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CE2801-Workspace/lab5keypad/Src/lcd.s
Trevor Barnes 454bed8831 labs 5 and 6 done
2019-11-14 20:06:51 -06:00

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# lcd.s
# Trevor Barnes
# CE2801-031
# Description: Contains routines for the LCD component
.syntax unified
.cpu cortex-m4
.thumb
.section .text
#Fill in addresses
.equ RCC_BASE, 0x40023800
.equ RCC_AHB1ENR, 0x30
.equ RCC_GPIOAEN, 1<<0
.equ RCC_GPIOCEN, 1<<2
.equ GPIOA_BASE, 0x40020000
.equ GPIOC_BASE, 0x40020800
.equ GPIO_MODER, 0x00
.equ GPIO_ODR, 0x14
.equ GPIO_IDR, 0x10
.equ GPIO_BSRR, 0x18
#What pin is each of these?
.equ RS, 8 // PC8
.equ RW, 9 // PC9
.equ E, 10 // PC10
#Commands for BSRR
.equ RS_SET, 1<<RS
.equ RS_CLR, 1<<(RS+16)
.equ RW_SET, 1<<RW
.equ RW_CLR, 1<<(RW+16)
.equ E_SET, 1<<E
.equ E_CLR, 1<<(E+16)
#Globally exposed functions
.global lcdInit
#Local helper function
PortSetup:
push {r1,r2,r3}
#Turn on Ports in RCC
ldr r1, =RCC_BASE
ldr r2, [r1, #RCC_AHB1ENR]
orr r2, r2, #RCC_GPIOAEN
str r2, [r1, #RCC_AHB1ENR]
ldr r2, [r1, #RCC_AHB1ENR]
orr r2, r2, #RCC_GPIOCEN
str r2, [r1, #RCC_AHB1ENR]
#Set DB Pins to Outputs
ldr r1, =GPIOA_BASE
ldr r2, [r1, #GPIO_MODER]
movw r3, 0x5500
movt r3, 0x0055
orr r2,r2, r3
movw r3, 0xAA00
movt r3, 0x00AA
bic r2, r2, r3
str r2, [r1, #GPIO_MODER]
#Set RS RW E Pins to Outputs
ldr r1, =GPIOC_BASE
ldr r2, [r1, #GPIO_MODER]
movw r3, 0x0000
movt r3, 0x0015
orr r2,r2, r3
movw r3, 0x0000
movt r3, 0x00EA
bic r2, r2, r3
str r2, [r1, #GPIO_MODER]
pop {r1,r2,r3}
bx lr
#Writes instruction
#RS=0 RW=0 R1-Arg
#No returns
WriteInstruction:
push {r2,r3,lr}
#Set RS=0,RW=0,E=0
ldr r2, =GPIOC_BASE
mov r3, RS_CLR
str r3, [r2, #GPIO_BSRR]
mov r3, RW_CLR
str r3, [r2, #GPIO_BSRR]
mov r3, E_CLR
str r3, [r2, #GPIO_BSRR]
#Set E=1
mov r3, E_SET
str r3, [r2, #GPIO_BSRR]
#Set R1 -> DataBus
lsl r1, #4
ldr r3, =GPIOA_BASE
ldr r2, [r3, #GPIO_ODR]
bfc r2, #4, #8
orr r2, r2, r1
str r2, [r3, #GPIO_ODR ]
#Set E=0
ldr r2, =GPIOC_BASE
mov r3, E_CLR
str r3, [r2, #GPIO_BSRR]
#Wait for appropriate delay
mov r1, #37
bl usDelay
pop {r2,r3,pc}
#Writes data
#RS=0 RW=0 R1-Arg
#No returns
WriteData:
push {r1,r2,r3,r4,lr}
#Set RS=1,RW=0,E=0
ldr r2, =GPIOC_BASE
mov r3, #RS_SET
str r3, [r2, #GPIO_BSRR]
mov r3, #RW_CLR
str r3, [r2, #GPIO_BSRR]
mov r3, #E_CLR
str r3, [r2, #GPIO_BSRR]
#Set E=1
mov r3, #E_SET
str r3, [r2, #GPIO_BSRR]
#Set R1 -> DataBus
lsl r1, #4
ldr r3, =GPIOA_BASE
ldr r2, [r3, #GPIO_ODR]
bfc r2, #4, #8
orr r2, r2, r1
str r2, [r3, #GPIO_ODR ]
#Set E=0
ldr r2, =GPIOC_BASE
mov r3, #E_CLR
str r3, [r2, #GPIO_BSRR]
#Wait for appropriate delay
mov r1, #37
bl usDelay
pop {r1,r2,r3,r4,pc}
