Microcontroller

by Dost Muhammad Shah on Electronics, Microcontrollers

STM32 Microcontrollers – Prior to Start

STM32 ARM-based micros from STMicroelectronics pack high density resources than any other conventional microcontroller. They are also high speed devices, operating typically at 72MHz and beyond. Despite several advanced features and heavy resources, they turn out to be misfortunes for beginners who wish to play with them. Available in market are several cool STM32 boards but most of them are not well documented. The aim of this document is to address some common FAQs.

Typically most people ask the following question:

  • How to program the STM32 micro embedded in my development board?
  • What tools do I need to get started?
  • What compiler support do I have for STM32?
  • What resources are available for STM32 on the internet?

… →

 
by Dost Muhammad Shah on Electronics, Microcontrollers

writing and reading from AVR EEPROM in Block.

EEPROM can be used to store non volatile data of the program , sometimes you need to write arrays even multidimensional. The way I do it is by using EEMEM attribute. EMMEM is used to allocate space in EEPROM.

I use the Macros given below to write or read to EEPROM. you have to use #include I would be precise . below is the Code.

#include

//////////////////////////////////////////////////////////////////////////
//        Macros and # Defines
//write block to EEPROM
#define eepw(message,EEADDR,BLKSIZE) eeprom_write_block((const void*)message,(void*)EEADDR,BLKSIZE);
//read block from EEPROM
#define eepr(readblck,EEADDR,BLKSIZE) eeprom_read_block((void*)readblck,(const void*)EEADDR,BLKSIZE);

uint8_t EEMEM eepstring[15];

Example use

eepw("sample test 1",eestring, 15);  // "writes sample test1" to eestring in EEprom ,
char d[15];   //array in ram
eeprom_read(d, eestring[0],15); // reads the data and puts it in d[]

 
by Dost Muhammad Shah on Coding, Electronics, Microcontrollers

Keeping track of time in embedded applications: millis();

Its very handy to keep track of time in embedded programs. In this post I will implement a function called millis() which can be used to track time.  Arduino users will be familiar with this one. I would be doing it for AVR MCUs you can easily port it for others. this function returns the number of milliseconds since the MCU began running the current program. This number will overflow (go back to zero), after approximately 50 days.
It uses a hardware timer , in this post i will use timer0 . The first step is to initialize timer0 and interupts. lets start.

void timer0(){
  // To set clock:
  // 1MHZ is 1,000,000 ticks per second
  // 1000 milli in 1 second
  // xMHZ = 1000millis
  // so MHZ/millis gives # HZ per millis
  // (HZ/millis)/prescaler= Top counter number

  // EG:for 8MHZ clock
  // 8000000/1000
  // 8000.0000000000
  // 8000/256
  // 31.2500000000 TOP counter

  //set CTC (clear timer on compare match mode)
  TCCR0A = (1< <WGM01);
  //sets prescaler clkIO/256  ***THIS MIGHT CAUSE ISSUES SETS FOR ALL CLOCKS**!!!!
  TCCR0B = (1<<CS02);
  //sets interrupt enable for OCF0A (TIMER_COMPA_vect)
  TIMSK0 = (1<<OCIE0A);
  //sets TOP counter match A at 31
  OCR0A = 31;
}


volatile uint32_t millis()
{
 uint32_t mill;
 uint8_t oldSREG = SREG;
 // remember last value of interrupts
 // disable interrupts while we read timer0_millis or we might get an
 // inconsistent value (e.g. in the middle of a write to timer0_millis)
 cli();
 mill = millis_count;
 SREG = oldSREG; // rewrite reg value to turn back on interrupts
 return mill;
}

In the code shown above we have initialized timer/counter 0 to make an interrupt after every millisecond. Next we have to update our millisecond count.

//interrupt declaration
ISR(TIMER0_COMPA_vect)
{
  ++millis_count;
  //OCR0A = 10; //sets upper breakpoint A
}

That’s it. Lets see how to use it! First we copy the current value in milis() to a variable.

uint32_t starttime=millis();

and later we compare the new values with the start value. Here’s an example of a 25 second.

if(millis()-starttime > 25000)
{
  // some code here
}

Note that the parameter for millis() is an unsigned long, errors may be generated if a programmer tries to do math with other datatypes such as ints.

There are a number of ways you can use this. Hope this post will help you

 
by Dost Muhammad Shah on Coding, Electronics, Microcontrollers

Disable CLK Pre-scaler in AVR to use 8MHz Internal Oscilator

Just wanted to share this small piece of information that can help many . If you want to Run your AVR at 8MHz from the internal oscillator you need to disable the CLK/8 Fuse. You can do this by burning new fuse values. This can also be done in you main function as well. Below is a piece of code that will change the pre-scaler to zero.

// set the clock speed to "no pre-scaler" (8MHz with internal osc or
// full external speed)
// set the clock prescaler. First write CLKPCE to enable setting of clock the
// next four instructions.
CLKPR=(1< 

Hope this will help!
	    		
 
by Dost Muhammad Shah on Electronics, Microcontrollers

Add Voice /Audio to projects using WTV020SD

Adding sound to your projects is great, there can be several methods to do it. In this post i will show how we can use wtv020-sd module to get this task done. I wont go in detailed description of the module and will keep the post short and to the point. The module can be operated in a number of modes including pushbutton modes but the one we are going for is the 3 wire serial mode. its actually SDA,SCL and reset wires that we use. The module would play back the ad4 files stored on uSD Card. and spk+ and spk- pins can be connected directly to a speaker. More details about the module can be found in the datasheet and the webpage link.

The interface is simple. you only need to connect Supply , DI ,CLK and reset Pins to get it working although you may also connect some other pins also but this is what is really needed to get the module working.

connections … →