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/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..fe4f024
--- /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_getc_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
+        ora #$80        ; set msb
+        sta last_char
+        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_getc_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 _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
+        bne L1                  ; if high byte wraps around, give up
+L2:     rts
+.endproc
\ No newline at end of file
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..0604719
--- /dev/null
+++ b/sw/kernel/devices/terminal.s
@@ -0,0 +1,145 @@
+.MACPACK generic
+
+.autoimport
+
+.importzp tmp1, ptr1
+
+.import _serial_getc
+.export _terminal_read, _terminal_write, _terminal_open, _terminal_close
+
+.data
+
+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 #$81
+        bge FAIL
+        sta tmp1            ; Store nbytes in tmp1
+        
+        jsr popax          ; 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 #$0d            ; If newline, do something
+        bne L2
+        lda #$0a            ; hacky serial, we want $0a, not $0d
+        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 (ptr1),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
+
+; 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:     sta ptr1
+        stx ptr1+1
+        ldy #$00
+LOOP:   lda (ptr1),y        ; Loop through buffer and print
+        jsr _serial_putc
+        iny
+        cpy tmp1
+        blt LOOP
+        lda #$00
+        rts
+
+FAIL:   lda #$ff            ; old code didn't fail, but new code does.
+        rts
+.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
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..035f0f1 100644
--- a/sw/kernel/kernel.c
+++ b/sw/kernel/kernel.c
@@ -1,31 +1,37 @@
 #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");
-    cputc('A');
+    // cputc('A');
     send_eoi();
     asm volatile ("rti");
 }
 
-int main() {
+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);
@@ -33,10 +39,22 @@ int main() {
     asm volatile("cli");
 
     // cputs("Initialize Serial\n");
-    // // init_serial();
-    // enable_irq(2, IRQ_EDGE);
+    serial_init();
 
-    while(1);
+    serial_puts("Hello from serial!\n");
+
+    terminal_open(NULL);
+    terminal_write(0, "Terminal Write\n", 15);
+
+    while(1) {
+        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;
 }
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