1. System Software Design
Scrolling Message Display
By: Derek Valleroy

2. Kernel Selection MicroC/OS-II Task Synchronization
Message Passing with Semaphores and Buffers

3. Tasks and ISRs Main Task Startup Task User Interface Task LED Scroll
Creates the startup task.
Startup Task
Initializes peripherals and creates message bitmaps.
User Interface Task
Allows users to change messages, sign intensity, speed, etc.
Uses a PC with a terminal program.
LED Scroll
Continuously updates the Display to give a scrolling effect.
Store String
Stores messages in EEPROM.
SCI Task
Sends messages to the User Interface task.
SCI ISR
Queues data received from the keyboard.

4. Task/ISR Specs Task/ISR Priority Task Type Task Period Task Exec. Time
CPU Load
Average
Peak
Main --
5us
Startup 4
One time through
User Interface 5
Sporadic
10ms ms
(max) (avg.)
2ms
.008 .2
LED Scroll 7
Periodic
20ms
72us
.0036
Store String 8
100ms
18ms us
(max) (avg.)
.00005
.18
SCI task 6
(max) (avg.)
3us
.0003
SCI ISR
.5ms ms
2us
.00006
.004
Total:
.0122
.38

5. Module/Library Description
MessDisp.c
Contains the main source code and User Interface code.
LEDWrite.c
Provides LED drivers with the proper signals.
BasicIO.s12
Used for terminal communication with SCI.
ASCIItoMEM.c
Contains the code for storing messages in EEPROM.
SCI.c
SCI task code and ISR.

6. Module/Library Description
MessDisp.c
The module that is most specific to this project.
Functions: none
Public Data: mssgpntr, speedpntr, intenspntr
Tasks: main(), startup(), UItask()

7. Module/Library Description
LEDWrite.c
Communicates with the LED drivers over the SPI.
Functions: SPIInit(), DriverInit(), LEDWrite()
Data: none
Tasks: LEDScroll()

8. Module/Library Description
BasicIO.s12
Contains routines for SCI communication. (reused code) Source: Todd Morton.
Functions: sci_open(), putstrng(), outcrlf(), getchar()
Data: none
Tasks: none

9. Module/Library Description
ASCIItoMEM.c
Stores messages in EEPROM. Also converts a string of ASCII characters into a bitmap.
Functions: EEPROMInit(), Bitmap() –public
Data: mssgpntr,speedpntr,intenspntr
Tasks: StoreString()

10. Module/Library Description
SCI.c
Takes care of user inputs from a keyboard. An ISR signals an incoming character and the SCItask stores it in a buffer.
Functions: SCIinit()
Data: keychar –public
Tasks: SCItask()

11. Intertask Communications
messpntr
speedpntr
Store String
intenspntr
OSQpend()
SCI ISR
Ready Flag
OSSemPend()
OSSemPost()
OSQpost()
SCI Data
Data
Data
Bitmap()
Ring
Buffer
Message
Bitmap
SCI Task
User Interface Task
messpntr
OSSemPost()
OSSemPend()
Ack
Flag
LED Scroll