ISELFinalProjectInfo

Information about several subjects regarding the ISEL final project.

Linux Kernel

https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.13.5.tar.xz

Linux Device Drivers book

http://lwn.net/images/pdf/LDD3/ldd3_pdf.tar.bz2

sysfs

http://lxr.free-electrons.com/source/Documentation/filesystems/sysfs.txt

What it is:

sysfs is a ram-based filesystem initially based on ramfs. It provides a means to export kernel data structures, their attributes, and the linkages between them to userspace.

sysfs is tied inherently to the kobject infrastructure. Please read Documentation/kobject.txt for more information concerning the kobject interface.

Create entry / attributes

https://godandme.wordpress.com/2011/04/05/how-to-make-a-sysfs-entry/

http://stackoverflow.com/questions/11063719/kernel-modules-parameters-in-sysfs-quick-reaction-for-changes

http://stackoverflow.com/questions/11067262/getting-parent-for-kobject-add

IIO

Adapted from http://wiki.analog.com/software/linux/docs/iio/iio

The Industrial I/O subsystem is intended to provide support for devices that in some sense are analog to digital or digital to analog convertors (ADCs, DACs). Devices that fall into this category are:

SPI

I2C

ARM AT91SAM9260B

http://www.atmel.com/devices/sam9260.aspx

A 210MHz ARM926-based processor with an extensive range of communication peripherals. It embeds FS USB host and device interfaces, a 10/100 Ethernet MAC and an image sensor interface, as well as standard peripherals such as a Multimedia Card Interface (MCI), I2S, USARTs, master/slave SPIs, 16-bit Timers, a TWI and four-channel 10-bit ADC. The external bus interface features controllers for SDRAM and static memories including NAND flash and CompactFlash. The SAM9260 is available in 217-ball LFBGA and 208-pin QFP packages.

Linux4SAM

http://www.at91.com/linux4sam/bin/view/Linux4SAM/WebHome

http://www.at91.com/linux4sam/bin/view/Linux4SAM/GettingStarted

http://www.at91.com/linux4sam/bin/view/Linux4SAM/IioAdcDriver

FXOS8700CQ

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FXOS8700CQ

Freescale’s FXOS8700CQ 6-axis sensor combines industry leading accelerometer and magnetometer sensors in a small 3 x 3 x 1.2 mm QFN plastic package. The 14-bit accelerometer and 16-bit magnetometer are combined with a high-performance ASIC to enable an eCompass solution capable of a typical orientation resolution of 0.1 degrees and sub 5 degree compass heading accuracy for most applications.

Datasheet: http://cache.freescale.com/files/sensors/doc/data_sheet/FXOS8700CQ.pdf

Hello world linux kernel module on Slackware 14

   1 su
   2 cd /usr/src/linux/
   3 mkdir helloWorld
   4 cd helloWorld 
   5 nano  Makefile

obj-m = helloWorld.o
KVERSION = $(shell uname -r)
all:
        make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
        make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

   1 #include <linux/module.h>       /* Required by all modules */
   2 #include <linux/kernel.h>       /* Required for KERN_INFO */
   3 #include <linux/init.h>         /* Required for the macros */
   4 
   5 static int __init helloworld_init(void)
   6 {
   7     printk(KERN_INFO "Hello world\n");
   8 return 0;
   9 }
  10 
  11 static void __exit helloworld_exit(void)
  12 {
  13     printk(KERN_INFO "Bye all.\n");
  14 }
  15 
  16 module_init(helloworld_init);
  17 module_exit(helloworld_exit);
  18 MODULE_LICENSE("GPL");

   1 make clean
   2 make
   3 # tail -f /var/log/messages
   4 insmod helloWorld.ko
   5 dmesg
   6 ls /sys/module # /sys/module/helloWorld should appear
   7 rmmod helloWorld.ko

sysfs sample

Based on https://godandme.wordpress.com/2011/04/05/how-to-make-a-sysfs-entry/

Directory located in /usr/src/linux/sysfs_sample

Makefile

obj-m = sysfs_sample.o
KVERSION = $(shell uname -r)
all:
        make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
        make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

