More rrxing2 work

1 files changed, 24 insertions, 0 deletions

diff --git a/assembly/rrxing2/util.S b/assembly/rrxing2/util.S
index 9dda1ab..4d55c6b 100644
--- a/assembly/rrxing2/util.S
+++ b/assembly/rrxing2/util.S
@@ -1,3 +1,8 @@
+# Railroad Crossing 2 for RVController - Utility Functions and Macros
+# A product of Scheiße & Broken Signalling Systems, a Cheapie Systems company
+# This is free and unencumbered software released into the public domain.
+# See http://unlicense.org/ for more information
+
 .macro digiline_send channel msg
 	la a0,(\channel)
 	la a1,(\msg)
@@ -33,6 +38,7 @@
 .endm
 
 set_timer:
+# Expects a number of seconds in a0
 li t0,0x80
 csrs mie,t0 # unmask timer interrupt
 ld t1,2(gp) # read mtime
@@ -41,3 +47,21 @@ sltu t0,t1,a0 # check if it overflowed
 add t2,t2,t0 # add the overflow into the high half if there was any
 sd t1,10(gp) # set mtimecmp to the target value
 ret
+
+hexdump:
+# Expects a pointer to the output location in a0 and a number in a1, always outputs 8 digits
+li t0,7
+1: li t1,0xf
+slli t2,t0,2 # Multiply digit number by 4 to get shift amount
+sll t1,t1,t2 # Shift mask over to the necessary digit
+and t1,t1,a1 # Get the necessary digit
+srl t1,t1,t2 # Move it to the ones place
+addi t1,t1,0x30 # Try converting it to an ASCII digit
+li t2,0x3a
+blt t1,t2,2f # If it's out of range...
+addi t1,t1,7 # ...turn it into a letter
+2: sb t1,0(a0) # Write out the digit
+addi a0,a0,1 # Advance the pointer
+addi t0,t0,-1
+bgez t0,1b
+ret