From 3524892f801830708ccd13d2a90c622555bc6f11 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Tue, 28 Nov 2023 17:45:20 -0800
Subject: [PATCH 1/8] Add quick uart irq test

---
 hw/efinix_fpga/simulation/Makefile            |  2 +-
 .../simulation/tbs/uart_irq_code_tb.sv        | 36 ++++++++++++++++
 sw/test_code/uart_irq_test/Makefile           | 42 +++++++++++++++++++
 sw/test_code/uart_irq_test/link.ld            | 35 ++++++++++++++++
 sw/test_code/uart_irq_test/main.s             | 35 ++++++++++++++++
 sw/test_code/uart_irq_test/vectors.s          | 14 +++++++
 6 files changed, 163 insertions(+), 1 deletion(-)
 create mode 100644 hw/efinix_fpga/simulation/tbs/uart_irq_code_tb.sv
 create mode 100644 sw/test_code/uart_irq_test/Makefile
 create mode 100644 sw/test_code/uart_irq_test/link.ld
 create mode 100644 sw/test_code/uart_irq_test/main.s
 create mode 100644 sw/test_code/uart_irq_test/vectors.s

diff --git a/hw/efinix_fpga/simulation/Makefile b/hw/efinix_fpga/simulation/Makefile
index 63fa1ed..b304dde 100644
--- a/hw/efinix_fpga/simulation/Makefile
+++ b/hw/efinix_fpga/simulation/Makefile
@@ -11,7 +11,7 @@ TEST_PROGRAM?=$(REPO_TOP)/sw/test_code/$(TEST_PROGRAM_NAME)/$(TEST_PROGRAM_NAME)
 
 STANDALONE_TB= interrupt_controller_tb mapper_tb rtc_tb uart_irq_tb
 CODE_TB= interrupt_controller_code_tb mapper_code_tb rtc_code_tb \
-		devices_setup_code_tb
+		devices_setup_code_tb uart_irq_code_tb
 
