1 files changed, 53 insertions, 0 deletions
diff --git a/kernel/drivers/uart.S b/kernel/drivers/uart.S
new file mode 100644
index 0000000..38957c2
--- /dev/null
+++ b/kernel/drivers/uart.S
@@ -0,0 +1,53 @@
+.section ".text"
+
+.globl uart_char
+uart_char:
+	mov r2, #0x1000
+	movt r2, #0x3f20
+1:
+	ldr r3, [r2, #24]
+	tst r3, #0b100000
+	bne 1b
+	str r0, [r2]
+	bx lr
+
+.globl uart_string
+uart_string:
+	push    {r4, lr}
+	mov     r4, r0
+	ldrb    r0, [r0]
+	cmp     r0, #0
+	popeq   {r4, pc}
+1:
+	bl      uart_char
+	ldrb    r0, [r4, #1]!
+	cmp     r0, #0
+	bne 1b
+	pop     {r4, pc}
+
+.globl uart_hex
+uart_hex:
+	push {r4, lr}
+	mov r2, #0x1000
+	movt r2, #0x3f20
+1:
+	ldr r3, [r2, #24]
+	tst r3, #0b100000
+	bne 1b
+	mov r3, #7
+2:
+	mov r1, r0
+	asr r1, r3
+	asr r1, r3
+	asr r1, r3
+	asr r1, r3
+	and r1, #0xf
+	add r1, #0x30
+	cmp r1, #0x3A
+	blt 3f
+	add r1, #7
+3:
+	str r1, [r2]
+	subs r3, #1
+	bge 2b // Jump back to wait for availablilty
+	pop {r4, pc}