sysfs_sample.c

   1 /*
   2 indent -linux sysfs_sample.c
   3 make clean
   4 make
   5 insmod sysfs_sample.ko
   6 tail /var/log/messages
   7 cat /sys/module/sysfs_sample/sysfs_sample_attrs/first
   8 cat /sys/module/sysfs_sample/sysfs_sample_attrs/second
   9 cat /sys/module/sysfs_sample/sysfs_sample_attrs/operation
  10 echo "asdf" >  /sys/module/sysfs_sample/sysfs_sample_attrs/operation
  11 cat /sys/module/sysfs_sample/sysfs_sample_attrs/operation
  12 dmesg
  13 rmmod sysfs_sample.ko
  14 */
  15 #include <linux/module.h>
  16 #include <linux/kernel.h>
  17 #include <linux/init.h>
  18 #include <linux/fs.h>
  19 #include <linux/slab.h>
  20 /*A struct kobject represents a kernel object, maybe a device or so,
  21 such as the things that show up as directory in the sysfs filesystem.*/
  22 struct kobject *sysfs_sample_kobject;
  23 struct int_attribute {
  24         struct attribute attr;
  25         int value;
  26 };
  27 struct string_attribute {
  28         struct attribute attr;
  29         char value[64];
  30 };
  31 static struct int_attribute first_attribute = {.attr.name = "first",.attr.mode =
  32             0666,.value = 11, };
  33 static struct int_attribute second_attribute = {.attr.name =
  34             "second",.attr.mode = 0666,.value = 22, };
  35 static struct string_attribute operation_attribute = {.attr.name =
  36             "operation",.attr.mode = 0666,.value = "add", };
  37 static struct attribute *sysfs_sample_attributes[] =
  38     { &first_attribute.attr, &second_attribute.attr, &operation_attribute.attr,
  39 NULL };
  40 /*Called when a read is performed on a attribute file in sysfs */
  41 static ssize_t default_show(struct kobject *kobj, struct attribute *attr,
  42                             char *buf)
  43 {
  44         struct int_attribute *intAttr;
  45         struct string_attribute *stringAttr;
  46         printk(KERN_INFO "Show called for kobject %s\n", kobj->name);
  47         printk(KERN_INFO "Attribute name: %s\n", attr->name);
  48         /* convert to proper struct based on name */
  49         if (strcmp("operation", attr->name) != 0) {
  50                 intAttr = container_of(attr, struct int_attribute, attr);
  51                 return scnprintf(buf, PAGE_SIZE, "%d\n", intAttr->value);
  52         } else {
  53                 stringAttr = container_of(attr, struct string_attribute, attr);
  54                 return scnprintf(buf, PAGE_SIZE, "%s\n", stringAttr->value);
  55         }
  56 }
  57 
  58 /*Called when a write is performed on a attribute file in sysfs */
  59 static ssize_t default_store(struct kobject *kobj, struct attribute *attr,
  60                              const char *buf, size_t len)
  61 {
  62         struct int_attribute *intAttr;
  63         struct string_attribute *stringAttr;
  64         printk(KERN_INFO "Store called for kobject %s\n", kobj->name);
  65 
  66         if (strcmp("operation", attr->name) != 0) {
  67                 intAttr = container_of(attr, struct int_attribute, attr);
  68                 sscanf(buf, "%d", &(intAttr->value));   /*convert char to int */
  69                 return sizeof(int);
  70         } else {
  71                 stringAttr = container_of(attr, struct string_attribute, attr);
  72                 sscanf(buf, "%s", stringAttr->value);   /*convert char to char */
  73                 printk(KERN_INFO "Sizeof %d\n", sizeof(stringAttr->value));
  74                 return sizeof(stringAttr->value);
  75         }
  76 }
  77 
  78 static struct sysfs_ops sysfs_sample_operations = {.show = default_show,.store =
  79             default_store, };
  80 static struct kobj_type sysfs_sample_type = {.sysfs_ops =
  81             &sysfs_sample_operations,.default_attrs =
  82             sysfs_sample_attributes, };
  83 /*Called on module initialization */
  84 static int __init sysfsexample_module_init(void)
  85 {
  86         int err = -1;
  87         printk(KERN_INFO "sysfs_sample init called \n");
  88         sysfs_sample_kobject =
  89             kzalloc(sizeof(*sysfs_sample_kobject), GFP_KERNEL);
  90         if (sysfs_sample_kobject) {
  91                 kobject_init(sysfs_sample_kobject, &sysfs_sample_type);
  92                 // if (kobject_add(sysfs_sample_kobject, NULL, "%s", "sysfs_sample")) {
  93                 if (kobject_add
  94                     (sysfs_sample_kobject, &THIS_MODULE->mkobj.kobj, "%s",
  95                      "sysfs_sample_attrs")) {
  96                         err = -1;
  97                         printk(KERN_INFO "sysfs_sample creation failed\n");
  98                         kobject_put(sysfs_sample_kobject);
  99                         sysfs_sample_kobject = NULL;
 100                 }
 101                 err = 0;
 102         }
 103         return err;
 104 }
 105 
 106 /*Called on module exit */
 107 static void __exit sysfsexample_module_exit(void)
 108 {
 109         printk(KERN_INFO "sysfs_sample exit called \n");
 110         if (sysfs_sample_kobject) {
 111                 kobject_put(sysfs_sample_kobject);
 112                 kfree(sysfs_sample_kobject);
 113         }
 114 }
 115 
 116 module_init(sysfsexample_module_init);
 117 module_exit(sysfsexample_module_exit);
 118 MODULE_LICENSE("GPL");

