From 6502be88d94aa1d5e3949832c12f47deb8329a4c Mon Sep 17 00:00:00 2001
From: Silvan Jegen <s.jegen@gmail.com>
Date: Sat, 17 Aug 2019 17:54:22 +0200
Subject: Call delay in ISR

---
 software/first/setup_timer_irq.S | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/software/first/setup_timer_irq.S b/software/first/setup_timer_irq.S
index 97b5f6c..c3e7513 100644
--- a/software/first/setup_timer_irq.S
+++ b/software/first/setup_timer_irq.S
@@ -13,7 +13,7 @@ setup_timer_irq:
 	csrw mtvec, t0      # write handler address and mode
 
   # Here we cannot use csrsi because it can only set up to 5 bits
-	li t0, 0x80     # set 7th bit (indexed from 0)
+	li t0, 0x88     # set 4rd and 8th bit
 	csrw mie, t0    # activate machine timer interrupt
 
 	# write high value to the timercmp just to be sure we don't
@@ -51,12 +51,13 @@ setup_timer_irq:
 
 irq_handler:
 	# save only the registers we use in this function
-	addi sp, sp, -24 # Allocate stack frame
-	sw ra, 20(sp)    # save return address to the stack
-	sw t0, 16(sp)    # save temporary
-	sw t1, 12(sp)    # save temporary
-	sw t2, 8(sp)    # save temporary
-	sw t3, 4(sp)    # save temporary
+	addi sp, sp, -28 # Allocate stack frame
+	sw ra, 24(sp)    # save return address to the stack
+	sw t0, 20(sp)    # save temporary
+	sw t1, 16(sp)    # save temporary
+	sw t2, 12(sp)    # save temporary
+	sw t3, 8(sp)     # save temporary
+	sw a0, 4(sp)     # save first argument to function
 
 	li t0, GPIO_CTRL_ADDR      # load base GPIO address
 	lw t1, GPIO_OUTPUT_VAL(t0) # load state
@@ -85,10 +86,14 @@ switchOnGreen:
 
 exit:
 	sw t2, GPIO_OUTPUT_VAL(t0)   # write new LED values to the right address
-	lw ra, 20(sp)   # load return address
-	lw t0, 16(sp)   # restore temporary
-	lw t1, 12(sp)   # restore temporary
-	lw t2, 8(sp)    # restore temporary
-	lw t3, 4(sp)    # restore temporary
-	addi sp, sp, 24 # deallocate stack frame
+	li a0, 200      # load the desired delay value (in ms) as the first arg to the function
+	jal delay       # call delay function to set new delay
+
+	lw ra, 24(sp)   # load return address
+	lw t0, 20(sp)   # restore temporary
+	lw t1, 16(sp)   # restore temporary
+	lw t2, 12(sp)   # restore temporary
+	lw t3, 8(sp)    # restore temporary
+	lw a0, 4(sp)    # restore first argument to function
+	addi sp, sp, 28 # deallocate stack frame
 	mret            # exit IRQ handler
-- 
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