Stellaris® Robotic Evaluation
Board and Micriµm µC/OS-III
Dexter Travis, Stellaris ARM® Cortex™-M3 Applications Engineering
Jean J. Labrosse, Founder, President and CEO of Micriµm
1
Introductions
•Jean J. Labrosse
–Founder, President and CEO of Micriµm
•Dexter Travis
–Stellaris® ARM® Cortex™-M3 Applications Engineering
2
Find the right ARM® Solution for you
32-bit ARM
MCU for
Safety-Critical
Applications
32-bit ARM
Cortex™-M3
MCUs
ARM
Cortex-A8 &
ARM9™ MPUs
TMS570
Stellaris®
Sitara™
ARM
Cortex-R4™
ARM Cortex-M3
Up to 250 DMIPS/
160 MHz
Up to
80 MHz
375MHz to
>1GHz
2 MB Flash,
160 KB RAM
Flash
8 KB to 256 KB
USB, ENET
MAC+PHY CAN,
ADC, PWM, SPI
Connectivity,Security,
Motion Control, HMI,
Industrial Automation
Cache,
RAM, ROM
300MHz to >1Ghz
+Accelerator
Cache
RAM, ROM
USB, CAN, SATA,
SPI, PCIe, EMAC
USB, ENET,
PCIe, SATA, SPI
Industrial automation,
POS & portable
data terminals
$1.00 to $8.00
$5.00 to $25.00
Floating/Fixed Point
Video, Audio, Voice,
Security, Conferencing
$5.00 to $200.00
ARM Cortex-A8
& ARM9
DSP
DSP+ARM
C6000™
Integra™
DaVinci™
Digital Media processors
FPU, ECC, Timer/PWM
Co-Proc, 12bit ADCs, CAN,
EMIF, LIN, SPI, Flexray
Transportation, Motor
Control, Certified for use in
safety critical (SIL3) systems
$7.00 to $18.00
Responsive design support
Development tools
Software support
Comprehensive developer ecosystem
Agenda
• RTOSs and Real-Time Kernels
– A brief introduction
• Micriµm - µC/OS-III
–
–
–
–
–
Summary of features
Scheduling and Context Switching
Synchronization
Message Passing
Other Services
• Texas Instruments - EVALBOT
– Features
– Examples
– Demo
RTOS vs Real-Time Kernels
Application
Keyboard
Keyboard
Controller
Graphical
User
Interface
Display
Controller
Touch Screen
Controller
Interrupt
Controller
Timer
Real-Time
Kernel
RTOS
(MAC/PHY)
TCP/IP
Stack
TCP/IP
Apps
File
System
Media
Controller
Audio
I2S
Controller
CAN
CAN
Controller
Modbus
RS-232C
RS-485
Other
USB
(Host)
(Device)
USB
Stacks
© 2010, Micriµm, All Rights Reserved
(Shell)
(Clk)
(CRC)
(etc.)
Touch Interface
Media
CPU
Ethernet
Controller
Display
with optional
www.Micrium.com
(SD)
(MMC)
(NAND Flash)
(NOR Flash)
(CF)
(RAM Disk)
Other
What is a Real-Time Kernel?
 Software that manages the time of a CPU
 Performs multitasking
– ‘Switches’ the CPU between tasks
– Highest priority task runs on the CPU
– Round-robins tasks of equal priority
 Provides valuable services to an application:
–
–
–
–
–
–
–
–
Task management
Synchronization
Mutual exclusion management
Message passing
Memory management
Time management
Soft-timer management
Other
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
What is a Real-Time Kernel?
High Priority Task
Task
Task
Importance
Task
Each Task
Task
Task
Task
Low Priority Task
© 2010, Micriµm, All Rights Reserved
Event
Event
Task
Task
Infinite Loop
Task
www.Micrium.com
Preemptive Kernels
Via a kernel call, the ISR makes
the high priority task ready
Interrupt occurs
ISR
ISR completes and
the kernel switches
to the high-priority
task
ISR
High-priority task
The kernel switches
to the low-priority
task
Low-priority task
Time
© 2010,
All Rights Reserved
© 2009,
Micriµm,Micriµm,
All Rights Reserved
www.Micrium.com
www.Micrium.com
What is µC/OS-III?
 A third generation Real-Time Kernel
– Has roots in µC/OS-II, the world’s most popular Real-Time Kernel
 µC/OS-II’s internals were described in the book: “MicroC/OS-II, The Real-Time Kernel” (1998)
 A new 850+ page book:
– “µC/OS-III, The Real-Time Kernel”
– Describes µC/OS-III’s internals
– The book comes with:
 A Cortex-M3 based evaluation board
– Featuring TI’s LM3S9B92
 Links to download:
– Sample code to run µC/OS-III
– IAR’s 32K KickStart tools
– A trial version of µC/Probe
– Companion EVALBOT
 5 Example projects
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
µC/OS-III
Summary of Key Features
 Preemptive Multitasking
– Round-robin scheduling of equal-priority tasks
 ROMable
 Scalable
– Adjustable footprint
– Compile-time and run-time configurable
 Portable
– All µC/OS-II ports can be adapted to µC/OS-III
 Rich set of services
– Task Management, Time Management, Semaphores, Mutexes, Message
Queues, Soft Timers, Memory Management, Event Flags and more
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
µC/OS-III
Summary of Key Features
 Real-Time, Deterministic
– Reduced interrupt and task latency
 Built-in Performance Measurement
–
–
–
–
–
Measures interrupt disable time on a per-task basis
Measures stack usage for each task
Keeps track of the number of context switches for each task
Measures the ISR-to-Task and Task-to-Task response time
And more
 Cleanest source code in the industry
 Consistent API
 Run-Time argument checking
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Typical µC/OS-III Tasks
void
{
}
MyTask (void *p_arg)
Do something with ‘argument’ p_arg;
Task initialization;
for (;;) {
Wait for event;
/* Time to expire ...
