EENG 383

• Convert serial stream
  [Serial] → Mode → UART/RS232
  [Serial] → Serial → Serial 1: UART/RS232 ✓
  [Serial] → Signals → Rx → 1
  [Serial] → Signals → Threshold → (Trigger Level) → 1.65V
  [Serial] → Bus Config → #Bits → 8
  [Serial] → Bus Config → Parity → None
  [Serial] → Bus Config → Baud Rate → Baud → 9600 b/s
  [Serial] → Bus Config → Polarity → Idle high
  [Serial] → Bus Config → Bit Order → LSB
  [Serial] → settings → Base → ASCII
  
• Clear all menus off the bottom of the screen
  [↑Back]
• Screen shot the screen on USB:
  [Save] → Save → Format → 24-bit Bit... (*.bmp) [Save] → Save → Press to Save

1. Screen capture the '5' character on your oscilloscope and include it in your report. Make sure to show the serial decoding at the bottom of the screen.
2. Complete the following table for the character listed in the left most column. Remember that every transmitted character has a start and stop bit (do not include) and is transmitted LSB first.
   • Fill in the "Bit period" column with the shortest bit period (in microseconds) duration for that character. To determine the bit period, find, and measure, the shortest logic "1" or logic "0" pulse. You can measure the duration of the pulse using the horizontal scale or by using the Cursor function activated by pressing the cursor button.
   • Fill in the "Bit frequency" column with the reciprocal of the Bit period. Use units of bps (bits per seconds) instead of Hertz (cycles per second).
   • Extract the 8-bit binary code from the data sent, making sure to ignore start and stop bits and ordering them from MSB (left) to LSB (right) and put it into the "Binary code for data" column,
   • Convert the 8-bit binary code data into 2 hex characters and put the value in the "Hex code for data" column,
   • Use an external resource to look-up the ASCII character for each of the Hex codes and put it into the "ASCII char for data" column.

   Character sent	Bit period (us)	Bit frequency (bps)	Binary code for data	Hex code for data	ASCII char for data bits
   'a'
   'A'
   <Enter>
   <Backspace>

Internal Subsystem

3. Using Table 2 on page 6 of the Data Sheet (for the 28-pin SSOP package), what I/O pins are associated with the EUSART1? Note, we are not using the EUSART2 subsystem nor its associated pins.
4. The baud rate generator inside the PIC slows down the main oscillator by dividing it by the value stored in the baud rate generator register pair SPBRGH1:SPBRG1 to make the 9600 baud rate clock used to produce bits. Note the ":" symbol separating the two register names means that we are building a 16-bit value with SPBRGH1 as the upper 8-bits and SPBRG1 as the lower bits. The relationship between the main oscillator frequency (Fosc) and the baud rate is given in Baud Rate Formula column of Table 16-3 in the Microchips PIC18(L)F2X/4XK22 Data Sheet. The value n in the equation (per the legend) is the SPBRGH1:SPBRG1 register pair and the answer to this question.
   The bit sequence observed in the previous section was asynchronous (SYNC = 0) because it was not accompanied by a clock. We will be using the high speed 16-bit baud rate generator (BRG16 = 1 and BRGH=1).
   Determine the value for the 16-bit baud rate generator SPBRGH1:SPBRG1 to generate a 9600 baud rate assuming that the PIC is running at 64MHz. Show your work and state your 16-bit answer in hexadecimal.
5. Look at the Figures 16-1 and 16-2, what register would you write to in order to transmit (TX) a data byte out of the PIC? What register would you read in order to receive (RX) a data byte sent into the PIC? Note that these registers need to be connected to the data bus.
6. Look at the Figures 16-1 and 16-2, what flag indicates when a data byte can be transmitted out of the PIC? What flag indicates that a data byte has been received by the PIC? Note that these flags are connected to the TX and RX register.
7. Read about the TX1IF and RC1IF flag in the PIR1 register defined on page 112. How are each of these flags cleared?

