1 files changed, 94 insertions, 0 deletions
diff --git a/octedit/setup.s b/octedit/setup.s
new file mode 100644
index 0000000..378b54e
--- /dev/null
+++ b/octedit/setup.s
@@ -0,0 +1,94 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.equ XOSC_BASE, 0x40024000
+.equ CTRL_OFST, 0x0
+.equ STATUS_OFST, 0x4
+.equ STARTUP_OFST, 0xc
+
+.equ CLOCKS_BASE, 0x40008000
+.equ CLK_REF_CTRL_OFST,  0x30
+.equ CLK_SYS_CTRL_OFST,  0x3c
+.equ CLK_PERI_CTRL_OFST, 0x48
+
+.equ RESETS_BASE, 0x4000c000
+.equ RESET_OFST,      0x0
+.equ RESET_DONE_OFST, 0x8
+
+.equ IO_BANK0_BASE, 0x40014000
+.equ GPIO0_CTRL_OFST, 0x04
+.equ GPIO1_CTRL_OFST, 0x0c
+
+.equ UART0_BASE, 0x40034000
+.equ UARTDR_OFST,     0x00
+.equ UARTFR_OFST,     0x18
+.equ UARTIBRD_OFST,   0x24
+.equ UARTFBRD_OFST,   0x28
+.equ UARTLCR_H_OFST,  0x2c
+.equ UARTCR_OFST,     0x30
+
+.equ ATOMIC_SET,    0x2000
+.equ ATOMIC_CLEAR,  0x3000
+
+.type setup, %function
+.global setup
+
+setup:
+
+  // XOSC
+  ldr r1, =XOSC_BASE
+  movs r0, 47 // startup delay for 12Mhz crystal
+  str r0, [r1, STARTUP_OFST]
+  ldr r0, =0x00fabaa0 // enable
+  str r0, [r1, CTRL_OFST]
+1:
+  ldr r0, [r1, STATUS_OFST]
+  lsrs r0, 31 // stable bit
+  beq 1b
+
+  // Clocks
+  ldr r1, =CLOCKS_BASE
+  // Reference clock
+  movs r0, 0x2 // src = xosc
+  str r0, [r1, CLK_REF_CTRL_OFST]
+  // System clock
+  movs r0, 0x0 // src = clk_ref
+  str r0, [r1, CLK_SYS_CTRL_OFST]
+  // Peripheral clock
+  movs r0, 1 // set enable
+  lsls r0, 11
+  adds r0, 0x4 << 5 // src = xosc
+  str r0, [r1, CLK_PERI_CTRL_OFST]
+
+  // Deassert resets for GPIO and UART
+  movs r0, 0b1 << 5 // IO_BANK0 (bit 5)
+  movs r1, 0b1 // UART0 (bit 22)
+  lsls r1, 22
+  orrs r0, r1
+  ldr r1, =(RESETS_BASE + ATOMIC_CLEAR)
+  str r0, [r1, RESET_OFST]
+  ldr r1, =RESETS_BASE
+1:
+  ldr r2, [r1, RESET_DONE_OFST]
+  tst r2, r0
+  beq 1b
+
+  // Configure and enable UART
+  ldr r1, =UART0_BASE
+  movs r0, 6
+  str r0, [r1, UARTIBRD_OFST]
+  movs r0, 33
+  str r0, [r1, UARTFBRD_OFST]
+  movs r0, 0b111 << 4 // 0b11 = word len 8 bits, 0b1 = FIFO enabled
+  str r0, [r1, UARTLCR_H_OFST]
+  ldr r1, =(UART0_BASE + ATOMIC_SET)
+  movs r0, 0b1 // UART enable
+  str r0, [r1, UARTCR_OFST]
+  // Configure GPIO 0 and 1 as TX and RX
+  ldr r1, =IO_BANK0_BASE
+  movs r0, 2 // UART function
+  str r0, [r1, GPIO0_CTRL_OFST]
+  str r0, [r1, GPIO1_CTRL_OFST]
+
+  b octedit