Archive for July, 2015

SCHED_DEADLINE realtime scheduling in Linux

This is best explained by the article:

Realtime framework in Android:

Back to school: Learning security in Linux: old and new stuff

Linux Security: Securing and Hardening Linux Production Systems

And Ubuntu has a matrix to show its security features:

Seccomp and Sandboxing:

“What the Chrome developers would like is a more flexible way of specifying which system calls can be run directly by code inside the sandbox.One suggestion that came out was to add a new “mode” to seccomp. The API was designed with the idea that different applications might have different security requirements; it includes a “mode” value which specifies the restrictions that should be put in place. Only the original mode has ever been implemented, but others can certainly be added. Creating a new mode which allowed the initiating process to specify which system calls would be allowed would make the facility more useful for situations like the Chrome sandbox.”

Bypassing module_disabled functionality (disabling kernel modules loading):

Ultrasonic sensor + Arduino programming

After purchasing this ultrasonic sensor (JSN-SR04T):

I have got some problem understanding the specs and programming it. After some experimentation, and reading up Arduino’s version of the solution:

The following is the outcome:

unsigned long echo = 0;
int ultraSoundSignal = 9; // Ultrasound signal pin
int ultraSoundSignalIN = 7; // Ultrasound signal pin

unsigned long ultrasoundValue = 0;

void setup()


unsigned long ping(){
pinMode(ultraSoundSignal, OUTPUT); // Switch signalpin to output
digitalWrite(ultraSoundSignal, LOW); // Send low pulse
delayMicroseconds(2); // Wait for 2 microseconds
digitalWrite(ultraSoundSignal, HIGH); // Send high pulse
delayMicroseconds(15); // Wait for 15 microseconds
digitalWrite(ultraSoundSignal, LOW); // Holdoff
pinMode(ultraSoundSignalIN, INPUT); // Switch signalpin to input
digitalWrite(ultraSoundSignalIN, HIGH); // Turn on pullup resistor
// please note that pulseIn has a 1sec timeout, which may
// not be desirable. Depending on your sensor specs, you
// can likely bound the time like this — marcmerlin
// echo = pulseIn(ultraSoundSignal, HIGH, 38000)
echo = pulseIn(ultraSoundSignalIN, HIGH); //Listen for echo
ultrasoundValue = (echo / 58.138) * .39; //convert to CM then to inches
return ultrasoundValue;


void loop()
int x = 0;
x = ping();
delay(250); //delay 1/4 seconds.


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