Started LCD

16x2_lcd/Makefile

@@ -0,0 +1,35 @@
+BINARY=lcd
+
+AS=avr-as
+LD=avr-ld
+OBJCOPY=avr-objcopy
+GDB=avr-gdb
+
+AVRDUDE=avrdude
+AVRDUDE_CONFIG=/etc/avrdude.conf
+
+TTY=/dev/ttyACM0
+
+ARCH=atmega328p
+
+SIMAVR=simavr
+
+build:
+	$(AS) -g -mmcu=$(ARCH) -o $(BINARY).o $(BINARY).s
+	$(LD) -o $(BINARY).elf $(BINARY).o
+	$(OBJCOPY) -O ihex -R .eeprom $(BINARY).elf $(BINARY).hex	
+
+upload:
+	$(AVRDUDE) -C $(AVRDUDE_CONFIG) -p $(ARCH) -c arduino -P $(TTY) -b 115200 -D -U flash:w:$(BINARY).hex:i
+
+sim:
+	$(SIMAVR) -m $(ARCH) $(BINARY).elf -g 
+
+debug:
+	$(GDB) $(BINARY).elf
+
+
+run: build upload
+	
+clean:
+	ls | grep $(BINARY) | grep -v *.s | xargs rm -f --

16x2_lcd/lcd.s

@@ -0,0 +1,55 @@
+.equ RAMEND, 0x08FF
+
+.equ SREG, 0x3F
+.equ SPL,  0x3D
+.equ SPH,  0x3E
+
+.equ PORTD, 0x0B
+.equ DDRD,  0x0A
+
+.equ PORTB, 0x05
+.equ DDRB, 0x04
+
+.equiv PINCONFIG, 24
+
+.org 0x0000
+
+INIT_MEM:
+
+    ; Description:
+    ; -----------
+    ;
+    ;  Reset the system status in SREG, initialize the stack using SPL and 
+    ;  SPH and set output PINs on PORTB. 
+    ;
+    ; Pins used for DATA will be DIGITAL PIN 1-7 from PORTD and DIGITAL PIN 8
+    ; from PORTB.
+    ;
+    ; Pins used for REGISTER SELECT, READ/WRITE and ENABLE are DIGITAL PINS
+    ; 10, 11, respectively 12 from PORTB.
+
+    clr r16
+    out SREG, r16
+
+    ldi r16, lo8(RAMEND)
+    out SPL, r16
+
+    ldi r16, hi8(RAMEND)
+    out SPH, r16
+
+    ldi r16, 0xFE
+    out DDRD, r16
+
+    ldi r16, 0x1C
+    out DDRB, r16
+
+INIT_LCD:
+
+    ldi PINCONFIG, 0x10
+    out PORTB, PINCONFIG
+
+    ldi PINCONFIG, 0x70
+    out PORTD, PINCONFIG
+
+MAIN:
+    rjmp MAIN

7_segment_display/.gdbinit

@@ -8,4 +8,4 @@ disass
 end
 
 # Here you can put a breakpoint to skip some code
-b ENCODE
+b COMPUTED

7_segment_display/README.md

@@ -0,0 +1,22 @@
+7 SEGMENT DISPLAY
+
+segment.s implements the logic behind displaying numbers between 0 and 9 on
+a 7 segment display. The PIN configuration is the following:
+
+  * a - DIGITAL PIN 0
+  * b - DIGITAL PIN 1
+  * c - DIGITAL PIN 2
+  * d - DIGITAL PIN 3
+  * e - DIGITAL PIN 4
+  * f - DIGITAL PIN 5
+  * d - DIGITAL PIN 6
+
+All these PINs are connected on PORTD, so we need to keep that in mind when
+writing our output to the correct PORT.
+
+The boolean formulas used to configure the PINs are calcualted using
+Karnaugh Diagrams. 
+
+As a final word, don't forget to add resistors in series with each display
+PIN, on the breadboard, because I forgot to do so and I completely screwed
+a display.

7_segment_display/segment.s

@@ -13,22 +13,22 @@
 .equ PORTD, 0x0B
 .equ DDRD,  0x0A
 
-; Aliases for registers. It is easier to develop the logic this way.
+; Aliases for registers. ABIT, BBIT, CBIT, DBIT contain the bits in the binary
+; representation of numbers displayed on the 7 segment display. A is the MSB
+; and D is the LSB. RESULT, TEMP1 and EOREG are registers used when computing
+; the boolean functions for each PIN. PINCONFIG is the register that decides
+; which PINs are set when sending voltage to the 7 segment display.
 
