STK500 UART Test Program (ASM)

UART Test App

This project was created for being able to quickly test and debug the functionality of MCU hardware and wiring of UART applications. This has been fully tested on the STK500 and is fully functional. It should be pretty easy for anyone to alter the speed at which the AVR transmits characters to the PC (even for the newbies). It simply repeatedly cycles through the extended ASCII character set starting from 0x21(!) through 0xFF. Probably not the most efficient code, but I was in a hurry.

Using the 2-wire jumpers, plug the PD0 and PD1 pins into the RXD and TXD pins respectively.

This project was created for being able to quickly test and debug the functionality of MCU hardware and wiring of UART applications. This has been fully tested on the STK500 and is fully functional. It should be pretty easy for anyone to alter the speed at which the AVR transmits characters to the PC (even for the newbies). Probably not the most efficient code, but I was in a hurry.
Using the 2-wire jumpers, plug the PD0 and PD1 pins into the RXD and TXD pins respectively.
Should be able to change the device (i.e. ATmega8535) by simply changing the device include in the source file.

CODE

;*****************************************************************************
;FILENAME: ATmega8 UART TEst App
;AUTHOR: CAS
;COMPANY:
;TARGET DEVICE: ATmega8
;TARGET CLOCK FREQ: 4MHz
;
;DESCRIPTION:
; Tests UART hardware and firmware functionality by cycling through the
; ASCII character set and transmitting each character over RS232 to a PC
; terminal program (most commonly HyperTerminal).
;
;INTERNAL RESOURCES:
; - 2 registers for delay generation
; - 1 register for loop counting
; - 1 register for ASCII value
;
;PERIPHERAL RESOURCES:
; - UART Tx and Rx pins
;
;PIN UTILIZATION:
; - Pin2 - PD0 - Rx
; - Pin3 - PD1 - Tx
;
;CHANGE HISTORY:
; CAS 04Jul2005:
; Started from scratch
;
; CAS 05Jul2005:
; Added Carriage Return and Line Feed loops to insert a blank line
; between each block of ASCII characters. Released source files and
; flash files into directory:
;
;*****************************************************************************

.include "m8def.inc"

;Constants & Expressions
;.ORG $xx
;==============================================================================
.equ ASCII_CHAR_OFFSET =33
.equ BAUD_9600 =25
;.equ
;.equ
;.equ
;.equ
;.equ
;.equ
;.equ
;.equ
;.equ
;.equ
;==============================================================================

;Definitions
;==============================================================================
;.def =r0 ;result byte for 'lpm' and low byte for 'mul' instructions
;.def =r1 ;result high byte for 'mul' instruction
;.def =r2
;.def =r3
;.def =r4
;.def =r5
;.def =r6
;.def =r7
;.def =r8
;.def =r9
;.def =r10
;.def =r11
;.def =r12
;.def =r13
;.def =r14
;.def =r15
.def count0 =r16
.def count1 =r17
.def count2 =r18
.def temp0 =r19
.def temp1 =r20
;.def =r21
;.def =r22
;.def =r23
;.def =r24
;.def =r25
;.def =r26 ;XL by default
;.def =r27 ;XH by default
;.def =r28 ;YL by default
;.def =r29 ;YH by default
;.def =r30 ;ZL by default
;.def =r31 ;ZH by default
;==============================================================================

;***** Variables in SRAM *****
;.dseg
;.ORG $xx ;If necessary
;===================================================================================
;Put SRAM Variable Declarations here
;
;var_name: .BYTE #_of_bytes
;===================================================================================

;***** Program Momory Data *****
;.dseg
;.ORG $xx ;If necessary
;===================================================================================
;Put Constant Declarations here
;
;const_bytes_name:
;.DB 128, 0xFF, 0b01010101;comma-delimited byte values (odd # of bytes results
; ;in compile-time warning)
;
;const_words_name:
;.DW 32768, 0xFFFF, 0b0101010101010101;comma-delimited words
;===================================================================================

;***** Initializations *****
;.cseg
;.ORG $xx ;If necessary
;===================================================================================
;Can put in .inc file for larger applications.
;===================================================================================

;Interrupts
.cseg
;==============================================================================
.org 0x000
rjmp RESET
;.org INT0addr ;External Interrupt 0
; rjmp _INT0
;.org INT1addr ;External Interrupt 1
; rjmp _INT1
;.org OC2addr ;Timer/Counter 2 Compare Interrupt
; rjmp _OC2INT
;.org OVF2addr ;Timer/Counter 2 Overflow Interrupt
; rjmp _OVF2INT
;.org ICP1addr ;Timer/Counter 1 Capture Event Interrupt
; rjmp _ICP1INT
;.org OC1Aaddr ;Timer/Counter 1 Compare Match A Interrupt
; rjmp _OC1AINT
;.org OC1Baddr ;Timer/Counter 1 Compare Match B Interrupt
; rjmp _OC1BINT
;.org OVF1addr ;Timer/Counter 1 Overflow Interrupt
; rjmp _OVF1INT
;.org OVF0addr ;Timer/Counter 0 Overflow Interrupt
; rjmp _OVF0INT
;.org SPIaddr ;Serial Transfer Complete Interrupt
; rjmp _SPIINT
;.org URXCaddr ;USART Rx Complete Interrupt
; rjmp _URXINT
;.org UDREaddr ;USART Data Register Empty Interrupt
; rjmp _EDREINT
;.org UTXCaddr ;USART Tx Complete Interrupt
; rjmp _UTXCINT
;.org ADCCaddr ;A/D Conversion Complete Interrupt
; rjmp _ADCCINT
;.org ERDYaddr ;EEPROM Ready Interrupt
; rjmp _ERDYINT
;.org ACIaddr ;Analog Comparator Interrupt
; rjmp _ACIINT
;.org TWIaddr ;Two-Wire Serial Interface Interrupt
; rjmp _TWIINT
;.org SPMaddr ;Store Program Memory Ready Interrupt
; rjmp _SPMINT
;==============================================================================

.cseg
RESET:
clr count0
clr count1
clr count2

; U2X = 0
; UBRR = [fosc/16*BAUD]-1
rjmp USART_init

TX_ASCII_CHARS:
ldi temp0,ASCII_CHAR_OFFSET
next_ASCII_char:
out UDR,temp0
inc temp0
breq RESTART_TX
rjmp DELAY0

RESTART_TX:
clr count2
ldi temp1,2

; Send Carriage Return
ldi temp0,13
x0:
dec count0
brne x0
dec count1
brne x0
out UDR,temp0

; Send Line Feed
ldi temp0,10
x1:
dec count0
brne x1
dec count1
brne x1
out UDR,temp0

ldi temp0,13
inc count2
cpi count2,2
brne x0

ldi temp0,ASCII_CHAR_OFFSET
rjmp DELAY0

DELAY0:
clr count1
clr count0
dly0:
dec count0
brne dly0
dec count1
brne dly0
rjmp next_ASCII_char

USART_init:
; Set baud rate
ldi temp1,(0<<URSEL)|high(BAUD_9600)
ldi temp0,low(BAUD_9600)
out UBRRH,temp1
out UBRRL,temp0
; Enable Receiver and Transmitter
ldi temp0,(0<<RXEN)|(1<<TXEN)
out UCSRB,temp0
; Set frame format: 8data, 2stop bit
ldi temp0, (1<<URSEL)|(0<<USBS)|(3<<UCSZ0)
out UCSRC,temp0
rjmp TX_ASCII_CHARS