#Code to intialize the lcd
lcdInit:
push {r0,r1,lr}
#Set up Ports
bl PortSetup
#Wait 40ms
mov r0, #40
bl msDelay
#Write Function Set (0x38)
mov r1, 0x38
bl WriteInstruction
mov r1, #37
bl usDelay
#Write Function Set (0x38)
mov r1, 0x38
bl WriteInstruction
mov r1, #37
bl usDelay
#Write Display On/Off(0x0F)
mov r1, 0x0F
bl WriteInstruction
mov r1, #37
bl usDelay
#Write Display Clear (0x01)
mov r1, 0x01
bl WriteInstruction
mov r1, #2
bl msDelay
#Write Entry Mode Set (0x06)
mov r1, 0x06
bl WriteInstruction
mov r1, #37
bl usDelay
pop {r0,r1,pc}
.global lcdClear
# clears the display
# no arguments or return
# includes necessary delay
lcdClear:
push {r0,r1,lr}
mov r1, 0x01
bl WriteInstruction
# Delay for at least 1.52ms
mov r0, #2
bl msDelay
pop {r0,r1,pc}
.global lcdHome
# moves cursor to the home position
# no arguments or return
# includes necessary delay
lcdHome:
push {r1,lr}
mov r1, #0x02
bl WriteInstruction
mov r0, #2
bl msDelay
pop {r1,pc}
.global lcdSetPosition
# moves cursor to the position indicated
# r0 is the zero-based row and r1 is the zero-based column, no return value
# includes necessary delay
lcdSetPosition:
push {r0,r1,lr}
# Sub values to "actual" positions
sub r0, r0, #1
sub r1, r1, #1
# Shift row to actual
lsl r0, r0, #6
orr r0, r0, r1
mov r1, #0x80
orr r1, r1, r0
bl WriteInstruction
pop {r0,r1,pc}
.global lcdPrintString
# prints a null terminated string to the display
# r0 contains the address of the null terminated string (usually located in .data or .rodata), returns the number of characters written to display in r0
# includes necessary delay
lcdPrintString:
push {r0,r1,r2,r3,lr}
mov r2, #0
loop:
ldrb r1, [r0, r2]
cmp r1, #0x00
beq done
bl WriteData
add r2, r2, #1
b loop
done:
mov r0, r1
pop {r0,r1,r2,r3,pc}
.global lcdPrintNum
# prints a (decimal) number to the display
# the number to be printed is in r0, values of 0 to 9999 will print, anything above 9999 should print Err.
# includes necessary delay
lcdPrintNum:
push {r0,r1,r2,r3,r4,lr}
bl num_to_ASCII
# Store num in memory
ldr r2, =numToPrint
str r0, [r2]
# Move cursor to right-most position
mov r1, #16
writeByte:
mov r0, #1
bl lcdSetPosition
mov r4, r0
mov r0, #1
bl msDelay
mov r0, r4
mov r0, r1
ldrb r1, [r2, r3]
bl WriteData
mov r4, r0
mov r0, #1
bl msDelay
mov r0, r4
add r3, r3, #1
cmp r3, #4
sub r1, r0, #1
cmp r3, #4
bne writeByte
pop {r0,r1,r2,r3,r4,pc}
.global lcdCursorLocation
# Returns the location of the cursor on the LCD (1-32)
# Location of cursor is returned in r0
lcdCursorLocation:
push {r1,lr}
pop {r1,pc}
# Takes in a value from 0-9999 and converts it to ASCII
# Input:
# r0: Input binary value
num_to_ASCII:
# If outside of range, return ASCII "Err."
push {r1,r2,r3,lr}
cmp r0,#0
blt out_of_range
# cmp r0,#9999
# bgt out_of_range
# Normal conversion behavior
mov r1, #16
lsl r0, #3
sub r1, #3
shift_cycle:
lsl r0, #1
sub r1, #1
cmp r1, #0
# Branch to encode section if shifted 16 times
beq encode
# Verify Each Nibble is less than or equal to 4
ubfx r2, r0, #16, #4
# If value is less than or equal to 4, then skip to next nibble
cmp r2, #4
ble 2f
add r2, #3
bfi r0, r2, #16, #4
2: ubfx r2, r0, #20, #4
# If value is less than or equal to 4, then skip to next nibble
cmp r2, #4
ble 3f
add r2, #3
bfi r0, r2, #20, #4
3: ubfx r2, r0, #24, #4
# If value is less than or equal to 4, then skip to next nibble
cmp r2, #4
ble 4f
add r2, #3
bfi r0, r2, #24, #4
4: ubfx r2, r0, #28, #4
# If value is less than or equal to 4 skip to end
cmp r2, #4
ble end_verify_nibbles
add r2, #3
bfi r0, r2, #28, #4
end_verify_nibbles:
b shift_cycle
encode:
mov r3, #3
# Encode BCD numbers to ASCII
# Extract ones nibble
ubfx r2, r0, #16, #4
# Insert ones nibble
bfi r1, r2, #0, #4
# Insert 3 in front of nibble for ASCII encoding
bfi r1, r3, #4, #4
# Extract tens nibble
ubfx r2, r0, #20, #4
# Insert tens nibble
bfi r1, r2, #8, #4
# Insert 3 in front of nibble for ASCII encoding
bfi r1, r3, #12, #4
# Extract hundreds nibble
ubfx r2, r0, #24, #4
# Insert hundreds nibble
bfi r1, r2, #16, #4
# Insert 3 in front of nibble for ASCII encoding
bfi r1, r3, #20, #4
# Extract thousands nibble
ubfx r2, r0, #28, #4
# Insert thousands nibble
bfi r1, r2, #24, #4
# Insert 3 in front of nibble for ASCII encoding
bfi r1, r3, #28, #4
b end_ASCII
out_of_range:
# Insert ASCII "Err."
movw r1, #0x722E
movt r1, #0x4572
end_ASCII:
# Return value in r0
mov r0, r1
pop {r1,r2,r3,pc}
.global lcdBusyWait
# Loops until the busy flag is 0
lcdBusyWait:
push {r0,r1,r2,r3,lr}
ldr r1, =GPIOA_BASE
ldr r2, [r1, #GPIO_MODER]
mov r3, #0
orr r2, r2, r3
movw r3, 0xFF00
movt r3, 0x00FF
bic r2, r2, r3
str r2, [r1, #GPIO_MODER]
#Set RS=0, RW=1, E=1
ldr r2, =GPIOC_BASE
mov r3, #RS_CLR
str r3, [r2, #GPIO_BSRR]
mov r3, #RW_SET
str r3, [r2, #GPIO_BSRR]
mov r3, #E_SET
str r3, [r2, #GPIO_BSRR]
busy:
#Set E=
mov r3, #E_SET
str r3, [r2, #GPIO_BSRR]
#Set Databus -> R1
ldr r3, =GPIOA_BASE
ldr r1, [r3, #GPIO_IDR]
#Set E=0
ldr r2, =GPIOC_BASE
mov r3, #E_CLR
str r3, [r2, #GPIO_BSRR]
mov r2, #0x0010
and r1, r2
lsr r1, #4
# Are we still busy?
cmp r1, #1
beq busy
# Return DB port to original mode
ldr r1, =GPIOA_BASE
ldr r2, [r1, #GPIO_MODER]
movw r3, 0x5500
movt r3, 0x0055
orr r2,r2, r3
movw r3, 0xAA00
movt r3, 0x00AA
bic r2, r2, r3
str r2, [r1, #GPIO_MODER]
pop {r0,r1,r2,r3,pc}
.section .data
numToPrint:
.word 0
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