RTC device info

https://www.kernel.org/doc/Documentation/rtc.txt

The interrupts are reported via /dev/rtc (major 10, minor 135, read only character device)

The alarm and/or interrupt frequency are programmed into the RTC via various ioctl(2) calls as listed in ./include/linux/rtc.h

The sysfs interface under /sys/class/rtc/rtcN provides access to various rtc attributes without requiring the use of ioctls.

The ioctl() calls supported by /dev/rtc are also supported by the RTC class framework.

Sysfs support

From https://coherentmusings.wordpress.com/2014/02/19/adding-sysfs-support-to-a-driver/

As the Linux Kernel Development book mentions "The sysfs file system is currently the place for implementing functionality previously reserved for ioctl() calls on device nodes or the procfs filesystem"

ARM Cross compiling

https://www.ailis.de/~k/archives/19-ARM-cross-compiling-howto.html

http://frank.harvard.edu/~coldwell/toolchain/

Based on gcc and glibc used on the embedded device

http://preshing.com/20141119/how-to-build-a-gcc-cross-compiler/

http://xathrya.web.id/blog/2013/02/28/building-gcc-arm-toolchain-on-slackware64/

With emdebian Ubuntu lucid32

   1 nano /etc/apt/sources.list
   2 apt-get update
   3 apt-get install linux-libc-dev-armel-cross libc6-armel-cross  libc6-dev-armel-cross binutils-arm-linux-gnueabi  gcc-4.4-arm-linux-gnueabi
   4 apt-get install g++-4.4-arm-linux-gnueabi
   5 apt-get install pdebuild-cross
   6 apt-get install dpkg-cross qemu
   7 cd /tmp
   8 wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.13.5.tar.xz
   9 tar xvif linux-3.13.5.tar.xz
  10 mv linux-3.13.5 /usr/src
  11 /usr/src/
  12 cd /usr/src
  13 ln -s linux-3.13.5 linux
  14 ls
  15 cd linux
  16 make ARCH=arm at91sam9260_9g20_defconfig # copy config for ARM at91sam9260
  17 make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
  18 export ARCH=arm
  19 export CROSS_COMPILE=arm-linux-gnueabi-
  20 export INSTALL_MOD_PATH=/lib/modules/arm/3.13.5/
  21 make modules 
  22 find . -name "*.ko" | xargs -i file {}
  23 make modules_install # to /tmp/lib ....
  24 mkdir  -p /usr/src/linux/helloWorld
  25 cd /usr/src/linux/helloWorld

Makefile

obj-m = helloWorld.o
KVERSION=3.13.5
all:
        make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
clean:
        make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

helloWorld.c

   1 #include <linux/module.h>       /* Required by all modules */
   2 #include <linux/kernel.h>       /* Required for KERN_INFO */
   3 #include <linux/init.h>         /* Required for the macros */
   4 
   5 static int __init helloworld_init(void)
   6 {
   7     printk(KERN_INFO "Hello world\n");
   8 return 0;
   9 }
  10 
  11 static void __exit helloworld_exit(void)
  12 {
  13     printk(KERN_INFO "Bye all.\n");
  14 }
  15 
  16 module_init(helloworld_init);
  17 module_exit(helloworld_exit);
  18 MODULE_LICENSE("GPL");