 .equiv ABIT, 17
 .equiv BBIT, 18
 .equiv CBIT, 19
 .equiv DBIT, 20
+
 .equiv RESULT, 21
 .equiv TEMP1, 22
-.equiv TEMP2, 23
-
-; Aliases for PINs connected to the 7 segment display. These are the
-; values written in PORTD. DIGITAL PINs 0-6 are connected to PINs a-g
-; of the 7 segment display.
-
-; TO BE IMPLEMENTED
+.equiv EOREG, 23
 
+.equiv PINCONFIG, 30
 
 .org 0x0000
 
@@ -82,11 +82,22 @@ COUNTER:
 
 ENCODE:
 
+    ; Reset PINCONFIG and RESULT registers.
+
+    clr PINCONFIG
+    clr RESULT
+
+    ; Output a blank screen to put some delay between digits, it looks smoother
+    ; this way.
+
+    out PORTD, PINCONFIG
+    call WAIT
+
     ; Description:
     ; -----------
     ;
-    ;  To represent a digit we will use a 4 bit number looking like this DCBA
-    ;  (A is the LSB and D is the MSB). The equations for the 7 segment display
+    ;  To represent a digit we will use a 4 bit number looking like this ABCD
+    ;  (A is the MSB and D is the LSB). The equations for the 7 segment display
     ;  PINs are the following, they can be easily computed using Karnaugh 
     ;  Diagrams:
     ;  
@@ -94,40 +105,52 @@ ENCODE:
     ;  b = !B + !C!D + CD
     ;  c = B + !C + D
     ;  d = !B!D + C!D + B!CD + !BC + A
-    ;  e = !b!d + C!D
+    ;  e = !B!D + C!D
     ;  f = A + !C!D + B!C + B!D
     ;  g = A + B!C + !BC + C!D
     ;
-    ;  Each PIN equation will be computed in r21 and sent to its corresponding 
+    ;  Each PIN equation will be computed in RESULT and sent to its corresponding 
     ;  PIN. Other registers will be used to extract the bits from the binary
     ;  number and to perform logic operations.
 
-    mov ABIT, r24
-    andi ABIT, 0x01
-
-    mov BBIT, r24
-    asr BBIT
-    andi BBIT, 0x01
+    mov DBIT, r24
+    andi DBIT, 0x01
 
     mov CBIT, r24
     asr CBIT
-    asr CBIT
     andi CBIT, 0x01
 
-    mov DBIT, r24
-    asr DBIT
-    asr DBIT
-    asr DBIT
+    mov BBIT, r24
+    asr BBIT
+    asr BBIT
+    andi BBIT, 0x01
+
+    mov ABIT, r24
+    asr ABIT
+    asr ABIT
+    asr ABIT
+
+    ; After shifting each bit in its corresponding register, clear carry flag
+    ; because we will perform multiple ROL's and don't want any additional
+    ; bit coming from Carry in RESULT.
+
+    clc
+
+    ; EOREG will be used for eor'ing with register TEMP1 or RESULT
+    ; It is equivalent with flipping the bit in TEMP1 or RESULT.
+
+    ldi EOREG, 0x01
 
     ; Compute a. Steps:
     ;
-    ; 1. Move A in RESULT and perform OR with C
-    ; 2. Move B in TEMP1 and perform AND with B
-    ; 3. Perform OR between (A + C) and BD
-    ; 4. Move B in TEMP1, perform or with D and negate the result (!B!D = !(B + D))
-    ;    (to negate all the bits we will use exclusive or between the register
-    ;     and the value 0xFF)
-    ; 5. Perform OR between (A + C + BD) and !B!D
+    ; 1. Move A in RESULT
+    ; 2. Perform RESULT = RESULT + C
+    ; 3. Compute DB using TEMP1 and perform RESULT = RESULT + BD
+    ; 4. Compute !D!B = !(D + B) using TEMP1 and EOREG and perform 
+    ;       RESULT = RESULT + !B!D.
+    ; 5. Write RESULT to DIGITAL PIN 0
+
+COMPUTEA:
 
     mov RESULT, ABIT
 
@@ -139,13 +162,222 @@ ENCODE:
 
