1 files changed, 23 insertions, 0 deletions
diff --git a/setup/gpio.s b/setup/gpio.s
new file mode 100644
index 0000000..32e2c37
--- /dev/null
+++ b/setup/gpio.s
@@ -0,0 +1,23 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.equ RESETS_BASE, 0x4000c000
+.equ RESET_OFST,      0x0
+.equ RESET_DONE_OFST, 0x8
+
+.equ ATOMIC_CLEAR,    0x3000
+
+.type setup_gpio, %function
+.global setup_gpio
+
+setup_gpio:
+  ldr r1, =(RESETS_BASE + ATOMIC_CLEAR)
+  movs r0, 0b1 << 5 // IO_BANK0
+  str r0, [r1, RESET_OFST]
+  ldr r1, =RESETS_BASE
+1:
+  ldr r2, [r1, RESET_DONE_OFST]
+  tst r2, r0
+  beq 1b
+  bx lr