 #TODO implement something like sources.list
 
diff --git a/hw/efinix_fpga/simulation/tbs/uart_irq_code_tb.sv b/hw/efinix_fpga/simulation/tbs/uart_irq_code_tb.sv
new file mode 100644
index 0000000..4c63a70
--- /dev/null
+++ b/hw/efinix_fpga/simulation/tbs/uart_irq_code_tb.sv
@@ -0,0 +1,36 @@
+`timescale 1ns/1ps
+
+module uart_irq_code_tb();
+
+sim_top u_sim_top();
+
+always begin
+    if (
+        u_sim_top.w_cpu_addr == 16'h0 &&
+        u_sim_top.w_cpu_we == '1
+    ) begin
+        if (u_sim_top.w_cpu_data_from_cpu == 8'h6d) begin
+            $display("Good finish!");
+            $finish();
+        end else begin
+            $display("Bad finish!");
+            $finish_and_return(-1);
+        end
+    end
+    # 1;
+end
+
+initial begin
+    repeat(15000) @(posedge u_sim_top.r_clk_cpu)
+    u_sim_top.u_sim_uart.tx_en = 1;
+    @(posedge u_sim_top.r_clk_cpu);
+    u_sim_top.u_sim_uart.tx_data = 8'hAA;
+    repeat (100) @(posedge u_sim_top.r_clk_cpu);
+    $finish();
+end
+
+always @(u_sim_top.u_dut.u_rtc.r_output) begin
+    $display("counter: %d", u_sim_top.u_dut.u_rtc.r_output);
+end
+
+endmodule
\ No newline at end of file
diff --git a/sw/test_code/uart_irq_test/Makefile b/sw/test_code/uart_irq_test/Makefile
new file mode 100644
index 0000000..9e16104
--- /dev/null
+++ b/sw/test_code/uart_irq_test/Makefile
@@ -0,0 +1,42 @@
+CC=../../cc65/bin/cl65
+LD=../../cc65/bin/cl65
+CFLAGS=-T -t none -I. --cpu "65C02"
+LDFLAGS=-C link.ld -m $(NAME).map
+
+NAME=uart_irq_test
+
+DEVICES=$(REPO_TOP)/sw/kernel/devices
+
+BIN=$(NAME).bin
+HEX=$(NAME).hex
+
+LISTS=lists
+
+SRCS=$(wildcard *.s) $(wildcard *.c)
+SRCS+=$(DEVICES)/interrupt_controller.s
+SRCS+=$(wildcard **/*.s) $(wildcard **/*.c)
+OBJS+=$(patsubst %.s,%.o,$(filter %s,$(SRCS)))
+OBJS+=$(patsubst %.c,%.o,$(filter %c,$(SRCS)))
+
+# Make sure the kernel linked to correct address, no relocation!
+all: $(HEX)
+
+$(HEX): $(BIN)
+	objcopy --input-target=binary --output-target=verilog $(BIN) $(HEX)
+
+$(BIN): $(OBJS)
+	$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) -o $@
+
+%.o: %.c $(LISTS)
+	$(CC) $(CFLAGS) -l $(LISTS)/$<.list -c $< -o $@
+
+%.o: %.s $(LISTS)
+	$(CC) $(CFLAGS) -l $(LISTS)/$<.list -c $< -o $@
+
+$(LISTS):
+	mkdir -p $(addprefix $(LISTS)/,$(sort $(dir $(SRCS))))
+
+.PHONY: clean
+clean:
+	rm -rf $(OBJS) $(BIN) $(HEX) $(LISTS) $(NAME).map
+
diff --git a/sw/test_code/uart_irq_test/link.ld b/sw/test_code/uart_irq_test/link.ld
new file mode 100644
index 0000000..66a42fe
--- /dev/null
+++ b/sw/test_code/uart_irq_test/link.ld
@@ -0,0 +1,35 @@
+MEMORY
+{
+  ZP:  start = $0,    size = $100,  type = rw, define = yes;
+  SDRAM: start = $9200, size = $4d00, type = rw, define = yes;
+  ROM: start = $F000, size = $1000, file = %O;
+}
+
+SEGMENTS {
+    ZEROPAGE: load = ZP,  type = zp,  define   = yes;
+    DATA:     load = ROM, type = rw,  define   = yes, run = SDRAM;
+    BSS:      load = SDRAM, type = bss, define   = yes;
+    HEAP:     load = SDRAM, type = bss, optional = yes;
+    STARTUP:  load = ROM, type = ro;
+    ONCE:     load = ROM, type = ro,  optional = yes;
+    CODE:     load = ROM, type = ro;
+    RODATA:   load = ROM, type = ro;
+    VECTORS:  load = ROM, type = ro,  start    = $FFFA;
+}
+
+FEATURES {
+    CONDES:    segment = STARTUP,
+               type    = constructor,
+               label   = __CONSTRUCTOR_TABLE__,
+               count   = __CONSTRUCTOR_COUNT__;
+    CONDES:    segment = STARTUP,
+               type    = destructor,
+               label   = __DESTRUCTOR_TABLE__,
+               count   = __DESTRUCTOR_COUNT__;
+}
+
+SYMBOLS {
+    # Define the stack size for the application
+    __STACKSIZE__:  value = $0200, type = weak;
+    __STACKSTART__: type = weak, value = $0800; # 2k stack
+}
diff --git a/sw/test_code/uart_irq_test/main.s b/sw/test_code/uart_irq_test/main.s
new file mode 100644
index 0000000..9ce4fbb
--- /dev/null
+++ b/sw/test_code/uart_irq_test/main.s
@@ -0,0 +1,35 @@
+.export _init, nmi_int, irq_int
+
+.autoimport
+
+.import _init_interrupt_controller
+
+.zeropage
+
+finish: .res 1
+
+.code
+
+nmi_int:
+irq_int:
+    lda #$6d
+    sta $00
+
+_init:
+    ldx #$ff
+    txs
+
+    LDA     #<(__STACKSTART__ + __STACKSIZE__)
+    STA     sp
+    LDA     #>(__STACKSTART__ + __STACKSIZE__)
+    STA     sp+1
+
+    ; enable interrupt 0
+    lda #$00
+    jsr pusha
+    lda #$1
+    jsr _enable_irq
+
+    cli
+
+@end:   bra @end
\ No newline at end of file
diff --git a/sw/test_code/uart_irq_test/vectors.s b/sw/test_code/uart_irq_test/vectors.s
new file mode 100644
index 0000000..73c2865
--- /dev/null
+++ b/sw/test_code/uart_irq_test/vectors.s
@@ -0,0 +1,14 @@
+; ---------------------------------------------------------------------------
+; vectors.s
+; ---------------------------------------------------------------------------
+;
+; Defines the interrupt vector table.
+
+.import    _init
+.import    nmi_int, irq_int
+
+.segment  "VECTORS"
+
+.addr      nmi_int    ; NMI vector
+.addr      _init       ; Reset vector
+.addr      irq_int    ; IRQ/BRK vector
\ No newline at end of file

