1. Microprocessor based Design for Biomedical Applications MBE 3 – MDBA III : The ATmega8 Basic Features (2)

2. Let‘s repeat some important topics of the last lecture: AVR memories SFRs – GFRs Bit Operations GPIO Ports Clock Sources Interrupt Handling

3. Today: Fix the IDE – Bug (update AVR-Studio) Repeat blink.c source Use the Simulator Look at avr-gcc, avr-objdump, make ISR – Interrupt Service Routines Timer Interrupt Example 16-Bit Timer, Modes UART – Configuration and Modes Start with Uart Example

4. Blink.c – sourcecode review #include #define Bit(x) (1<<x) void delay_ms(uint16_t ms) { uint16_t t; for (t=0;t<ms;t++) _delay_loop_2(1843); // 1843 * 4 clock cycles gives 7372 cycles: // (approx. 1 millisecond at 7,3728 MHz } int main( void ) { DDRD = Bit(5); // DataDirection Port D: Pin D5 = Output (Led) PORTD= Bit(5); // Switch on led and deactivate pullups on the inputs while (1) { PORTD ^= Bit(5); // toggle D5 delay_ms(500); // wait 500 milliseconds } return(0); } Macro definition, shift left operation Function definition, call by value (call by reference: pointer) SFRs for Port D configuration Bit manipulation Port D (XOR) Include device specific definitions (SFRs,..)

5. Using the AVRStudio - Simulator additional information to the Getting_Started.pdf

6. Flow Control Peripherals Peripheral Details CPU status AVRStudio Simulator Overview

7. AVRStudio Simulator Overview Breakpoint Watch Window

8. AVRStudio Simulator Overview Register and Memory Views Watch Window Disassembly Window

9. AVRStudio Simulator notes ● Select the Crystal / Oscillator frequency to get accurate time measurements in the Simulator ● beware of delay loops (they take long to simulate) ● use „run to cursor“ or breakpoints for getting into interrupt handlers ● on-chip debugging is useful, needs devices with JTAG interface or debugWire interface

10. Using the WinAVR-Toolchain from commandline

11. WinAVR-Toolchain – avr-gcc.exe Compile Link Convert.elf to.ihex Download to Device.elf: Executable and Linking Format, segment and section information

12. WinAVR-Toolchain – make.exe MAKEFILE The makefile automates the build process only changed modules are compiled Environment variables add flexibility current target current prerequistite Browse the GNU MAKE User Manual: http://www.gnu.org/software/make Rules Variables & constants Target SRC = blink.c test.c CFLAGS= -O2 -g -Wall PRG = $(SRC:.c=.hex) all: $(PRG) # Create.hex files from.o files %.hex : %.o echo Creating $@ avr-objcopy -O ihex $< $@ # Compile %.o : %.c echo Compiling $@ avr-gcc $(CFLAGS) -mmcu=atmega8 $< -o $@ clean: rm -f *~ *.bak *.lst *.o *.hexc

13. WinAVR-Toolchain – avr-objdump.exe Avr-objdump: Extract information from.elf – file Here: show disassembly information

14. Where to find AVR C - specific information ? ● AVR-GCC is ANSI-C compatible ● browse the AVR Libc – Documentation ● examine module header files (#include ) subdirectory avr/include ● use example code, play with open source firmware

15. Where to find AVR C - specific information ? : Diagnostics : Character Operations : System Errors : Integer Type conversions : Mathematics : Standard Integer Types : Standard IO facilities : General utilities : Strings, memory functions : Bootloader Support Utilities : EEPROM handling : Interrupts : Program Space Utilities : Power Reduction Management : Special function registers and IO definitions : Power Management and Sleep Modes : Basic busy-wait delay loops : Parity bit generation : TWI bit mask definitions Useful modules, all documented in the AVR-Libc manual !

16. Where to find AVR C - specific information ? typedef signed char int8_t typedef unsigned char uint8_t typedef signed int int16_t typedef unsigned int uint16_t typedef signed long int int32_t typedef unsigned long int uint32_t typedef signed long long int int64_t typedef unsigned long long int uint64_t #define INT8_MAX 0x7f #define INT8_MIN (-INT8_MAX - 1) … Standard integer and character types, defined in : 8, 16, 32 and 64 bit, signed and unsigned Constants for min and max values

17. Where to find AVR C - specific information ? void memcpy (void, const void, size_t) void memmove (void, const void, size_t) char strcat (char, const char ) char strstr (const char, const char ) char strupr (char ) … Some functions from :

18. Interrupt handling with the AVR-Libc API Interrupt and Signal definitions: ● remember: vector table points to interrupt routines ● by using the appropriate name, your routine will be installed in the table and called when the interrupt occurs ● a set of default interrupt routines is provided ● Macro for registering interrupt routines: ISR ( ) ● saving and restoring registers is handled

19. Interrupt handling with the AVR-Libc API Examle interrupt handler for the ADC: #include ISR(ADC_vect) { // user code here } ● The interrupt source, here the ADC, has to be configured and enabled using SFRs ● Global interrupt instructions: sei () … set interupt enable (I – bit in SREG) cli () … clear interrupt enable ● AVR hardware clears the global interrupt flag before entering an interrupt vector -> use sei() to enable nested interrupts