Firmware Organization

• Launch MPLab X
• Close any open project: File → Close All Projects
• Create a new inLab05 project as you did in Lab 4. Make sure, at step 2 (Select Device), to choose PICKit 3.
• Click Tools → Embedded → MPLab Code Configurator
• If the MPLab Code Configurator is not listed then you will need to install the Code Configurator as follows:
  • Tools → Plugins,
  • In the Plugins pop-up select the "Available Plugins" tab,
  • Check the "MPLab® Code Configurator" check box,
  • Click Install,
  • In the Plugin Installer pop-up, click Next,
  • Accept the terms, click Install,
  • Check the "Restart Now" radio button, click Finish,
  • Wait for netBeans Platform to do its thing and then proceed,
  • When MPLab launches, open the MPLab Code Configurator.
• In the Save MCC Configuration File pop-up, keep defaults and click Save,
• In the INTERNAL OSCILLATOR area of the System Module window
  • Oscillator Select: Internal oscillator block
  • System Clock Select: FOSC
  • Internal Clock: 16MHz_HFINTOSC
  • Software PLL Enabled: Check
  The Current System clock should be 64MHz (4x PLL)
• In the Device Resources area of the project window, expand the Timer option. Double click TMR0.
• In the Device Resources area of the project window, expand the EUSART option. Double click EUSART1 [PIC10/PIC12/PIC16/PIC18 MCUs by Microchip Technology Inc.]
• In the Device Resources area of the project window, expand the ECCP option. Double click ECCP1
• In the Device Resources area of the project window, expand the Timer option. Double click TMR2.
• In the Project Resources area of the project window, expand the Peripherals option if not already expanded, and click on TMR0.
  • Enable Timer: ✓
  • Enable Prescaler: ✓
  • Prescaler: 1:16
  • Timer mode: 16-bit
  • Clock Source: FOSC/4
• In the Project Resources area of the project window click on EUSART1. Note □ means to leave the box unchecked. A ✓ means to check the associated box.
  • Enable EUSART: ✓
  • Enable Transmit: ✓
  • Enable Wake-up: □
  • Auto-Baud Detection: □
  • Enable Address Detect: □
  • Baud Rate: 9600
  • Transmission Bits: 8-bit
  • Reception Bits: 8-bit
  • Clock Polarity: async_noninverted_sync_fallingedge
  • Enable Receive: ✓
  • Enable EUSART Interrupts: □
  • Redirect STDIO to USART ✓
• In the Project Resources area of the project window click on TMR2.
  • Enable Timer: ✓
  • Postscaler: 1:1
  • Prescaler: 1:16
  • Timer Period: 64 us
• In the Project Resources area of the project window click on ECCP1.
  • ECCP mode: Enhanced PWM
  • Timer Select: Timer2
  • PWM Duty Cycle: 50%
  • Enhanced PWM mode: single
  • PWM pins polarity: P1A,P1C: active high; P1B, P1D active high
  • Auto shutdown on: disabled
  • PWM Delay counts: 0x0
  In a future question you will need the information listed in the PWM parameters. Save yourself a little time and write down the values for PWM period, PWM Resolution, and PWM Frequency. Note that while the PWM resolution only requires 8-bits, you must use a 16-bit integer to hold the value because there are options which allow the PWM resolution to be greater than 8-bits.
• File → Save All…
• Click on the "Generate" button in the Project Resources area of the project manager window. You should note activity in the Output area of the console showing that the code configurator is creating files associated with your project. Anytime that you make a change to the configuration you must re-generate the supporting files by clicking on the generate button,
• Double click the file main.c to open it in the editor window.
• Replace the contents of main.c with inlab05.c,
• Compile and download the code to the PIC,
• Launch PuTTY and connect to the serial port associated with the FT230 chip,
• Type "?" in the terminal. You should see,

  ------------------------------
  ?: Help menu
  o: k
  Z: Reset processor
  z: Clear the terminal
  t: Display current TMR2
  T: Display current TMR0
  p/P: decrease/increase duty cycle
  ------------------------------
  

• Connect a jumper wire between RC2 and an LED and experiment with the duty cycle,
• Experiment with the commands - see discussion below.