From fd9ccdbce47d6d3ca1527626249f80e3689bb617 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Tue, 28 Nov 2023 22:54:26 -0800
Subject: [PATCH 2/8] Add serial driver and irq support

---
 sw/kernel/devices/sd_card.c      | 12 +++-
 sw/kernel/devices/serial.h       | 17 ++++++
 sw/kernel/devices/serial.s       | 94 ++++++++++++++++++++++++++++++++
 sw/kernel/interrupts/interrupt.s |  4 +-
 sw/kernel/kernel.c               | 15 ++++-
 5 files changed, 135 insertions(+), 7 deletions(-)
 create mode 100644 sw/kernel/devices/serial.h
 create mode 100644 sw/kernel/devices/serial.s

diff --git a/sw/kernel/devices/sd_card.c b/sw/kernel/devices/sd_card.c
index 8eaf708..4dd6a4e 100644
--- a/sw/kernel/devices/sd_card.c
+++ b/sw/kernel/devices/sd_card.c
@@ -339,12 +339,16 @@ token = 0xFF - response timeout
 *******************************************************************************/
 uint8_t SD_writeSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *token)
 {
+
+    (void)addr;
+    (void)buf;
+    (void)token;
+
+    /*
     uint16_t readAttempts;
     uint8_t res1, read;
     uint16_t i;
 
-    /*
-
     // set token to none
     *token = 0xFF;
 
@@ -391,9 +395,11 @@ uint8_t SD_writeSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *token)
     spi_deselect(0);
     spi_exchange(0xFF);
 
