[target][pico] switch the uart config to target driven

Uses the target/debugconfig.h file pattern laid down before,
which is a bit long in the tooth but for the moment still helps
us separate target from platform.

platform/rp20xx/debug.c

@@ -6,20 +6,22 @@
 
 #include <platform/debug.h>
 
+#include <target/debugconfig.h>
+
 #include <hardware/uart.h>
 
 #include <stdio.h>
 
 void platform_dputc(char c) {
     if (c == '\n')
-        uart_putc(uart0, '\r');
-    uart_putc(uart0, c);
+        uart_putc(DEBUG_UART, '\r');
+    uart_putc(DEBUG_UART, c);
 }
 
 int platform_dgetc(char *c, bool wait) {
-    if (!wait && !uart_is_readable(uart0))
+    if (!wait && !uart_is_readable(DEBUG_UART))
         return -1;
-    *c = uart_getc(uart0);
+    *c = uart_getc(DEBUG_UART);
     return 0;
 }
 

platform/rp20xx/init.c

@@ -6,6 +6,7 @@
 
 #include <platform.h>
 #include <arch/arm/cm.h>
+#include <target/debugconfig.h>
 
 #include <hardware/clocks.h>
 #include <hardware/gpio.h>
@@ -15,16 +16,22 @@
 extern void* vectab;
 
 void platform_early_init(void) {
+    // initialize the clock tree.
+    // gets clock values from defines in SDK at
+    // external/platform/pico/rp2040/hardware_regs/include/hardware/platform_defs.h
     clocks_init();
 
+    // start the systick timer
+    arm_cm_systick_init(125000000);
+
+    // unreset everything
     unreset_block_wait(RESETS_RESET_BITS);
 
-    uart_init(uart0, 1000000);
-    gpio_set_function(0, GPIO_FUNC_UART);
-    gpio_set_function(1, GPIO_FUNC_UART);
-    uart_puts(uart0, "Hello World!\n");
-
-    arm_cm_systick_init(133000000);
+    // target defines drive how we configure the debug uart
+    uart_init(DEBUG_UART, 115200);
+    gpio_set_function(DEBUG_UART_GPIOA, GPIO_FUNC_UART);
+    gpio_set_function(DEBUG_UART_GPIOB, GPIO_FUNC_UART);
+    uart_puts(DEBUG_UART, "Hello World!\n");
 }
 
 void platform_init(void) {
@@ -32,5 +39,5 @@ void platform_init(void) {
 
 
 bool running_on_fpga(void) {
-	return false;
+    return false;
 }

target/pico/include/target/debugconfig.h

@@ -1,3 +1,14 @@
+// Copyright (c) 2020 Brian Swetland
+//
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT
+
 #pragma once
 
-#define DEBUG_UART 0
+#include <hardware/uart.h>
+
+// define how this target will map the debug uart to hardware and pins
+#define DEBUG_UART uart0
+#define DEBUG_UART_GPIOA 0
+#define DEBUG_UART_GPIOB 1

target/pico/target.c

@@ -5,9 +5,9 @@
 // https://opensource.org/licenses/MIT
 
 #include <target.h>
+#include <target/debugconfig.h>
 #include <platform/gpio.h>
 
-
 void target_early_init(void) {
 }