0.7 Lab 4-2 putting it all together: an interrupt driven msp430

A more complicated assembly program

By now you already have all of the tools you need to complete this assignment. Remember what you have learned about MSP430 assembly language , setting up GPIO , and using interrupts .

1. Coding in MSP430 assembly, implement an interrupt driven number sequence recorder . You will use the same input configuration from last week (get data from pins 9.4-9.7 on an interrupt from pin 3.7), but now will output a readable loop of the last 5 received numbers in order. Assignment Details

Part ii assignment detail

Your task is to write an assembly program to display a programmable sequence of 5 numbers on the MSP430 ESCAPE Platform.

• You should use five slots to store the input numbers.
• Since our simple setup only has one display, you will have to rotate through each of the five numbers after a "short" (in human terms) delay.
• Use an ISR to store a new number in the "next" slot. (Next not necessarily meaning what is currently being displayed). The input should go from slot 1 to 2 to 3... etc. regardless of which slot is currently being output.
• The program should only display a slot after a number has been input into it. You will need to keep track of which slots have been filled.

• A setup routine that readies all the components of your program.
• A main loop that displays the stored numbers one after the other with a readable delay in between.
• An ISR that stores each new input number to the appropriate slot.

A few hints:

• The MSP430 operates at ~13MHz, which may seem slow in terms of computers, but is much too fast for the human eye to process (~30Hz). You will have to implement a very significant delay in between number changes.
• One way to generate a naive delay is a long loop which does nothing. You may even need to use a nested loop depending on how long of a delay you need.

  Nested Loop Example in C:

  int i=0; int j=0;for (i=0; i<bigNumber; i=i+1) {for(j=bigNumber; j>0; j=j-1) {<!--This code will run ixj times-->; }}
• You may find it convenient to put your five slots in RAM instead of using registers. You can then store a memory address in the register, and then increment it or set it as needed. You will need to use indirect addressing mode though. mov R4, 0(R15); moves the contents of R4 to the address in R15 mov 0(R15), R4; moves the contents of the address in R15 into R4 mov&0x006300, R4; moves the contents of memory address 0x006300 into R4
• Consider where it may be useful to implement parts of your program in subroutines

Wrapup

Congratulations on completing lab 4! Your program sophistication has dramatically increased. You understand the basics of interrupt driven programming , and know how to use assembly level subroutines . You have had to keep track of data as well as design a responsive I/O interface to the outside world. Keep up the good work!

Labs based on the original Elec 220 labs maintained by Michael Wu.

Images from original lab documents by Yang Sun. Modified by Matt Johnson.