+    return res1;
+
     */
 
-    return res1;
+    return 0;
 }
 
 /*******************************************************************************
diff --git a/sw/kernel/devices/serial.h b/sw/kernel/devices/serial.h
new file mode 100644
index 0000000..2f85df4
--- /dev/null
+++ b/sw/kernel/devices/serial.h
@@ -0,0 +1,17 @@
+#ifndef _SERIAL_H
+#define _SERIAL_H
+
+#include <stdint.h>
+
+void serial_handle_irq();
+
+void serial_init();
+
+void serial_putc(char c);
+void serial_puts(char* s);
+
+
+char serial_getc();
+char serial_getc_nb();
+
+#endif
\ No newline at end of file
diff --git a/sw/kernel/devices/serial.s b/sw/kernel/devices/serial.s
new file mode 100644
index 0000000..0203826
--- /dev/null
+++ b/sw/kernel/devices/serial.s
@@ -0,0 +1,94 @@
+.MACPACK generic
+
+.autoimport
+
+.import _enable_irq, _send_eoi, _uart_txb_block
+
+.importzp tmp1, ptr1
+
+.export _serial_init
+.export _serial_handle_irq
+
+.export _serial_putc, _serial_puts, _serial_getc, _serial_get_nb
+
+.zeropage
+
+last_char: .res 1
+
+
+.code
+
+UART        = $efe6
+UART_TXB    = UART
+UART_RXB    = UART
+UART_STATUS = UART + 1
+
+; Initialize Serial Port
+; No initialization needed, just register irq handler.
+.proc _serial_init
+        lda #<_serial_handle_irq
+        ldx #>_serial_handle_irq
+        jsr pushax
+        lda #$01
+        jsr _register_irq
+        stz last_char
+        rts
+.endproc
+
+; Serial Port IRQ Handler
+; Get the character and store it.
+.proc _serial_handle_irq
+        lda UART_RXB
+        sta last_char
+        ora #$80        ; set msb
+        jsr _send_eoi
+        rti
+.endproc
+
+; Serial Port Get Character
+; If a character has not been received, block until one is.
+.proc _serial_getc
+L1:     lda last_char
+        bpl L1
+        and #$7f
+        sta last_char
+        rts
+.endproc
+
+; Serial Port Get Character Non-Blocking
+; return last character, even if it has already been read.
+; If the character is new, we still clear the new flag.
+.proc _serial_get_nb
+        lda last_char
+        bpl L1
+        and #$7f
+        sta last_char
+L1:     rts
+.endproc
+
+
+; Serial Port Put Character
+; send a single character over the serial port.
+.proc _serial_putc
+        jsr _uart_txb_block
+        cmp #$0a
+        bne @1
+        lda #$0d
+        jsr _uart_txb_block
+@1:     rts
+.endproc
+
+; Send a string over the serial port. Needs stlen
+.proc _serial_puts
+        sta ptr1                ; Store pointer in ptr1
+        stx ptr1+1  
+        ldy #$00                ; initialize y to 0
+L1:     lda (ptr1),y            ; load character from string
+        beq L2                  ; Quit if NULL
+        jsr _uart_txb_block      ; send character (does not change y or ptr1)
+        iny                     ; increment y
+        bne L1                  ; If Y == 0, increment high byte of pointer
+        inc ptr1+1
+        bne L1                  ; if high byte wraps around, give up
+L2:     rts
+.endproc
\ No newline at end of file
diff --git a/sw/kernel/interrupts/interrupt.s b/sw/kernel/interrupts/interrupt.s
index 0344b0a..ede0000 100644
--- a/sw/kernel/interrupts/interrupt.s
+++ b/sw/kernel/interrupts/interrupt.s
@@ -48,7 +48,7 @@ rti
     sta IRQ_CMD_ADDR
     lda IRQ_DAT_ADDR
     ; shift by 2 (oh so only 128 interrupts are supported lol)
-    lsr
+    asl
     tax
     jmp (irq_table,x)
     ; use that to index jump table
@@ -56,6 +56,7 @@ rti
 
 ; void register_irq(void* addr, uint8_t irqn);
 .proc _register_irq
+    asl
     tax
     jsr popa
     sta irq_table,x
@@ -65,6 +66,7 @@ rti
     lda #$00
     jsr pusha
     txa
+    lsr
     jsr _enable_irq
     rts
 .endproc
diff --git a/sw/kernel/kernel.c b/sw/kernel/kernel.c
index 6441fb3..6870a2e 100644
--- a/sw/kernel/kernel.c
+++ b/sw/kernel/kernel.c
@@ -3,6 +3,7 @@
 #include "interrupts/interrupt.h"
 #include "devices/mapper.h"
 #include "devices/rtc.h"
+#include "devices/serial.h"
 
 
 void handle_rtc_interrupt() {
@@ -14,6 +15,8 @@ void handle_rtc_interrupt() {
 
 int main() {
 
+    uint8_t c;
+
     cputs("Kernel\n");
 
     cputs("Init Mapper\n");
@@ -32,9 +35,15 @@ int main() {
 
     asm volatile("cli");
 
-    // cputs("Initialize Serial\n");
-    // // init_serial();
-    // enable_irq(2, IRQ_EDGE);
+    cputs("Initialize Serial\n");
+    serial_init();
+
+    serial_puts("Hello from serial!\n");
+
+    c = serial_getc();
+
+    serial_puts("Got a character!: ");
+    serial_putc(c);
 
     while(1);
 

