Lab 3 - SPI - "I/O"

Given code

Supplemental Slides

Mega Prelab

A hard copy of this Mega Prelab is required to be turned in as well as pushed to Bitbucket. Answers should not be handwritten. The timing diagram may be NEATLY drawn by hand with the assistance of a straightedge on engineering paper.

Delay Subroutine

In lab3_given.asm, you have the header for a subroutine (line 579), but there is no code. Write a subroutine that will create a 160ms delay. Show your analysis that proves the delay is indeed very close to 160 ms. Note: the clock rate is set to 8 MHz (see the first two lines of initMSP).

ILI9341 LCD BoosterPack

Look at the schematic for the LCD BoosterPack. Complete the following table. The pin number (1 - 20) should be the pin number that signal connects to on the MSP 430, and the PX.X should be the pin and port it connects to (e.g. P1.0).

Name Pin # PX.X

What are the hex values that need to be combined with the below registers for these signals to be properly configured? State whether that hex value needs to be used with the bis or bic instruction with each register to achieve these ends. If the register is not affected for that signal, simply say N/A.


Configure the MSP430

Look at the initMSP subroutine in the lab3_given.asm file. There are four pins being intialized on port 1: SCLK, CS, MOSI, and DC. What is the pin number (1-20) associated with each of these signals? What function does each signal serve? For example, SCLK is the serial clock.

Name Pin # Function
SCLK serial clock

Below the pin configuration code are some lines of code from the lab3_given.asm file (lines 136 - 143) to properly configure the SPI subsystem. Use this code to answer the next two questions.

1:        bis.b    #UCSWRST, &UCB0CTL1
3:        bis     #UCSSEL_2, &UCB0CTL1
4:        bis     #BIT0, &UCB0BR0
5:        clr    &UCB0BR1
8:        bic    #UCSWRST, &UCB0CTL1

Fill in the chart below with the function that is enabled by the lines 6&7 of the above code. Your device-specific datasheet can help.

Pin name Function

Next, describe specifically what happens in each of the eight lines of code above. Line 1 and 3 have been done for you as an example.

Line 1: Setting the UCSWRST bit in the CTL1 register resets the subsystem into a known state until it is cleared.
Line 2:
Line 3: The UCSSEL_2 setting for the UCB0CTL1 register has been chosen, selecting the SMCLK (sub-main clock) as the bit rate source clock for when the MSP 430 is in master mode.
Line 4:
Line 5:
Line 6:
Line 7:
Line 8:

Communicate with the LCD

The following code (lines 297 - 338) sends one byte (either data or command) to the TM022HDH26 display using its 8-bit protocol.

;    Name: writeCommand
;    Inputs: command in r12
;    Outputs: none
;    Purpose: send a command to the LCD
;    Registers: r12 preserved
    push    r12
    bic     #LCD_CS_PIN, &P1OUT
    bic        #LCD_DC_PIN, &P1OUT
    mov.b     r12, &UCB0TXBUF

    bit        #UCBUSY, &UCB0STAT    ;while UCBxSTAT & UCBUSY
    jnz        pollC

    bis        #LCD_CS_PIN, &P1OUT
    pop        r12

;    Name: writeData
;    Inputs: data to be written in r12
;    Outputs: none
;    Purpose: send data to the LCD
;    Registers: r12 preserved
    push    r12
    bic     #LCD_CS_PIN, &P1OUT
    bis    #LCD_DC_PIN, &P1OUT
    mov.b     r12, &UCBxTXBUF

    bit    #UCBUSY, &UCBxSTAT    ;while UCBxSTAT & UCBUSY
    jnz    pollD

    bis    #LCD_CS_PIN, &P1OUT
    pop    r12

Use this code to draw two timing diagrams (one for each subroutine) of the expected behavior of LCD_CS_PIN, LCD_DC_PIN, LCD_SCLK_PIN, and UCBxTXBUF from the begining of these subroutines to the end. Make sure that you clearly show the relationship of the edges in the clk and data waveforms.

Draw a pixel

The following code (lines 552 - 576) draws a pixel of a predetermined color at the coordinate (R12, R13). However, four subroutines are called to execute this seemingly simple task. Explain the purpose of each of the four subroutine calls:

Subroutine Purpose
;    Name: drawPixel
;    Inputs: x in r12, y in r13, where (x, y) is the pixel coordinate
;    Outputs: none
;    Purpose: draws a pixel in a particular spot
;    Registers: r12, 13, 14, 15 preserved
    push    r12
    push    r13
    push    r14
    push    r15
    mov.b    r12, r14
    mov.b    r13, r15
    call    #setArea
    mov        #COLOR1, r12
    call    #splitColor
    call    #writeData
    mov        r13, r12
    call    #writeData
    pop        r15
    pop        r14
    pop        r13
    pop        r12

(This marks the end of the Mega Prelab.)