   1 cd helloWorld
   2 make clean
   3 make

Simple hello ARM

   1 lsb_release -a
   2 #No LSB modules are available.
   3 #Distributor ID: Ubuntu
   4 #Description:    Ubuntu 10.04.4 LTS
   5 #Release:        10.04
   6 #Codename:       lucid
   7 
   8 arm-linux-gnueabi-gcc --version
   9 #arm-linux-gnueabi-gcc (Debian 4.4.5-8) 4.4.5
  10 

hello.c

   1 #include <stdio.h>
   2 
   3 int main()
   4 {
   5     printf("Hello cross-compiling world!\n");
   6     return 0;
   7 }

   1 arm-linux-gnueabi-gcc -static hello.c -o hello
   2 qemu-arm -cpu arm926 hello
   3 # Hello cross-compiling world!
   4 
   5 arm-linux-gnueabi-gcc  hello.c -o hello
   6 qemu-arm -L /usr/arm-linux-gnueabi/ hello
   7 # Hello cross-compiling world!
   8 file hello
   9 #hello: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, not stripped
  10 
  11 export ARCH=arm
  12 export CROSS_COMPILE=arm-linux-gnueabi-
  13 export INSTALL_MOD_PATH=/lib/modules/arm/3.13.5/
  14 cd /usr/src/linux/helloWorld/

helloworld.c

   1 #include <linux/module.h>       /* Required by all modules */
   2 #include <linux/kernel.h>       /* Required for KERN_INFO */
   3 #include <linux/init.h>         /* Required for the macros */
   4 
   5 static int __init helloworld_init(void)
   6 {
   7     printk(KERN_INFO "Hello world\n");
   8     return 0;
   9 }
  10 
  11 static void __exit helloworld_exit(void)
  12 {
  13     printk(KERN_INFO "Bye all.\n");
  14     return;
  15 }
  16 
  17 module_init(helloworld_init);
  18 module_exit(helloworld_exit);
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("DonaldDuck");

   1 make clean
   2 make
   3 scp helloworld.ko root@192.168.1.100:/tmp
   4 # on embedded system
   5 insmod helloworld.ko 
   6 dmesg # should show an hello world
   7 rmmod -f helloworld

Hard iron interference calibration

   1 '''
   2 Based on the worked example 1 from AN4246 - Freescale
   3 Calibrating an eCompass in the Presence of Hard and Soft-Iron Interference
   4 http://www.freescale.com/files/sensors/doc/app_note/AN4246.pdf
   5 
   6 http://en.wikipedia.org/wiki/Earth's_magnetic_field
   7 Its magnitude at the Earth's surface ranges from 25 to 65 microtesla (0.25 to 0.65 gauss). 
   8 
   9 The tesla is the SI unit of the Magnetic field, B.
  10 
  11 '''
  12 import numpy as np
  13 import math
  14 import unittest
  15 
  16 def calculateBeta(measuresA):
  17     measures=np.array(measuresA)
  18     #print '# Measures #'
  19     #for i in measures: print i
  20     yMatrix=[]
  21     #calculate squares for each item
  22     for m in measures: yMatrix.append( (m[0]*m[0]) +(m[1]*m[1]) + (m[2]*m[2])  )
  23     yMatrix=np.array(yMatrix)
  24     #print '# Y matrix #'
  25     #for i in yMatrix: print i
  26     xMatrix=[]
  27     for m in measures: xMatrix.append( [m[0],m[1],m[2],1]  )
  28     xMatrix=np.array(xMatrix)
  29     #print '# X Matrix #'
  30     #for j in xMatrix: print j
  31     #print "beta = ( X' * X )^-1  * X'*Measures "
  32     transposeX = np.matrix.transpose( xMatrix )
  33     #print '# X Matrix transpose#'
  34     #for j in transposeX: print j
  35     r1 = np.dot(transposeX , xMatrix)
  36     #print "r1\n%s"%(r1)
  37     inv1 = np.linalg.inv(r1)
  38     #print "inv1\n%s"%(inv1)
  39     r2 = np.dot(inv1,transposeX)
  40     #print "r2\n%s"%(r2)
  41     beta = np.dot(r2,yMatrix)
  42     #print "beta\n%s"%(beta)
  43     #vx = beta[0]*0.5
  44     #vy = beta[1]*0.5
  45     #vz = beta[2]*0.5
  46     #print " %f %f %f"%(vx, vy , vz)
  47     #B = math.sqrt( (beta[3]) + (vx*vx) + (vy*vy) + (vz*vz)  )
  48     #print "%f uT"%(B)
  49     #return B
  50     return beta
  51 ########################################################################
  52 
  53 class SimpleTestCase(unittest.TestCase):
  54     def testCalculation(self):
  55         # the norm of the vector should be between 25 and 65
  56         #acquired magnetometer measures
  57         measures=[]
  58         measures.append([167.4 , -242.4 ,91.7])
  59         measures.append([140.3 , -221.9 ,86.8])
  60         measures.append([152.4 , -230.4 ,-0.6])
  61         measures.append([180.3 , -270.6 ,71.0])
  62         measures.append([190.9 , -212.4 ,62.7])
  63         measures.append([192.9 , -242.4 ,17.1])
  64         Beta = calculateBeta(measures)
  65         #print "%s "%(Beta)
  66         vx = Beta[0]*0.5
  67         vy = Beta[1]*0.5
  68         vz = Beta[2]*0.5
  69         # subtract V from the measures ...
  70         for m in measures:
  71             # subtract the strong iron effect from the raw measure
  72             vector=[m[0]-vx,m[1]-vy,m[2]-vz]
  73             normVector = np.linalg.norm( vector )
  74             self.assertTrue( normVector>= 25 and normVector <=65 )
  75             self.assertTrue( normVector>= 47 and normVector <48 )
  76         
  77 if __name__=='__main__':
  78     unittest.main()