From e73d8db74ce9560bd9c701bdc3a455c6deddb9ae Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Tue, 28 Nov 2023 23:23:31 -0800
Subject: [PATCH 3/8] Serial Fix

Fixes a typo with getc_nb, removes the RTC tick code (since we know it
works now and it is clogging up the screen), read characters in a loop
instead of just once.
---
 sw/kernel/devices/serial.s |  6 +++---
 sw/kernel/kernel.c         | 14 +++++++-------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/sw/kernel/devices/serial.s b/sw/kernel/devices/serial.s
index 0203826..89b60c8 100644
--- a/sw/kernel/devices/serial.s
+++ b/sw/kernel/devices/serial.s
@@ -9,7 +9,7 @@
 .export _serial_init
 .export _serial_handle_irq
 
-.export _serial_putc, _serial_puts, _serial_getc, _serial_get_nb
+.export _serial_putc, _serial_puts, _serial_getc, _serial_getc_nb
 
 .zeropage
 
@@ -39,8 +39,8 @@ UART_STATUS = UART + 1
 ; Get the character and store it.
 .proc _serial_handle_irq
         lda UART_RXB
-        sta last_char
         ora #$80        ; set msb
+        sta last_char
         jsr _send_eoi
         rti
 .endproc
@@ -58,7 +58,7 @@ L1:     lda last_char
 ; Serial Port Get Character Non-Blocking
 ; return last character, even if it has already been read.
 ; If the character is new, we still clear the new flag.
-.proc _serial_get_nb
+.proc _serial_getc_nb
         lda last_char
         bpl L1
         and #$7f
diff --git a/sw/kernel/kernel.c b/sw/kernel/kernel.c
index 6870a2e..6c67395 100644
--- a/sw/kernel/kernel.c
+++ b/sw/kernel/kernel.c
@@ -8,7 +8,7 @@
 
 void handle_rtc_interrupt() {
     // cputs("In IRQ interrupt!\n");
-    cputc('A');
+    // cputc('A');
     send_eoi();
     asm volatile ("rti");
 }
@@ -40,12 +40,12 @@ int main() {
 
     serial_puts("Hello from serial!\n");
 
-    c = serial_getc();
-
-    serial_puts("Got a character!: ");
-    serial_putc(c);
-
-    while(1);
+    while(1) {
+        c = serial_getc();
+        serial_puts("Got a character!: ");
+        serial_putc(c);
+        serial_putc('\n');
+    }
 
     return 0;
 }

From 5b6a4e14421a2702437adc1a4ae7defa815659f8 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Tue, 28 Nov 2023 23:52:27 -0800
Subject: [PATCH 4/8] Start terminal driver

---
 sw/kernel/devices/terminal.h | 13 ++++++++++++
 sw/kernel/devices/terminal.s | 41 ++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 sw/kernel/devices/terminal.h
 create mode 100644 sw/kernel/devices/terminal.s

diff --git a/sw/kernel/devices/terminal.h b/sw/kernel/devices/terminal.h
new file mode 100644
index 0000000..42a9864
--- /dev/null
+++ b/sw/kernel/devices/terminal.h
@@ -0,0 +1,13 @@
+#ifndef _TERMINAL_H
+#define _TERMINAL_H
+
+#include <stdint.h>
+
+int8_t terminal_read(uint8_t fd, void* buf, uint8_t nbytes);
+int8_t terminal_write(uint8_t fd, const void* buf, uint8_t nbytes);
+int8_t terminal_open(const uint8_t* filename);
+int8_t terminal_close(uint8_t fd);
+
+
+#endif /* _TERMINAL_H */
+
diff --git a/sw/kernel/devices/terminal.s b/sw/kernel/devices/terminal.s
new file mode 100644
index 0000000..56351cb
--- /dev/null
+++ b/sw/kernel/devices/terminal.s
@@ -0,0 +1,41 @@
+.MACPACK generic
+
+.autoimport
+
+.export _terminal_read, _terminal_write, _terminal_open, _terminal_close
+
+.data
+
+terminal_buf: .res 128
+
+.code
+
+.proc _terminal_read
+
+.endproc
+
+.proc _terminal_write
+
+.endproc
+
+; terminal_open
+; open terminal device
+; Inputs: uint8_t* filename
+; Outputs: none
+; Return Value: 0 on success
+; Function: none.
+.proc _terminal_open
+    lda #$0
+    rts
+.endproc
+
+; terminal_close
+; close terminal device
+; Inputs: int32_t fd
+; Outputs: none
+; Return Value: 0 on success (but this always failes)
+; Function: none.
+.proc _terminal_close
+    lda #$ff    ; -1
+    rts
+.endproc
\ No newline at end of file

