rp2040

commit 4db5a73bf8811b1e44c1cc5ef977f525f5723afa
parent 0910282b64f2b903349da9cfb91f0e7725115df8
Author: Matsuda Kenji <info@mtkn.jp>
Date:   Wed, 13 Aug 2025 07:47:59 +0900

enable sio

Diffstat:
M
ex3_spi/main.s
 | 
29
+++++++++++++++++++++++++----

1 file changed, 25 insertions(+), 4 deletions(-)
diff --git a/ex3_spi/main.s b/ex3_spi/main.s
@@ -68,11 +68,24 @@ unreset_chk:
 
 	// set gpio functions
 	ldr r3, io_bank0_base
+	// set pins 0 and 1 for uart
 	mov r0, #2 // uart0
 	mov r1, #0x4
 	str r0, [r3, r1] // IO_BANK0: GPIO0_CTRL
 	mov r1, #0xc
 	str r0, [r3, r1] // IO_BANK0: GPIO1_CTRL
+	// set pins 24 and 25 to SIO for led blink.
+	mov r0, #5 // sio
+	mov r1, #0xc4
+	str r0, [r3, r1] // IO_BANK0: GPIO24_CTRL
+	mov r1, #0xcc
+	str r0, [r3, r1] // IO_BANK0: GPIO24_CTRL
+
+	// enable sio output
+	ldr r3, sio_base
+	mov r0, #0b11
+	lsl r0, r0, #24
+	str r0, [r3, #0x24] // SIO: GPIO_OE
 
 	// setup xosc
 	ldr r3, xosc_base
@@ -150,11 +163,10 @@ wait_vco:
 	// set fifo level to 0
 	mov r2, #0
 	str r2, [r1, #0x34] // UART: UARTIFLS
-	bl delay
-	ldr r0, [r1, #0x3c] // UART: UARTRIS
-	bl printh
 
 loop:
+	bl bled0
+	bl bled1
 	wfe
 	b loop
 
@@ -183,6 +195,8 @@ alpha:
 	bge printh_loop
 	pop {r4, r5, r6, r7, pc}
 
+	// putbyte sends a byte specified by r0 to uart0.
+	// It busy-waits for the buffer to become available.
 putbyte:
 	ldr r3, uart0_base
 	mov r1, #1
@@ -196,6 +210,8 @@ txff:
 	str r0, [r3, #0] // UART: UARTDR
 	bx lr
 
+	// getbyte reads a byte from uart0 and returns it on r0
+	// It busy-waits for a data.
 getbyte:
 	ldr r3, uart0_base
 	mov r1, #1
@@ -213,7 +229,7 @@ rxfe:
 // can be used anywhare without pushing and popping
 // registers.
 
-	// Print register content with 2 leds, lsb first.
+	// pled prints register content with 2 leds on the pins 24 and 25, lsb first.
 pled:
 	push {r0, r1, r2, r3, r4, r5, r6, lr}
 	mov r4, r0
@@ -232,6 +248,7 @@ pled1:
 	bne pled_loop
 	pop {r0, r1, r2, r3, r4, r5, r6, pc}
 
+	// bled0 blinks the led on the pin 24 once.
 bled0:
 	push {r0, r1, r2, r3, lr}
 	mov r0, #1
@@ -239,6 +256,7 @@ bled0:
 	bl bled
 	pop {r0, r1, r2, r3, pc}
 
+	// bled1 blinks the led on the pin 25 once.
 bled1:
 	push {r0, r1, r2, r3, lr}
 	mov r0, #1
@@ -246,6 +264,7 @@ bled1:
 	bl bled
 	pop {r0, r1, r2, r3, pc}
 
+	// bled blinks the led on the pin specified by r0 once.
 bled:
 	push {r0, r1, r2, r3, r4, r5, lr}
 	ldr r4, sio_base
@@ -256,6 +275,7 @@ bled:
 	bl delay
 	pop {r0, r1, r2, r3, r4, r5, pc}
 	
+	// delay delays for a moment by counting down a register.
 delay:
 	push {r0}
 	mov r0, #1
@@ -266,6 +286,7 @@ delay_loop:
 	pop {r0}
 	bx lr
 
+	// uart_interrupt_handler echos the data arrived at uart0
 uart_interrupt_handler:
 	push {lr}
 	bl getbyte