8. Each function prototype has a comprehensive block of comments that precede each function prototype. Look through the "@Summary" comments and identify the function that "Loads 16-bit duty cycle." List the associated function prototype.
9. What register and field are used for the EUSART1_DataReady? Note, this is in one of the #defines in eusart1.h.
10. When writing a value to TMR0 using the TMR0_WriteTimer function, what data-type should the input argument be?
11. Look through the comments in front of the TMR0_HasOverflowOccured function prototype in tmr0.h. In the example code section, how is the TMR0 interupt flag cleared?

12. In the EUSART1_Initialization function (found in MCC Generated File → eusart1.c), what 16-bit value (in hex) is written to the baud rate generator registers SPBRGH1:SPBRG1? Compare this value to an earlier answer.
13. What PIC data registers does the EUSART1_Read function get the incoming character from? Hint, it is the returned value. What PIC data registers does the EUSART1_Write function put the outgoing character to?
14. When performing a read what flag does the EUSART1_Read function wait on?
15. When performing a write, what flag does the EUSART1_Write function wait on? If the EUSART1_Write must wait on this bit, what does it imply about the the status of the EUSART transmitting hardware?

16. List the invocation(s) of #defines contained in the MCC Generated Header Files that are present in the main.c file.
17. List all calls to functions contained in the MCC Generated Source Files that are present in the main.c file.

18. Is there a format character to print a value in binary? If so what is it? Is there a format character to print a value in octal? If so what is it? Is there a format character to print a value in hexadecimal? If so what is it? What is the difference between using an upper or lower case "x" when printing values?
19. For the RESET function on page 400, what library do you need to include in order to access this function? What MCC Generate header files (there are more than one), found in your project, contains the #include to this library?

Firmware Experiments

20. Complete the table using the output shown in the terminal.

    format	'0'	0x30	0xAB	0xABCD	0xABCD0123
    %c			unprintable
    %u		48
    %d					291
    %x	30
    %04x				abcd
    decimal			171

21. As you discovered in the previous problem, printing out 32-bit values is problematic. Problematic in the sense that it cannot be done. If you need to print a 32-bit value you must print it as a pair of 16-bit values, the upper 16-bits and then the lower 16-bits. To do this you will need to use a shift operation to move the upper 16-bits (of the 32-bit variable) into the lower 16-bits. Then you will need to mask off the lower 16-bits (of the 32-bit variable).

    	uint32_t var32 = 0xABCD0123;	
    	// print var32>>16 in a single printf statement
    	// print var32&0xFFFF in a single printf statement
    

    Write a pair of printf statements that prints 8 hexadecimal characters of a 32-bit variable with "0x" in front of the 8 hexadecimal characters. You need to print leading zero's in each 4 hex character output using the "04" format specifier. Obviously, it would be a good idea to try out your idea in code.
    
    I have not been able to get the following to work on our compiler. Having this capability would really simplify printing 32-bit integers. If you put #include <inttypes.h> at the top of your program (just below mcc_generated_file/mcc.h) then you can use the following to print 32-bit variables.

    printf("0x%08" PRIx32 "\r\n",var32);
    

22. Connect an oscilloscope to RC2 and determine the PWM resolution. The PWM resolution is the time (in us) per duty cycle count. To do this:
    • Measure the time high of the PWM waveform,
    • Note this initial duty cycle value,
    • Change the duty cycle value, noting the new value,
    • Measure the time high of the PWM waveform,
    • Compute the difference of the times high,
    • Compute the difference between the duty cycle values,
    • Compute the ratio difference in times high over difference in duty cycle values.