From b25d0e9bdb951d7d2174a60ca6062c1893574c4f Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Wed, 29 Nov 2023 08:38:25 -0800
Subject: [PATCH 5/8] First shot at terminal read

---
 sw/kernel/devices/terminal.s | 82 ++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/sw/kernel/devices/terminal.s b/sw/kernel/devices/terminal.s
index 56351cb..8afec0f 100644
--- a/sw/kernel/devices/terminal.s
+++ b/sw/kernel/devices/terminal.s
@@ -2,6 +2,9 @@
 
 .autoimport
 
+.importzp tmp1, ptr1
+
+.import _serial_getc
 .export _terminal_read, _terminal_write, _terminal_open, _terminal_close
 
 .data
@@ -10,10 +13,89 @@ terminal_buf: .res 128
 
 .code
 
+; int8_t terminal_read(uint8_t fd, void* buf, uint8_t nbytes);
+; Read up to size-1 (127 max) before the enter key is pressed.
+; A newline character is automatically added.
+; Inputs: int8_t* buf - where input characters are stored
+;         uint8_t n - number of characters to read (max buf size minux 1)
+; Return Value: number of characters read on success, -1 on failure
+; Function: Reads keyboard input
 .proc _terminal_read
+        cmp #$00            ; Check that nbytes is > 0 and < 128
+        beq FAIL
+        cmp #$80
+        bge FAIL
+        sta tmp1            ; Store nbytes in tmp1
+        
+        jsr pushax          ; Check that buf != NULL
+        cmp #$00
+        bne L1
+        cpx #$00
+        bne L1
+        bra FAIL
 
+
+        ; while i < nbytes, store getc into terminal_buf y
+L1:     sta ptr1    
+        stx ptr1+1
+        ldy #$00
+LOOP:   cpy tmp1
+        bge END
+        jsr _serial_getc
+        sta terminal_buf,y
+
+        cmp #$0a            ; If newline, do something
+        bne L2
+        jsr _serial_putc
+        bra END
+
+L2:     cmp #$08            ; Handle backspace
+        bne L3
+        lda tmp1
+        beq LOOP
+        lda #$08
+        jsr _serial_putc
+        dey
+        lda #$00
+        sta terminal_buf,y
+        bra LOOP
+
+L3:     lda terminal_buf,y  ; Normal character
+        sta (tmp1),y
+        jsr _serial_putc
+        iny
+        bra LOOP
+
+END:    phy                 ; Zero out terminal buffer
+        ldy #$00
+        lda #$00
+L4:     sta terminal_buf,y
+        iny
+        cpy #$80
+        blt L4
+
+L5:     ply                 ; End string with NULL
+        lda #$0a
+        sta (ptr1),y
+        iny
+        cpy #$80            ; But not if we are at max
+        bge L6
+        lda #$00
+        sta (ptr1),y
+
+L6:     lda #$00            ; Return - on success
+        rts
+
+FAIL:   lda #$ff            ; return -1 on fail
+        rts
 .endproc
 
+; terminal_write
+; write characters to the terminal
+; Inputs: int8_t* buf - buffer of characters to write
+;         uint8_t n - number of characters to write
+; Return Value: 0 on success, -1 on failure
+; Writes to screen. Only stops after n chars written.
 .proc _terminal_write
 
 .endproc

From 597d15e2341f2a99ba8e699584cef4731583599b Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Wed, 29 Nov 2023 17:19:18 -0800
Subject: [PATCH 6/8] Add terminal write as well, use it in kernel

