Embedded Systems and Software

Size: px

Start display at page:

Download "Embedded Systems and Software"

Sabrina Newman
6 years ago
Views:

1 Embedded Systems and Software Lab 6 Considerations Lab 6 Considerations, Slide 1

2 Big Picture Connect to internal ADC V - Sensor To COM port on PC LCD RTC Optional: LCD display Lab 6 Considerations, Slide 2

Big Picture Many things will be + 0-5 V - Sensor connected to the controller.

3 Big Picture Many things will be V - Sensor connected to the controller. To COM port on PC Carefully assign pins LCD RTC Lab 6 Considerations, Slide 3

4 Serial Connection One must connect AVR to the RS232 Level Shifter and Drivers Lab 6 Considerations, Slide 4

5 Lab 6 Considerations, Slide 5

6 To COM port on PC Leave other pins and jumpers alone: we are NOT using flow control Lab 6 Considerations, Slide 6

7 Terminal Computer Serial Connection Terminal Lab 6 Considerations, Slide 7

8 SecureCRT Terminal Emulator Lab 6 Considerations, Slide 8

9 SecureCRT Terminal Emulator Select File Quick Connect Lab 6 Considerations, Slide 9

10 SecureCRT Terminal Emulator Quick Connect Menu Lab 6 Considerations, Slide 10

11 SecureCRT Terminal Emulator Select Serial Lab 6 Considerations, Slide 11

12 SecureCRT Terminal Emulator Serial Settings Menu Lab 6 Considerations, Slide 12

13 SecureCRT Terminal Emulator Enter your settings Lab 6 Considerations, Slide 13

14 SecureCRT Terminal Emulator This depends on the computer. Try COM1, or COM2 Lab 6 Considerations, Slide 14

15 SecureCRT Terminal Emulator Turn off all flow control Lab 6 Considerations, Slide 15

16 SecureCRT Terminal Emulator Set the rest of the parameters: 8N1 Lab 6 Considerations, Slide 16

$\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; sei();$ usart_init(); usart_prints(sdata); usart_printf(fdata); // Enable interrupts // Initialize the USART // Print a string from SRAM // Print a string from FLASH You have to

usart_init(); usart_prints(sdata); usart_printf(fdata); // Enable interrupts // Initialize the USART // Print a string from SRAM // Print a string from FLASH You have to

17 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; sei(); usart_init(); usart_prints(sdata); usart_printf(fdata); // Enable interrupts // Initialize the USART // Print a string from SRAM // Print a string from FLASH You have to implement these routines. Refer to previous lecture on serial communication. Also, there are many resources available on the internet: Peter Fluery, etc. You can user these, but need to understand how the software works. Lab 6 Considerations, Slide 17

$\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; You have to implement this routine, by$

18 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; You have to implement this routine, by calling lower level usart routines // Get the date, make a formatted string, and then // send via the USART. getdate(&yy,&mm,&dd); sprintf(str,"date: %d/%d/%d\n",yy,mm,dd); usart_prints(str); Lab 6 Considerations, Slide 18

19 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; You have to implement this routine, by calling lower level usart routines. // Get the date, make a formatted string, and then // send via the USART. getdate(&yy,&mm,&dd); sprintf(str,"date: %d/%d/%d\n",yy,mm,dd); usart_prints(str); Review the C standard library sprintf function. Lab 6 Considerations, Slide 19

20 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; You have to implement this routine, by calling lower level usart routines. // Get the date, make a formatted string, and then // send via the USART. getdate(&yy,&mm,&dd); sprintf(str,"date: %d/%d/%d\n",yy,mm,dd); usart_prints(str); Review the C standard library sprintf function. Make sure you include the proper headers file This will significantly increase the size of your code. Lab 6 Considerations, Slide 20

21 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; This is how to get the characters the user types at the PC keyboard into a character string. // Read in the year part of a date. usart_prints("please Enter Year (yyyy):"); for (i=0;i<=4-1;i++){ c = usart_getc(); // Get character usart_putc(c); // Echo it back str[i] = c; } str[i] = '\0'; Lab 6 Considerations, Slide 21

