From e0648c1048189fb32ec48cc8d1c124a5e0d8f402 Mon Sep 17 00:00:00 2001
From: Oliver Schmidt <ol.sc@web.de>
Date: Sun, 11 Sep 2022 23:15:27 +0200
Subject: [PATCH] Updated from https://github.com/a2retrosystems/A2retroNET

At this point, nothing at all is done on an A2 reset. This can likely be improved. However, Apple2-IO-RPi doesn't seem to handle A2 reset exactly gracefully anyhow.

In general, it seems desirable to introduce some simple framing protocol - like SLIP - that allows to recover from an A2 reset in the middle of an Apple2-IO-RPi command execution.

Such a framing protocol would allow to introduce different frame types. One frame type could then be an A2 reset frame sent by the A2retroNET firmware.
---
 RaspberryPiPico/board.c | 18 +++++++-----------
 RaspberryPiPico/bus.pio |  2 +-
 RaspberryPiPico/main.c  | 10 ++++++++++
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/RaspberryPiPico/board.c b/RaspberryPiPico/board.c
index 953f29d..cf62246 100644
--- a/RaspberryPiPico/board.c
+++ b/RaspberryPiPico/board.c
@@ -32,9 +32,9 @@ SOFTWARE.
 
 extern const __attribute__((aligned(4))) uint8_t firmware[];
 
-static uint32_t __not_in_flash("page") page;
+static uint32_t page;
 
-void __not_in_flash_func(board)(void) {
+void __time_critical_func(board)(void) {
     for (uint gpio = gpio_addr; gpio < gpio_addr + size_addr; gpio++) {
         gpio_init(gpio);
         gpio_set_pulls(gpio, false, false);  // floating
@@ -46,13 +46,7 @@ void __not_in_flash_func(board)(void) {
     }
 
     gpio_init(gpio_enbl);
-    gpio_pull_up(gpio_enbl);
-
-    gpio_init(gpio_irq);
-    gpio_pull_up(gpio_irq);
-
-    gpio_init(gpio_nmi);
-    gpio_pull_up(gpio_nmi);
+    gpio_set_pulls(gpio_enbl, false, false);  // floating
 
     uint offset;
 
@@ -65,6 +59,8 @@ void __not_in_flash_func(board)(void) {
     offset = pio_add_program(pio0, &read_program);
     read_program_init(offset);
 
+    page = 0;
+
     while (true) {
         uint32_t enbl = pio_sm_get_blocking(pio0, sm_enbl);
         uint32_t addr = enbl & 0x0FFF;
@@ -73,7 +69,7 @@ void __not_in_flash_func(board)(void) {
         uint32_t read = enbl & 0x1000;  // R/W
 
         if (read) {
-            if (!io) {
+            if (!io) {  // DEVSEL
                 switch (addr & 0x7) {
                     case 0x3:
                         pio_sm_put(pio0, sm_read, !multicore_fifo_rvalid() << 7 |
@@ -90,7 +86,7 @@ void __not_in_flash_func(board)(void) {
             }
         } else {
             uint32_t data = pio_sm_get_blocking(pio0, sm_write);
-            if (!io) {
+            if (!io) {  // DEVSEL
                 switch (addr & 0x7) {
                     case 0x5:
                         sio_hw->fifo_wr = data;
diff --git a/RaspberryPiPico/bus.pio b/RaspberryPiPico/bus.pio
index 9098e56..d708a8e 100644
--- a/RaspberryPiPico/bus.pio
+++ b/RaspberryPiPico/bus.pio
@@ -33,7 +33,7 @@ SOFTWARE.
 .define public gpio_data    15  //  8 pins
 .define public gpio_enbl    26  // DEVSEL | IOSEL | IOSTRB
 .define public gpio_irq     27
-.define public gpio_nmi     28
+.define public gpio_res     28
 
 .define public size_addr    13  // incl. R/W
 .define public size_data    8
diff --git a/RaspberryPiPico/main.c b/RaspberryPiPico/main.c
index df27a45..d0f8efc 100644
--- a/RaspberryPiPico/main.c
+++ b/RaspberryPiPico/main.c
@@ -32,6 +32,7 @@ SOFTWARE.
 #include "pico/cyw43_arch.h"
 #endif
 
+#include "bus.pio.h"
 #include "board.h"
 
 #ifdef TRACE
@@ -48,6 +49,9 @@ void uart_printf(uart_inst_t *uart, const char *format, ...) {
 }
 #endif
 
+void res_callback(uint gpio, uint32_t events) {
+}
+
 void main(void) {
     multicore_launch_core1(board);
 
@@ -58,6 +62,12 @@ void main(void) {
     gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
 #endif
 
+    gpio_init(gpio_irq);
+    gpio_pull_up(gpio_irq);
+
+    gpio_init(gpio_res);
+    gpio_set_irq_enabled_with_callback(gpio_res, GPIO_IRQ_EDGE_RISE, true, &res_callback);
+
     stdio_init_all();
     stdio_set_translate_crlf(&stdio_usb, false);