/* Signal/Msg from ISR ...
/* Signal/Msg from task ...
/* Processing (Your Code)
}
*/
*/
*/
*/
Variables
Arrays
Structures
CPU
Registers
Task
(Priority)
Stack
(RAM)
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
I/O
Devices
(Optional)
‘Creating’ a Task
 You create a task by calling a service provided by the
kernel:
Task Control Block
OSTaskCreate(OS_TCB
CPU_CHAR
OS_TASK_PTR
void
OS_PRIO
CPU_STK
CPU_STK
OS_STK_SIZE
OS_MSG_QTY
OS_TICK
void
OS_OPT
OS_ERR
© 2010, Micriµm, All Rights Reserved
*p_tcb,
*p_name,
p_task,
*p_arg,
prio,
*p_stk_base,
*p_stk_limit,
stk_size,
q_size,
time_slice,
*p_ext,
opt,
*p_err);
www.Micrium.com
Task Name
Task Start Address
Priority
Stack
Stack Limit
Stack Size
Time Slice
Options
The µC/OS-III Scheduler
Using Count Leading Zeros (CLZ)
 The Cortex-M3 has a CLZ instruction
– Makes scheduling much faster … ex. with 64 priorities
ReadyTbl[]
0
31
[0]
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
[1]
0
0
0
0
0
1
1
0
1
1
1
1
0
1
1
1
32
63
Ready Priority = 37
if (ReadyTbl[0] == 0)
Prio = CLZ(ReadyTbl[1]) + 32;
else
Prio = CLZ(ReadyTbl[0]);
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
#Zeros
32
5
The µC/OS-III Ready List
Highest Priority
Multiple Tasks
At
Same Priority
Lowest Priority
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Context Switch
ARM Cortex-M3 for µC/OS-III
 (1): Current task’s CPU
registers are saved on
current task’s stack
 (2): CPU’s SP register
is saved in current
task’s TCB
 (3): New task’s SP is
restored from the new
task’s TCB
 (4): CPU registers are
restored from the new
task’s stack
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Resource Management
(Mutual Exclusion Semaphore)
Delta TS
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Synchronization
(Semaphores)
Delta TS
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Synchronization
(Event Flags)
Delta TS
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Message Passing
(Message Queues)
Delta TS
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
Other µC/OS-III Features
 Task Management
– Suspend/Resume a task
– Delete a task
 Time Management
 Software Timers
 Fixed-Size Memory Partitions
 Pending on Multiple Objects
 And more.
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
µC/Probe
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
What is µC/Probe?
 ‘Windows’ application to display/change target data:
– ANY variable
– ANY memory location
– ANY I/O port
 Works with ANY processor
– 8-, 16-, 32-, 64-bit or DSP
 Works with ANY compiler
– Compiler/linker needs to generate an ELF/DWARF file such as Embedded
Workbench
 Supports many interfaces
–
–
–
–
–
–
RS-232C
USB
TCP/IP (Ethernet)
J-Link
SWD (Cortex-M3) … NO target resident coded needed!
Others
 Target doesn’t need an RTOS
– Works with or without an RTOS
© 2010, Micriµm, All Rights Reserved
www.Micrium.com
µC/Probe
µC/OS-III Task Awareness
Task
Name
Task
Priority
Max Interrupt
Disable Time
© 2010, Micriµm, All Rights Reserved
% CPU
Usage
Stack
Usage
#Context
Switches
ISR to Task
Response
www.Micrium.com
To run the book examples
… you will need:
• The µC/OS-III book
• The TI EVALBOT
– http://www.ti.com/evalbot
• Download and install the IAR 32K edition of Embedded Workbench for
the ARM (V5.5)
– http://supp.iar.com/Download/SW/?item=EWARM-KS32
– You will need to install the J-Link driver
• Download and unzip the µC/OS-III book examples:
– http://www.Micrium.com/Books/Micrium-uCOS-III
• Download and install the non-time limited TRIAL version of µC/Probe:
– http://www.Micrium.com/Books/Micrium-uCOS-III
Texas Instruments EVALBOT unassembled
26
Texas Instruments EVALBOT
Bumpers
(2)
User Switches
(2)
Speaker
Stellaris
LM3S9B92
USB-Device
Connector
USB-Host
Connector
96x6 OLED
Display
RJ45 10/100
Ethernet
ON/OFF
Switch
MicroSD
Socket
Motor/Wheel
(2)
In-Circuit
Debug Interface
Batteries
(3 AA)
Examples
• Example 1: Simple Display
– Rotates a series of messages on the Display
– Blinks LEDS on the board
• Example 2: Using Audio
– Bump sensors select next or previous wav track
– SWITCH2 begins audio playback, SWITCH1 stops playback
• Example 3: Simple Control
– Manual start/stop of the motor via SWITCH1, SWITCH2 and bump sensors
• Example 4: Autonomous Control
– EVALBOT moves randomly and reacts to sensor inputs.
28
Autonomous EVALBOT Control
Control Task queues
commands to motor tasks
If Timer expires a random
turn is initiated
Motor Tasks receives
command, interprets and
posts to PID Task
PID Task closes motor
control loop based on
feedback from speed sensor
interrupt handlers
Input Monitor Task posts
flags to Control Task
speed sensor interrupts relay
data back to PID Task
buttons and Bump Sensor
trigger Input monitor task
29