From fa41d47e1f998312d6f27a7463cc5664e0f7d376 Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Mon, 9 Jan 2023 19:41:02 -0800
Subject: [PATCH] make the smpc intback interrupt do something

---
 main.c | 22 +++++++++++++++++++++-
 smpc.h | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/main.c b/main.c
index 402a745..8d36ec0 100644
--- a/main.c
+++ b/main.c
@@ -44,7 +44,7 @@ void oci_int(void)
 
   smpc.reg.IREG0 = INTBACK__IREG0__STATUS_DISABLE;
   smpc.reg.IREG1 = ( INTBACK__IREG1__PERIPHERAL_DATA_ENABLE
-                   | INTBACK__IREG1__PORT2_15BYTE
+                   | INTBACK__IREG1__PORT2_0BYTE
                    | INTBACK__IREG1__PORT1_15BYTE
                    );
   smpc.reg.IREG2 = INTBACK__IREG2__MAGIC;
@@ -60,6 +60,26 @@ void smpc_int(void)
 {
   scu.reg.IST &= ~(IST__SMPC);
 
+  if (smpc.reg.SR & SR__PDL) {
+    // to get all controller data, one should check SR__NPE and send CONTINUE
+    // requests as needed
+
+    // assuming SR__PDL is set and SR__P1MD is not 0-byte-mode:
+    //   smpc.reg.OREG0 (port 1 status)
+    //   smpc.reg.OREG1 (peripheral 1 data[0] {type,size})
+    //   smpc.reg.OREG2 (peripheral 1 data[1])
+
+    if ((smpc.reg.OREG2 & DIGITAL__1__C) == 0) {
+      // if C is pressed, swap the color palette
+      vdp2.cram.u16[1] = (0x31 << 10); // blue
+      vdp2.cram.u16[2] = (0x31 << 5);  // green
+    } else {
+      // if C is not pressed, restore the original palette
+      vdp2.cram.u16[1] = (0x31 << 5);  // green
+      vdp2.cram.u16[2] = (0x31 << 10); // blue
+    }
+  }
+
   smpc.reg.IREG0 = INTBACK__IREG0__BREAK;
 }
 
diff --git a/smpc.h b/smpc.h
index 6bdf86d..e80105f 100644
--- a/smpc.h
+++ b/smpc.h
@@ -180,3 +180,37 @@ enum intback_ireg_bit {
 
   INTBACK__IREG2__MAGIC = (0xF0),
 };
+
+enum sr_bit {
+  SR__PDL = (1 << 6),
+  SR__NPE = (1 << 5),
+  SR__RESB = (1 << 4),
+  SR__P2MD1 = (1 << 3),
+  SR__P2MD0 = (1 << 2),
+  SR__P1MD1 = (1 << 1),
+  SR__P1MD0 = (1 << 0),
+#define SR__P2MD__15BYTE(sr) (((sr & 0b00001100)) == (0b00 << 2))
+#define SR__P2MD__255BYTE(sr) (((sr & 0b00001100)) == (0b01 << 2))
+#define SR__P2MD__0BYTE(sr) (((sr & 0b00001100)) == (0b11 << 2))
+
+#define SR__P1MD__15BYTE(sr) (((sr & 0b00000011)) == (0b00 << 0))
+#define SR__P1MD__255BYTE(sr) (((sr & 0b00000011)) == (0b01 << 0))
+#define SR__P1MD__0BYTE(sr) (((sr & 0b00000011)) == (0b11 << 0))
+};
+
+enum digital_bit {
+  DIGITAL__1__RIGHT = (1 << 7),
+  DIGITAL__1__LEFT = (1 << 6),
+  DIGITAL__1__DOWN = (1 << 5),
+  DIGITAL__1__UP = (1 << 4),
+  DIGITAL__1__START = (1 << 3),
+  DIGITAL__1__A = (1 << 2),
+  DIGITAL__1__C = (1 << 1),
+  DIGITAL__1__B = (1 << 0),
+
+  DIGITAL__2__R = (1 << 7),
+  DIGITAL__2__X = (1 << 6),
+  DIGITAL__2__Y = (1 << 5),
+  DIGITAL__2__Z = (1 << 4),
+  DIGITAL__2__L = (1 << 3),
+};