20. Interrupt handling with the AVR-Libc API Useful Interrupt vector names for ATmega8: ADC_vect analog/digital converter ANA_COMP_vect analog comparator EE_RDY_vect eeprom ready INT0_vect external interrupt 0 TIMER0_OVF_vect Timer0 overflow event TIMER1_CAPT_vect Timer1 capture event SPI_STC_vect serial transfer complete USART_UDRE_vect USART data register empty USART_RXC_vect USART receive complete

21. more AVR Peripheral Features

22. 16 – bit Timer / Counter 1 ● Two Independent Output Compare Units ● can be used as Pulse Width Modulator (PWM) ● Clear Timer on Compare Match (Auto Reload) ● One Input Capture Unit ● can be used as External Event Counter ● Four Independent Interrupt Sources TOV1, OCF1A, OCF1B, and ICF1

23. 16 – bit Timer / Counter 1 ● TCNT1, OCR1A, OCR1B and ICR1 are 16-bit registers ● write high byte first read low byte first (automatically done in C) ● clocking via prescaler or external clock on pin T1 ● output compare register OCR1A/B can be used for PWM generation (output pin: OC1A/B) or for interrupt request

24. 16 – bit Timer / Counter 1 ● Input capture Unit: timestamp external events on ICP1 pin (or on Analog comp.) Can generate Input Capture Interrupt

25. 16 – bit Timer / Counter 1 ● Output Compare Units: compare TCNT1 with OCR1A and OCR1B Can generate Output Capture Interrupt ● 13 PWM / Waveform generation modes ● Top and Bottom values ● Auto reload

26. 16 – bit Timer / Counter 1 ● Mode configuration using TCCR1A and TCCR1B PWM Mode, set/clear/toggle of OC1A/B, auto-reload, Noise canceller Find Details in the ATmega8 datasheet !

27. 16 – bit Timer / Counter 1 ● Clock source configuration using TCCR1B

28. The UART Serial Interface

29. USART interface ● universal synchronous / asynchronous receiver / transmitter ● Full Duplex Operation: Receive and Transmit Registers ● Asynchronous or Synchronous Operation ● Frames with 5, 6, 7, 8, or 9 Databits and 1 or 2 Stop Bits ● Odd or Even Parity Generation and Parity Check ● Framing Error Detection, Noise Filtering ● Interrupts possible on TX Complete, TX Data Register Empty and RX Complete

30. USART interface ● synchronous mode: Pin XCK is used as clock Input (slave) or clock output (master) ● asynchronous mode: receiver and transmitter are clocked independently

31. USART interface ● Frame formats:

32. USART interface ● calculating the baud rate register value: low and high byte of ubrr are written into the UBRRL and UBRRH registers Accuracy depends on System clock source ! (see table in ATmega8 data sheet, pp 155)

33. USART interface ● Initialisation: set baud rate, frame format, enable TX and RX RXC: RX complete TXC: TX complete UDR: Uart Data Register empty FE: Frame Error DOR: Data OverRun PE: Parity Error U2X: Double the USART speed

34. USART interface ● Initialisation: set baud rate, frame format, enable TX and RX RXCIE: RX complete interrupt enable TXCIE: TX complete interrupt enable UDRIE: Uart Data Register empty interrupt enable RXEN: Receiver Enable TXEN: Transmitter Enable UCSZ2: Character Size RXB8, TXB8: Bit 8 for receive and transmit

35. USART interface ● Initialisation: set baud rate, frame format, enable TX and RX URSEL: Register Select (1=UCSR/0=UBRRH) UMSEL: 0=async. mode, 1=sync. Mode UMP1, UMP0: Parity mode: 00 = disabled, 10 = even, 11=odd USBS: Stop Bits: 0=1 Stop Bit, 1= 2 Stop bits UCSZ2,1, 0 : character size

36. USART interface character size selection using the UCSZ bits

37. USART interface Selection of the baud rate using the UBRRH and UBRRL SFRs: URSEL has to be 0 when writing to the UBRRH register

38. USART interface ● Initialisation: set baud rate, frame format, enable TX and RX void USART_Init( unsigned int baud ) { /* Set baud rate */ UBRRH = (unsigned char)(baud>>8); UBRRL = (unsigned char)baud; /* Set frame format: 8data, 2stop bit */ UCSRC = (1<<URSEL)|(1<<USBS)|(3<<UCSZ0); /* Enable Receiver and Transmitter */ UCSRB = (1<<RXEN)|(1<<TXEN); }

39. USART interface ● Sending bytes in polling mode void USART_Transmit( unsigned char data ) { /* Wait for empty transmit buffer */ while ( !( UCSRA & (1<<UDRE)) ); /* Put data into buffer, sends the data */ UDR = data; }

40. USART interface ● Receiving bytes in polling mode unsigned char USART_Receive( void ) { /* Wait for data to be received */ while ( !(UCSRA & (1<<RXC)) ) ; /* Get and return received data from buffer */ return UDR; }