---
 sw/kernel/devices/terminal.s | 24 ++++++++++++++++++++++--
 sw/kernel/kernel.c           | 18 ++++++++++++------
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/sw/kernel/devices/terminal.s b/sw/kernel/devices/terminal.s
index 8afec0f..ea1f0d0 100644
--- a/sw/kernel/devices/terminal.s
+++ b/sw/kernel/devices/terminal.s
@@ -27,7 +27,7 @@ terminal_buf: .res 128
         bge FAIL
         sta tmp1            ; Store nbytes in tmp1
         
-        jsr pushax          ; Check that buf != NULL
+        jsr popax          ; Check that buf != NULL
         cmp #$00
         bne L1
         cpx #$00
@@ -90,14 +90,34 @@ FAIL:   lda #$ff            ; return -1 on fail
         rts
 .endproc
 
-; terminal_write
+; int8_t terminal_write(uint8_t fd, const void* buf, uint8_t nbytes);
 ; write characters to the terminal
 ; Inputs: int8_t* buf - buffer of characters to write
 ;         uint8_t n - number of characters to write
 ; Return Value: 0 on success, -1 on failure
 ; Writes to screen. Only stops after n chars written.
+; This seems to not care about null termination?
 .proc _terminal_write
+        sta tmp1            ; put nbytes in tmp1
 
+        jsr popax           ; check that buf is not null
+        cmp #$00
+        bne L1
+        cpx #$00
+        bne L1
+        bra FAIL
+L1:
+        ldy #$00
+LOOP:   lda (ptr1),y        ; Loop through buffer and print
+        jsr _serial_putc
+        iny
+        cmp tmp1
+        blt LOOP
+        lda #$00
+        rts
+
+FAIL:   lda #$ff            ; old code didn't fail, but new code does.
+        rts
 .endproc
 
 ; terminal_open
diff --git a/sw/kernel/kernel.c b/sw/kernel/kernel.c
index 6c67395..bbdc685 100644
--- a/sw/kernel/kernel.c
+++ b/sw/kernel/kernel.c
@@ -1,10 +1,14 @@
 #include <conio.h>
+#include <string.h>
+
 #include "devices/interrupt_controller.h"
 #include "interrupts/interrupt.h"
 #include "devices/mapper.h"
 #include "devices/rtc.h"
 #include "devices/serial.h"
 
+#include "devices/terminal.h"
+
 
 void handle_rtc_interrupt() {
     // cputs("In IRQ interrupt!\n");
@@ -13,9 +17,9 @@ void handle_rtc_interrupt() {
     asm volatile ("rti");
 }
 
-int main() {
+char buf[128];
 
-    uint8_t c;
+int main() {
 
     cputs("Kernel\n");
 
@@ -40,11 +44,13 @@ int main() {
 
     serial_puts("Hello from serial!\n");
 
+    terminal_open(NULL);
+    terminal_write(0, "Terminal Write\n", 15);
+
     while(1) {
-        c = serial_getc();
-        serial_puts("Got a character!: ");
-        serial_putc(c);
-        serial_putc('\n');
+        terminal_read(0, buf, 128);
+        terminal_write(0, "Got: ", 5);
+        terminal_write(0, buf, strlen(buf));
     }
 
     return 0;

From a169b30028041816ce46ff821b16a04940aad5c6 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Thu, 30 Nov 2023 23:57:58 -0800
Subject: [PATCH 7/8] Fix not saving to ptr1 and comparing y

---
 sw/kernel/devices/terminal.s | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sw/kernel/devices/terminal.s b/sw/kernel/devices/terminal.s
index ea1f0d0..4245a33 100644
--- a/sw/kernel/devices/terminal.s
+++ b/sw/kernel/devices/terminal.s
@@ -106,12 +106,13 @@ FAIL:   lda #$ff            ; return -1 on fail
         cpx #$00
         bne L1
         bra FAIL
-L1:
+L1:     sta ptr1
+        stx ptr1+1
         ldy #$00
 LOOP:   lda (ptr1),y        ; Loop through buffer and print
         jsr _serial_putc
         iny
-        cmp tmp1
+        cpy tmp1
         blt LOOP
         lda #$00
         rts

