This document describes a project to control a 2-axis stepping motor platform using a Raspberry Pi single-board computer running Xenomai. A kernel module and userspace program were developed to control two 42-type stepper motors connected to A4988 motor driver boards via the Raspberry Pi's GPIO pins. The platform measures 45 by 40 cm and each motor step is 1.8 degrees. Xenomai was used to provide real-time control of the motors by modifying the Linux kernel and enabling hard real-time capabilities.

1. TEACHER：張大緯 老師
TEAM：1
MEMBER：陳冠宇、傅翔祺、胡浩晟、周佳惠
103 IODD Project Report
Based on Raspberry Pi with the
application of stepper
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2. Agenda
Result Architecture
Method
• Control Motor
• Xenomai
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3. Result
•A application program to control the
device via library “bcm2835”
•A kernel module
•2-axis platform
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5. Architecture
•Controller
• Raspberry Pi Model B (BCM2835、BCM2708、ARM1176JZ-F)
• Xenomai-3
•Device
• 42 type Stepper Motor * 2
• A4988 Stepper motor drive board *2
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6. Architecture
•Controller
•A4988
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7. Architecture
•2-axis platform
•45 * 40 (cm2)
•Motor : 1.8o per step
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8. Method
•Controller
•Library “bcm2835”
• bcm2835_gpio_fsel()
• bcm2835_gpio_write()
• bcm2835_gpio_lev()
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9. Method
•Controller
•Modify context to control peripheral
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10. Method
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11. Method
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12. Method
void Position(int x, int y, char type);
//Move length(unit)
void Move_len(int len, int dir, int motor);
void Init_home();
Start
Moving to specify
position
Initialization
12
End
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13. Method
「We are engineers from a wide background collaborating in the
open to offer the most adequate options for running real-time
applications on embedded Linux© platforms.」 Ref. Xenomai.org
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14. Method
Cobalt Architecture
Mercury Architecture(Xenomai-2 use)
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15. Method
The linux kernel
Xenomai source code
Cross-Compiler 4.8.3
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16. Method
1. Patch “ipipe-core-3.18.12-arm-1”
2. Modify(Detail in [5])
• Kconfig
• bcm2708.c
• bcm2708_gpio.c
• spi-bcm2708.c
3. $make ARCH=arm O=build CROSS_COMPILE=… menuconfig
4. Set option from “*” to “n”
• CONFIG_CPU_FREQ
• CONFIG_CPU_IDLE
• CONFIG_KGDB
• CONFIG_CONTEXT_TRACKING_FORCE
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17. Method
5. Compile the source code and create image file
6. $make –j8 ARCH=arm O=build CROSS_COMPILE=$...
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18. Method
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19. Method
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20. Reference
1. NCKU Wiki Xenomai
http://wiki.csie.ncku.edu.tw/embedded/xenomai
2. Emp learning in blogger
3. Emp learning in Hackpad
https://emp-learn.hackpad.com/Beaglebone-black-learn.-mZ2XeVZLECp
4. GPIO Sysfs Interface for Userspace
https://www.kernel.org/doc/Documentation/gpio/sysfs.txt
5. The patch of raspberry pi
https://git.xenomai.org/xenomai-2.6.git/tree/ksrc/arch/arm/patches/raspberry/ipipe-core-3.8.13-
raspberry-post-2.patch
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