RTC example on ARM7 LPC2148 using WinARM

Finally got my LPC2148 RTC working on my development board. arm7 base development board for lpc2148 I am quite new to ARM microcontrollers, so I managed to make few tests using them by driving some peripherals and writing some test routines. First code I tried was simple LED blink program first lpc2148 arm7 microcontroller test led blink This one is running microcontrollers real time clock (RTC) and generating interrupts every second. When Interrupt occurs microcontroller sends particular message to UART that I could see via Terminal program. The main program: /****************************************************************************** * * WinARM RTC application * * – UART0 send in Interrupt-Mode * – Sends message every seccond. * – RTC interupt every second ******************************************************************************/ #include “types.h” #include “LPC214x.h” #include “config.h” #include “armVIC.h” #include “uart.h” uint32_t time_toggle=0; static void rtc0(void) __attribute__ ((interrupt (“IRQ”))); static void lowInit(void) { // set PLL multiplier & divisor. // values computed from config.h PLLCFG = PLLCFG_MSEL | PLLCFG_PSEL; // enable PLL PLLCON = PLLCON_PLLE; PLLFEED = 0xAA; // Make it happen. These two updates PLLFEED = 0x55; // MUST occur in sequence. // setup the parallel port pin IO0CLR = PIO0_ZERO_BITS; // clear the ZEROs output IO0SET = PIO0_ONE_BITS; // set the ONEs output…

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Microcontroller eats too much of RAM

All you know that microcontrollers have limited amount RAM and EEPROM. For instance ATMega128 has 4-Kbytes of RAM, 4-Kbyte of EEPROM. This may seem quite enough for some applications, but more complicated routines require more of RAM. And there is no compiler that can do better optimization on usage of ram than programmer. The main aim of reaching this is reducing dependence on global data, stack and the heap. So if your application running in microcontroller eats too much of RAM then you should develop some strategy of using its RAM. Lets see… if you use constants as global values, why not to move them to EEPROM area? You can easily do this by compiler when you declare your variables by using const keyword: const uint8_t a=10; I compiled some code using this declaration and compiler (AVR-GCC) compiled .eep file which can be burned to microcontrollers EEPROM. In this way you can store your constants to your EEPROM memory. Another factor eating microcontroller RAM is stacks. Try to use us much stack as your program require and leave some reserved space just in case. There are many techniques that can help define requirement of stack memory. One of them is…

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Minimizing microcontroller code size

Reducing microcontroller code size isn’t ease task, but what if you want resulting code to fit your available memory? Minimizing microcontroller code size can be done in two ways: Firs is using compilers optimization feature by code size. This optimization is very dangerous. Your optimized code may not work as supposed to because compiler may eliminate some code like empty loops or adding zeros. For example compilers like to remove for(int i=0;i by leaving one or several iterations. So don’t think that your optimized code will work as un-optimized. There are other things you can do to minimize microcontroller code size. One of them is avoiding usage of standard libraries routines. Because these libraries are general and handles all standard possible execution cases. By including them in your design you include a bunch of code you dont need. If it is possible it is better to write your own routines or modify existing ones to fit your needs. Also try to use needed variable sizes. If you need unsigned integers use uint type if you need byte size avoid using int which usually is more than 8 bits (16 or 32). This may significantly reduce your code as there are fewer…

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Increase microcontroller code efficiency

C compilers are getting more and more advanced, but there is always a trade off made between speed and code size. Compiled code can be faster or smaller but not both. So you have to choose which part is more important speed or code size. The Increase of microcontroller code efficiency can be done in many ways. Don’t trust compiler optimization features, as they might not bee as effective as you expect. It is better to grab some profiler and inspect what parts of your code takes the most time and size. It is better to follow some techniques that may reduce code execution time and increase microcontroller code efficiency:

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Interfacing LCD to Atmega using two wires

This is not new Idea of interfacing LCD using two wires, but it can help in many situations when there is not enough of microcontroller pins. This example is based on Hitachi 44780 Alphanumerical LCD. This circuit I provide is only to represent an idea but I think it should work also if soldered. We know, that to make LCD working you need at least 6 (in 4 bit mode) wires to control. But what if you need as many pins as possible from your avr and still want to see results on LCD. Then you need to use serial LCD or make one. In this example you just need to convert serial data coming to LCD using shift register. I suggest using 74HC164. You need only two wires to push data to shift register and then give them to LCD using “E” strobe signal. So how this operates? Atmega’s PC1 pin clocks shift register and PC0 is data line. Before you write to shift register clean it by sending “0” in eight clock cycles. You can erase register with additional wire controlling register reset, but there would be 3 lines used. After register is cleared, send eight bits to…

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Power sources for AVR

Power sources for AVR are very important part in projects. Avery circuit has to be powered from some source like battery or from AC adapter 110V/220V. Using batteries is more convenient way to power the microcontroller projects as the circuits are simpler and constructed devices become portable. There are many types of batteries in shapes and sizes or capacities. So when choosing battery you should consider many factors: Capacity – this is very important parameter measured in mA/h. This parameter defines how long your microcontroller project will be working before recharging or replacing batteries. Rule is simple – as bigger battery capacity as longer your circuit will be working, but in other hand your project may become more expensive or even heavier because of bigger batteries. Second parameter is battery Voltage. If Voltage of battery is to small for tou circuit, youll have to connect several batteries in series. Other is Expirity date. You don’t want your battery energy leakage or become obsolete because of this. Working temperature. If your project will be working in more extreme temperatures – heat or cold, then you should consider this. And the last parameter would be chape, size and weight. If your project…

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Atmega EEPROM memory writing

All atmega family microcontrollers have internal EEPROM memory. They can have from 512bytes to 4kBytes. EEPROM memory has its own memory space and is linearly organized. In order to access EEPROM mempry in atmega there are three registers used: Address register, Data register and Control register. Address register EEAR (EEPROM Address Register) is made of two 8 bit registers EEARH:EEARL. In this register the EEPROM cell address has to be loaded. Data register EEDR (EEPROM Data Register). When writing to EEPROM the data is loaded to this register. When getting data from EEPROM – you read data from this register. Control register EECR (EEPROM Control Register) is used to control access to EEPROM memory. EERIE – EEPROM Ready Interrupt Enable. This bit generates interrupt after write cycle is finished. If bit is set to ‘1’ and also I bit SREG, then EEPROM Ready interrupt is enabled. If bit is set to ‘0’ – then interrupt is disabled. EEMWE – EEPROM Master Write Enable. The EEMWE bit determines whether setting EEWE to one cause the EEPROM to be written. When EEMWE is set, setting EEWE within four clock cycles will write data to the EEPROM at the selected address If EEMWE…

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