Description
ARM Programming Refresher and CPLD Intro
Introduction
In this lab you will accomplish several goals:
• Develop an embedded application using IAR Embedded Workbench
• Write a C program to display a counter on the LCD of the STM32L-Discovery board (ARM board)
• Write an ARM assembly program to blink the LEDs of the STM32L-Discovery board (ARM board)
• Develop a PLD application using Lattice Diamond
• Solder header pins to your MachXO Breakout board (CPLD board)
• Write a Verilog program to count in Gray code on your MachXO Breakout board (CPLD board)
All lab assignments must be done individually.
Requirements
ARM Board
You have two main objectives involving your ARM board. First, you need to produce a counter on the LCD
of your ARM board using C. Second, you need to blink the LEDs on your ARM board using only assembly
language instructions. See later sections on how to mix C and assembly.
Your counter value must be present on the LCD and update at reasonable period (0.5 Hz–1 Hz). You
may select the counter base (e.g., decimal, hex, octal). The LCD should clear between values so only one
number appears on the LCD at any point in time. You may use any of the libraries present in the empty
project on Learn. In particular, look at the file stm32l_discovery_lcd.h in the empty project and the
demo program that you can download from ST’s website (look for the STM32L-Discovery firmware). If you
use code from another source, you must state that in your comments.
Your LEDs must update at the same frequency as the counter. You may select how to toggle the LEDs
(on/off pattern) as long as at least one LED changes per counter update. All operations on the LEDs,
including clock setup, port configuration, and value changes, must be done in ARM assembly.
Since the LEDs and counter are synchronized, it is recommended that you use a single loop to toggle the
LEDs and update the counter value. An empty for loop can provide the delay needed between counter and
LED updates.
CPLD Board
Your objective for the CPLD board is to create a counter using Gray code and display the value on the
LEDs present on the CPLD board. The counter must be at least 4 bits wide, but you may create a larger
counter if you desire. Your counter must be implemented in Verilog.
Additionally, you must solder at least a quarter of the header pins to your CPLD board by the demonstration day. If you need help soldering, be sure to attend the Solder Workshop on Feb. 22 at 1 PM in
OCNL 346.
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EECE 344 Lab 1
Mixing C and ARM Assembly
Throughout the semester, including this lab, you will need to create projects that include both C and
assembly code. This section will detail two ways to do this.
Assembly Function Called by C Program
In this setup you declare and call a function in C and then define the operation of the function in a separate
assembly file. The templates below show you how to setup your files to define two C functions, assembly1 and
assembly2, that take no arguments and produce no output and whose implementation is done in assembly.
Change these functions to suit your needs.
The C file would include:
extern void assembly1(void); /* Declare assembly1 */
extern void assembly2(void); /* Declare assembly2 */
int main(void){
/* … */
assembly1(); /* Call assembly1 */
/* … */
assembly2(); /* Call assembly2 */
/* … */
return 0;
}
The assembly file (including some constant definition examples) would include:
SIX_HEX EQU 0x06 ; Create a constant named SIX_HEX
THIRTYTWO_HEX EQU 0x20 ; Create a constant named THIRTYTWO_HEX
PUBLIC assembly1 ; Declare assembly1 as a public label
PUBLIC assembly2 ; Declare assembly2 as a public label
SECTION .text : CODE (2) ; Place the following code in the .text section
assembly1:
; Your code for assembly1 goes here
BX LR ; Return to calling function
assembly2:
; Your code for assembly2 goes here
BX LR ; Return to calling function
END ; End of assembly file
Inline Assembly
The alternative approach is to use inline assembly, where you insert assembly instructions directly into a C
program. This approach is useful when you only need to insert a small number of instructions. To produce
inline assembly, use the asm macro to insert the given assembly instruction exactly where the asm macro is
located. The example below inserts the instruction ADD R0, R0, R1 into the C program.
int main(void){
/* … */
asm(“ADD R0, R0, R1”);
/* … */
return 0;
}
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EECE 344 Lab 1
Results
Your work for this lab will be evaluated based on:
• Source code (C and assembly) that you submit to Learn
• Demonstration of your working system to your lab TA on the due date
Grading
Your lab will be graded based on:
• 20 points: LCD counter program in C
• 15 points: LED blinking program in ARM assembly
• 15 points: Verilog code for Gray counter
• 10 points: At least a quarter of the header pins soldered to the CPLD board
• 10 points: Code quality and neatness
• 30 points: Demonstration of a working system to your lab TA
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