"RTOS2" Project

The following application is one that I have implemented quite a few times for different books. It is actually quite a good one to demonstrate the operation of an RTOS.

Click Here to look at the PICmicro MCU source code.

The circuits used for this application are:

The bill of materials for this application is listed in the table below.

Part Description

PIC18C452 PIC18C452-JW

4 MHz 4 MHz Ceramic Resonator with Internal Capacitors

10K 3x 10K, 1/4 Watt Resistors

10K Pot 10K, Single Turn Potentiometer

0.1 uF 0.1 uF, 16 Volt Tantalum Capacitor

Button Momentary On Push Button

LCD 16x2, Hitachi 44780 based LCD

Miscellaneous Prototyping Card, Wiring, +5 Volt Power Supply

The RTOS Template code can be accesseed by clicking Here.

The RTOS system requests are listed in the table below:

RTOS Request Input Output Macro

Start Task - Starting Address
- Priorty
- File Register Size Requirements - Carry Reset, OK and New Task Number in "WREG"
- Carry Set, NO Available Tasks or more than 63 Task Variables Requested TaskStart Address, Priority, Size
Address, Priority and Size are all constants

Next Task None None TaskNext

Wait for Interrupt - Interrupt Number None IntWait Interrupt
Interrupt is a Constant

Send Message - Task Number
2 Byte Message in FSR0L/FSR1L None MsgSend TaskNumber
TaskNumber is a Variable

Wait for Message None - 2 Byte Message in FSR0L/FSR1L
TaskNumber in WREG MsgWait

Read Message - Task Number - Carry Reset 2 Byte Message in FSR0L/FSR1L
- Carry Set, no message to receive MsgRead TaskNumber
TaskNumber is a Variable

Ack Message - Task Number - Carry Reset Operation Complete
- Carry Set, no message to acknowledge MsgRead TaskNumber
TaskNumber is a Variable

The Interrupt List and Numbers are:

Interrupt Number Interrupt Source Register Location

0 TMR1 PIR1

1 TMR1 PIR1

2 CCP1 PIR1

3 SSP PIR1

4 USART TX PIR1

5 USART RX PIR1

6 AD PIR1

7 PSP PIR1

8 CCP2 PIR2

9 TMR3 PIR2

10 LVD PIR2

11 BCL PIR2

12 RB INTCON

13 INT0 INTCON

14 TMR0 (16.384 msec delay) INTCON

15 Not Avaliable Used by the RTOS