From 32c82044a7adb876b5ab53951afb09f1200aa3c4 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Fri, 1 Dec 2023 00:56:16 -0800
Subject: [PATCH 8/8] Fix more bugs

---
 sw/kernel/devices/serial.s   |  2 +-
 sw/kernel/devices/terminal.s |  7 ++++---
 sw/kernel/kernel.c           | 17 ++++++++++-------
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/sw/kernel/devices/serial.s b/sw/kernel/devices/serial.s
index 89b60c8..fe4f024 100644
--- a/sw/kernel/devices/serial.s
+++ b/sw/kernel/devices/serial.s
@@ -85,7 +85,7 @@ L1:     rts
         ldy #$00                ; initialize y to 0
 L1:     lda (ptr1),y            ; load character from string
         beq L2                  ; Quit if NULL
-        jsr _uart_txb_block      ; send character (does not change y or ptr1)
+        jsr _serial_putc        ; send character (does not change y or ptr1)
         iny                     ; increment y
         bne L1                  ; If Y == 0, increment high byte of pointer
         inc ptr1+1
diff --git a/sw/kernel/devices/terminal.s b/sw/kernel/devices/terminal.s
index 4245a33..0604719 100644
--- a/sw/kernel/devices/terminal.s
+++ b/sw/kernel/devices/terminal.s
@@ -23,7 +23,7 @@ terminal_buf: .res 128
 .proc _terminal_read
         cmp #$00            ; Check that nbytes is > 0 and < 128
         beq FAIL
-        cmp #$80
+        cmp #$81
         bge FAIL
         sta tmp1            ; Store nbytes in tmp1
         
@@ -44,8 +44,9 @@ LOOP:   cpy tmp1
         jsr _serial_getc
         sta terminal_buf,y
 
-        cmp #$0a            ; If newline, do something
+        cmp #$0d            ; If newline, do something
         bne L2
+        lda #$0a            ; hacky serial, we want $0a, not $0d
         jsr _serial_putc
         bra END
 
@@ -61,7 +62,7 @@ L2:     cmp #$08            ; Handle backspace
         bra LOOP
 
 L3:     lda terminal_buf,y  ; Normal character
-        sta (tmp1),y
+        sta (ptr1),y
         jsr _serial_putc
         iny
         bra LOOP
diff --git a/sw/kernel/kernel.c b/sw/kernel/kernel.c
index bbdc685..035f0f1 100644
--- a/sw/kernel/kernel.c
+++ b/sw/kernel/kernel.c
@@ -20,26 +20,25 @@ void handle_rtc_interrupt() {
 char buf[128];
 
 int main() {
-
     cputs("Kernel\n");
 
-    cputs("Init Mapper\n");
+    // cputs("Init Mapper\n");
     init_mapper();
 
-    cputs("Initialize Interrupts\n");
+    // cputs("Initialize Interrupts\n");
     init_interrupts();
 
-    cputs("Initialize Interrupt Controller\n");
+    // cputs("Initialize Interrupt Controller\n");
     init_interrupt_controller();
 
-    cputs("Initialize RTC\n");
+    // cputs("Initialize RTC\n");
     init_rtc();
 
     register_irq(&handle_rtc_interrupt, 0);
 
     asm volatile("cli");
 
-    cputs("Initialize Serial\n");
+    // cputs("Initialize Serial\n");
     serial_init();
 
     serial_puts("Hello from serial!\n");
@@ -48,9 +47,13 @@ int main() {
     terminal_write(0, "Terminal Write\n", 15);
 
     while(1) {
-        terminal_read(0, buf, 128);
+        if (terminal_read(0, buf, 128)) {
+            cprintf("Fail\n");
+            break;
+        }
         terminal_write(0, "Got: ", 5);
         terminal_write(0, buf, strlen(buf));
+        terminal_write(0, "\n", 1);
     }
 
     return 0;