22 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; This is how to get the characters the user types at the PC keyboard into a character string. // Read in the year part of a date. usart_prints("please Enter Year (yyyy):"); for (i=0;i<=4-1;i++){ c = usart_getc(); // Get character usart_putc(c); // Echo it back str[i] = c; } str[i] = '\0'; This routine also echo s the typed characters back so the user can see what he/she is typing. Lab 6 Considerations, Slide 22

$\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String$ in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i;

$usart_prints("please Enter Year (yyyy):"); for (i=0;i<=4-1;i++){ c =$ $str[i] = '\0'; This routine also echo s the typed characters back so the user can$

23 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; This is how to get the characters the user types at the PC keyboard into a character string. // Read in the year part of a date. usart_prints("please Enter Year (yyyy):"); for (i=0;i<=4-1;i++){ c = usart_getc(); // Get character usart_putc(c); // Echo it back str[i] = c; } str[i] = '\0'; This routine also echo s the typed characters back so the user can see what he/she is typing. Use code such as this for your getdate routine. Lab 6 Considerations, Slide 23

24 String Conversion How does one convert from a string to a number? For example, consider the string str: const char str[] = "123"; We want to convert this to a number n = 123 so we can do arithmetic: n = str2num(str); n = n + 10; // Convert to number // Do arithmetic Where do I get a strnum routine? An easy method is to use the C compiler s string scan routine sscanf. (Next slide). Potential problem with this is that it pulls in large chunks of code which can quickly fill up flash memory. Lab 6 Considerations, Slide 24

$\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; Note how we used the sscanf routine to do$

25 const char sdata[] = "Hello World!\n"; // String in SRAM const char fdata[] PROGMEM = "Flash Gordon\n"; // String in Flash int main(void) { unsigned char c; char str[25]; int yy,mm,dd; int i; Note how we used the sscanf routine to do the conversion from string to a number. // Convert the string to a number. sscanf(str,"%d",&yy); if ( yy < 2010) { sprintf(str,"\ninvalid year: %d\n",yy); usart_prints(str); } } usart_prints("please Enter Month (mm):"); Lab 6 Considerations, Slide 25

26 ADC (Analog to Digital Converter) Lab 6 Considerations, Slide 26

27 Only one ADC Microcontroller PINs Multiplexer (MUX) connects one PIN at a time to ADC. Lab 6 Considerations, Slide 27

28 This is where the data goes. Remember we have an 8-bit data bus. However, the ADC gives a 10-bit conversion, so there are two registers involved: ADCH and ADCL Lab 6 Considerations, Slide 28

29 Conversion Modes Single Conversion Mode. As the name implies, application software instructs the ADC to start a conversion. Flags are used to indicate while the conversion is in progress and/or done. Auto Triggering. Various sources (see table below) can trigger a conversion automatically. This allows for background processing: Timer overflow can trigger ADC which makes conversion automatically. Lab 6 Considerations, Slide 29

30 Note the first conversion takes longer than rest. Lab 6 Considerations, Slide 30

31 ADC Reference ADCs need a reference voltage to compare the voltage they measure with. The ATmega88 s ADC reference voltage sources selection is controlled by the REFS1 and REFS2 bits in the ADMUX register Lab 6 Considerations, Slide 31

Since 2 10 = 1024, it means for a 0-V input the ADCH and ADCL pair will hold 0 and for

32 ADC Reference On the development board, the AVCC pin is connected to the power supply. Thus, if you set REFS1 REFS2 to 01, the power supply voltage will be the reference. Since 2 10 = 1024, it means for a 0-V input the ADCH and ADCL pair will hold 0 and for an input voltage Vcc, the ADCH and ADCL will hold = Lab 6 Considerations, Slide 32

33 ADC Reference While using the power supply as a reference for the ADC is convenient, it is problematic is some instances. The power supply regulator s output voltage many not be very precise. Loads on the main power supply cause fluctuations and this now changes the reference for the ADC. Lab 6 Considerations, Slide 33

34 Lab 6 Considerations, Slide 34

FINAL EXAM. last name first name

FINAL EXAM. last name first name 55:036 Embedded Systems and Systems Software Spring, 2011 FINAL EXAM last name first name Notes: This is an open-book, open-notes exam Be sure to write legibly and clearly mark your answers Show your work