Logic Analyzer

The answers to the logic analyzer section will be posted to Bitbucket in the lab writeup.

Physical communication

Connect the LCD Booster Pack to your TI Launch Pad. Make sure that the buttons on the Booster Pack are aligned with the buttons on the MSP430. The pin numbers on the Boosterpack should match the pin numbers of the MSP430.
Create a project around the lab3_given.asm file. Be sure to include your Delay160ms subroutine.

After you insert your subroutine into the code, run the program and observe the output on the LCD every time you press the S1 button.

When S1 is detected as being pressed and released (lines 103 - 105), the drawLine subroutine is called. The MSP430 generates several packets of data that are sent to the LCD, causing a horizontal bar to be drawn. Find the three calls to writeCommand and eight calls to writeData that generate these packets. In addition, scan the nearby code to determine the parameters being passed into these subroutines.

Configure the logic analyzer to capture the waveform generated when the S1 button is pressed and released. Decode the data bits of each 8-bit waveform. Explain how the packet contents correspond to what was drawn on the display. Be specific with the relationship between the values sent and what and where the pixels are drawn. Is the packet of information being sent actual data or is it a command? The "Line" column refers to the line of code from which the call to write something to the LCD originated.

Packet Line Command/Data 8-bit packet Meaning of packet

Be sure to label your signals on the logic analyzer and include screenshots (which can be saved to your external hard drive, for eventual posting in your lab notebook) of each analyzed signal.


All functionality must be demonstrated live to an instructor. You do not need to include pictures or videos of functionality in your report.

Required functionality:

Create a block on the LCD that is 10x10 pixels.

A functionality:

Move the 10-pixel block one block (10 pixels) in the direction of the pressed button (up, down, left, right).

Bonus functionality:

Write your name or nickname of at least 5 characters to the screen on a solid background when the S1 button is pushed.

Grading - Lab 3

Printable Lab 3 Cutsheet




Item Grade Points Out of Date Due
Mega Prelab On-Time: -------------------------------------------------------------------- Late: 1Day ---- 2Days 20 BOC L16
Required Logic Analyzer On-Time: -------------------------------------------------------------------- Late: 1Day ---- 2Days ---- 3Days ---- 4+Days 40 COB L19
Required Functionality On-Time: -------------------------------------------------------------------- Late: 1Day ---- 2Days ---- 3Days ---- 4+Days 20 COB L19
A Functionality On-Time: -------------------------------------------------------------------- Late: 1Day ---- 2Days ---- 3Days ---- 4+Days 10 COB L19
Bonus Functionality On-Time: -------------------------------------------------------------------- Late: 1Day ---- 2Days ---- 3Days ---- 4+Days 5 COB L19
Lab Notebook On-Time: -------------------------------------------------------------------- Late: 1Day ---- 2Days ---- 3Days ---- 4+Days 10 COB L19
Total 100

Lab 3 Deliverables

Functionality (30 + 5 bonus pts) - Demonstrated NLT COB Lesson 19

Required (20 pts)

A Functionality (10 pts)

Bonus Functionality (5 pts)

Required Logic Analyzer (40 pts) b Due NLT TAPS Lesson 19

  1. (3 pts) Brief overview of what is going on in setArea (pictures help!)

  2. (5 pts) Overview screenshot from logic analyzer with 11 setArea packets you captured clearly identified

    1. Include all signal labels (SCLK, CS, DC, MOSI)

    2. Placing label at position when CS goes low is fine

  3. (20 pts) Table of 11 setArea packets captured

    1. Using hex to represent 8-bit packet values preferred
  4. (5 pts ea) Two packet screenshots from logic analyzer

    1. One command packet example and one data packet example

    2. Include all signal labels (SCLK, CS, DC, MOSI)

    3. Label the data with its value

  5. (2 pts) Brief analysis

    1. Why do the values (SC, EC, command bytes, etc) that you captured make sense?

Lab Notebook (10 pts) b Due NLT TAPS Lesson 19

  1. Title and Author

  2. Corrected Prelab

  3. Screenshot of measured 160ms (within 1 ms) delay from logic analyzer

    1. Include any necessary explanation. How does it compare to your calculated results? What is your actual clock frequency (not 8 MHz)?
  4. Logic Analyzer section b setArea capture and explanation (see above)