     mov TEMP1, BBIT
     or TEMP1, DBIT
-    ldi TEMP2, 0xFF
-    eor TEMP1, TEMP2
-    andi TEMP1, 0x01
-    and RESULT, TEMP1
+    eor TEMP1, EOREG
+    or RESULT, TEMP1
+
+    or PINCONFIG, RESULT
+
+    ; Compute b. Steps:
+    ;
+    ; 1. Move B in RESULT and invert the bits.
+    ; 2. Compute !C!D using TEMP1 and EOREG and perform RESULT = RESULT + !C!D
+    ; 3. Compute CD using TEMP1 and perform RESULT = RESULT + CD
+    ; 4. Write RESULT to DIGITAL PIN 1
+
+COMPUTEB:
+
+    mov RESULT, BBIT
+    eor RESULT, EOREG
+
+    mov TEMP1, CBIT
+    or TEMP1, DBIT
+    eor TEMP1, EOREG
+    or RESULT, TEMP1
+
+    mov TEMP1, CBIT
+    and TEMP1, DBIT
+    or RESULT, TEMP1
+
+    rol RESULT
+
+    or PINCONFIG, RESULT
+
+    ; Compute c. Steps:
+    ;
+    ; 1. Move B in RESULT
+    ; 2. Perform RESULT = RESULT + !C
+    ; 3. Perform RESULT = RESULT + D
+    ; 4. Write RESULT to DIGITAL PIN 2
+
+COMPUTEC:
+
+    mov RESULT, BBIT
+
+    mov TEMP1, CBIT
+    eor TEMP1, EOREG
+    or RESULT, TEMP1
+
+    or RESULT, DBIT
+
+    rol RESULT
+    rol RESULT
+
+    or PINCONFIG, RESULT
+
+    ; Compute d. Steps:
+    ;
+    ; 1. Move A int RESULT
+    ; 2. Perform RESULT = RESULT + !B!D
+    ; 3. Perform RESULT = RESULT + C!D
+    ; 4. Perform RESULT = RESULT + B!CD
+    ; 5. Perform RESULT = RESULT + !BC
+    ; 6. Write RESULT to DIGITAL PIN 3
+
+COMPUTED:
+
+    mov RESULT, ABIT
+
+    mov TEMP1, BBIT
+    or TEMP1, DBIT
+    eor TEMP1, EOREG
+    or RESULT, TEMP1
+
+    mov TEMP1, DBIT
+    eor TEMP1, EOREG
+    and TEMP1, CBIT
+    or RESULT, TEMP1
+
+    mov TEMP1, CBIT
+    eor TEMP1, EOREG
+    and TEMP1, BBIT
+    and TEMP1, DBIT
+    or RESULT, TEMP1
+
+    mov TEMP1, BBIT
+    eor TEMP1, EOREG
+    and TEMP1, CBIT
+    or RESULT, TEMP1
+
+    rol RESULT
+    rol RESULT
+    rol RESULT
+
+    or PINCONFIG, RESULT
+
+    ; Compute e. Steps:
+    ;
+    ; 1. Compute RESULT = C!D
+    ; 2. Compute RESULT = RESULT + !B!D
+    ; 3. Write RESULT to DIGITAL PIN 4
+
+COMPUTEE:
+
+    mov RESULT, DBIT
+    eor RESULT, EOREG
+    and RESULT, CBIT
+
+    mov TEMP1, BBIT
+    or TEMP1, DBIT
+    eor TEMP1, EOREG
+    or RESULT, TEMP1
+
+    rol RESULT
+    rol RESULT
+    rol RESULT
+    rol RESULT
+
+    or PINCONFIG, RESULT
+
+    ; Compute f. Steps:
+    ;
+    ; 1. Compute RESULT = A
+    ; 2. Compute RESULT = RESULT + !C!D
+    ; 3. Compute RESULT = RESULT + B!C
+    ; 4. Compute RESULT = RESULT + B!D
+    ; 5. Write RESULT to DIGITAL PIN 5
+
+COMPUTEF:
+
+    mov RESULT, ABIT
+
+    mov TEMP1, CBIT
+    or TEMP1, DBIT
+    eor TEMP1, EOREG
+    or RESULT, TEMP1
+
+    mov TEMP1, CBIT
+    eor TEMP1, EOREG
+    and TEMP1, BBIT
+    or RESULT, TEMP1
+
+    mov TEMP1, DBIT
+    eor TEMP1, EOREG
+    and TEMP1, BBIT
+    or RESULT, TEMP1
+
+    rol RESULT
+    rol RESULT
+    rol RESULT
+    rol RESULT
+    rol RESULT
+
+    or PINCONFIG, RESULT
+
+    ; Compute g. Steps:
+    ;
+    ; 1. Compute RESULT = B!C
+    ; 2. Compute RESULT = RESULT + !BC
+    ; 3. Compute RESULT = RESULT + C!D
+    ; 4. Compute RESULT = RESULT + A
+    ; 5. Write RESULT to DIGITAL PIN 6
+
+COMPUTEG:
+
+    mov RESULT, CBIT
+    eor RESULT, EOREG
+    and RESULT, BBIT
+
+    mov TEMP1, BBIT
+    eor TEMP1, EOREG
+    and TEMP1, CBIT
+    or RESULT, TEMP1
+
+    mov TEMP1, DBIT
+    eor TEMP1, EOREG
+    and TEMP1, CBIT
+    or RESULT, TEMP1
+
+    or RESULT, ABIT
+
+    rol RESULT
+    rol RESULT
+    rol RESULT
+    rol RESULT
+    rol RESULT
+    rol RESULT
+
+    or PINCONFIG, RESULT
+
+WRITE_RESULT:
+
+    out PORTD, PINCONFIG
 
     ret
 
 WAIT:
 
+    ; Description
+    ; -----------
+    ;
+    ; Loop 0x{r17, r18, r19} times (for example 0x300000) times because the
+    ; internal clock of the board is to fast and the digits cannot be seen.
+    ; We know that 0x400000 iterations take approximately 0.7s so we can make
+    ; further calcualtions based on this (or by looking in the instruction set
+    ; at the clock cycles taken by each instruction used in the loop).
+
+    ldi r17, 0x30
+    ldi r18, 0x00
+    ldi r19, 0x00
+
+_WAIT:
+
+    dec r19
+    brne _WAIT
+
+    dec r18
+    brne _WAIT
+
+    dec r17
+    brne _WAIT
+
     ret