitor

The monitor supports a collection of commands that are grouped in menus: the main menu, the info menu, the duart menu, the memory menu, and the task menu. Other menus can easily be added if required. The only purpose of the main menu is to enter one of the other menus.

Main

Menu

Command

Command

Command

Command

Command

FIGURE 5.1 Monitor Menu Structure

In each menu, the monitor prints a prompt, such as “ Main >” when the monitor is ready to accept a command. A command consists of a single character and, for some commands, of an additional argument. Some commands may be activated by different characters (e.g. H or ? for help), and commands are not casesensitive. It is not possible to edit commands or arguments.

The two commands shown in Table 1 are valid for all menus:

TABLE 1. Commands available in all menus

The remaining commands shown in Table 2 are only valid in their specific menus.

TABLE 2. Specific commands

5.3A Monitor Session

The commands of the monitor are best understood by looking at a commented monitor session. Commands and arguments entered are shown in bold font. When the monitor is started, it prints a start-up message:

Monitor started on channel 1.

Type H or ? for help.

Main Menu [D I M T H]

Main >

H (or ?) shows the options available in the (main) menu:

Main > h

D enters the duart menu and h shows the options available:

Main > d

Duart Menu [B C M T H Q]

Duart_A > ?

B - Set Baud Rate

C - Change Channel

M - Change Mode

T - Transmit Character

B sets the baud rate of the duart channel A (SERIAL_0), M sets the data format. The monitor itself is running on SERIAL_1 so that this setting does not disturb the monitor session.

Duart_A > b

Baud Rate ? 9600

Duart_A >

Duart_A > m

Data Bits (5-8) ? 8

Parity (N O E M S) ? n

Databits = 8 / Parity = n set.

C toggles the duart channel, which changes the prompt of the duart menu.

Duart_A > c

Duart_B >

T transmits a character. The character is entered in hex (0x44 is ASCII ’D’).

Duart_B > t 44

Sending 0x44D

Duart_B >

The last character (’D’) in the line above is the character transmitted. Q exits the duart menu and i enters the info menu.

Duart_B > q

Main > i

Info > ?

O - Overflows

S - System Memory

T - System Time

Info Menu [O S T H Q]

O displays the overflows of the serial input queues.

S displays the top of the system RAM used. Since the RAM is starting at address 0x20000, the total amount of RAM required is slightly more than 4 kBytes:

Info > s

Top of System Memory: 20001050

T shows the time since system start-up in milliseconds (i.e. 23 seconds) and q leaves the info menu.

Info > t

System Time: 0:23140

Info > q

M enters the memory menu and h shows the available options.

Main > m

Memory Menu [D H Q]

Memory > h

D - Dump Memory

D dumps the memory from the address specified. The memory dump may be continued after the last address by typing return (not shown). Here, the address is 0; thus dumping the vector table at the beginning of crt0.S. Q leaves the memory menu.

T enters the task menu and h shows the available options.

Main > t

Task Menu [P S T H Q]

Task > h

P - Set Task Priority

S - Show Tasks

T - Show Task

S displays a list of all tasks. The current task is marked with an arrow:

Task > s Show Tasks:

----------------------------------------------------

TCB Status Pri TaskName ID US Usage

----------------------------------------------------

====================================================

T shows details of a particular task. The task number entered is the position of the task in the display of the previous command, starting at 0, rather than the task ID. Thus entering 1 displays the idle task rather than the monitor task.

Apparently the user stack of 512 bytes for the idle task could be reduced to 160 bytes. Finally, p sets the monitor task priority and q returns to the main menu:

Task > p Set Task Priority:

Task number = 0

Task priority = 200

Set Monitor Task Priority to 200

Task >

Task > q

Main >

In some cases, an additional prompt is printed after having entered numbers. The function accepting numbers waits until a non-digit, such as carriage return, is entered. If this carriage return is not caught, then it is interpreted as a command. Except for the memory menu, carriage return is not a valid command; it is ignored and a new prompt is displayed.