Build GSL for ARM on emdebian

   1 mkdir -p /usr/local/arm
   2 cp gsl-1.16.tar.gz /tmp
   3 cd /tmp
   4 tar xvzf gsl-1.16.tar.gz 
   5 cd gsl-1.16
   6 ./configure --prefix=/usr/local/arm --exec-prefix=/usr/local/arm CC=arm-linux-gnueabi-gcc --host armv5 --target arm-linux-gnueabi
   7 make clean; make; make install

Vagrant, change Vagrantfile to SSH listen on 0.0.0.0

Change Vagrantfile

config.vm.network :forwarded_port, guest: 22, host: 2222, host_ip: "0.0.0.0", id: "ssh", auto_correct: true

GSL, blas example

Matrices multiplication

   1 /*
   2  cc blasExample.c -o blasExample -lgsl -lgslcblas
   3  cc blasExample.c -o blasExample -lgsl -lgslcblas -lm -static
   4 
   5  on emdebian 
   6  arm-linux-gnueabi-gcc blasExample.c -o blasExample -lgsl -lgslcblas -lm -I/usr/local/arm/include/ -L/usr/local/arm/lib/ -L/usr/arm-linux-gnueabi/lib
   7  arm-linux-gnueabi-gcc blasExample.c -o blasExample -lgsl -lgslcblas -lm -I/usr/local/arm/include/ -L/usr/local/arm/lib/ 
   8 
   9  arm-linux-gnueabi-gcc blasExample.c -o blasExample -lgsl -lgslcblas -lm -I/usr/local/arm/include/ -L/usr/local/arm/lib/ -static
  10  qemu-arm blasExample
  11 */
  12 #include <stdio.h>
  13 #include <gsl/gsl_blas.h>
  14 
  15 int
  16 main (void)
  17 {
  18   double a[] = { 0.11, 0.12, 0.13,
  19                  0.21, 0.22, 0.23 };
  20 
  21   double b[] = { 1011, 1012,
  22                  1021, 1022,
  23                  1031, 1032 };
  24 
  25   double c[] = { 0.00, 0.00,
  26                  0.00, 0.00 };
  27 
  28   gsl_matrix_view A = gsl_matrix_view_array(a, 2, 3);
  29   gsl_matrix_view B = gsl_matrix_view_array(b, 3, 2);
  30   gsl_matrix_view C = gsl_matrix_view_array(c, 2, 2);
  31 
  32   /* Compute C = A B */
  33 
  34   gsl_blas_dgemm (CblasNoTrans, CblasNoTrans,
  35                   1.0, &A.matrix, &B.matrix,
  36                   0.0, &C.matrix);
  37 
  38   printf ("[ %g, %g\n", c[0], c[1]);
  39   printf ("  %g, %g ]\n", c[2], c[3]);
  40 
  41   return 0;  
  42 }

ARM GPIO, General Purpose Input/Output

ISELFinalProjectInfo (last edited 2023-05-26 15:24:57 by 127)