gcn: trim noise off the per-port readout; add screenshots to each README

GameCube readout cleanups (visible in the new screenshot):

- Pak field now only renders for N64-style entries (N64 controller,
  N64 mouse, N64 mic) where the accessory slot is actually a thing.
  GCN / WaveBird / Wheel / Keyboard / GBA-attached ports drop the
  "Pak: None" filler.

- Keyboard line stripped to just "Style: Keyboard". The old "Pak:
  None / Rumble: Unavailable" trailers were nonsense for a keyboard
  -- it has neither an accessory slot nor a rumble motor.

- GBA-detected port now prints just "Boot: <state>" (Booted /
  BootIdle / BootFail). When state is BootFail it also surfaces the
  err code; on a successful boot or while still uploading the err
  field is suppressed. The Kawasedo-handshake echo-sample diagnostics
  (e=XXXXXXXX XXXXXXXX XXXXXXXX s=XX) that used to follow were
  first-time-bring-up debug noise -- removed. The supporting
  GBA_LastEcho / GBA_LastEchoStat / GBA_SnapEchoSamples accessors and
  their sample_* / last_echo* statics in gba.c/.h are dead-code
  removed in the same commit.

README screenshots:

- Each per-console README now embeds a screenshot at the top of
  "## What it tests": gcn/branding/screenshot.png (Dolphin output
  showing GCN / GBA-multiboot / Keyboard / spoofed-N64 across four
  ports), gba/branding/screenshot.png (the tester variant rendering
  in mGBA), pce/branding/screenshot.png (the main screen with
  yellow title + white data + cyan footer).

Author: RobertDaleSmith

gba/README.md

@@ -8,6 +8,10 @@ repo's GameCube/Wii host or run from a flash cart.
 
 ## What it tests
 
+<p align="center">
+  <img src="branding/screenshot.png" alt="GBA Joypad Tester tester-variant rendering: 'JOYPAD TESTER' header, 'GC Link: connected', 2-column live button list (A/B/Sel/Start/L on the left, Up/Down/Left/Right/R on the right), and a Raw hex of the joybus payload" width="480">
+</p>
+
 Each variant boots the same Doridian-style joybus controller loop and
 reports button state back to the host the moment a button changes. The
 two variants differ in what they render on the GBA screen:

gba/branding/screenshot.png

@@ -7,6 +7,10 @@ keyboard.
 
 ## What it tests
 
+<p align="center">
+  <img src="branding/screenshot.png" alt="GameCube Joypad Tester running in Dolphin showing GCN on Port 1, GBA-multiboot on Port 2, ASCII keyboard on Port 3, and N64 controller with Rumble Pak on Port 4" width="600">
+</p>
+
 All four SI ports rendered live, simultaneously, with no active-port toggle.
 Each port shows:
 

gcn/README.md

@@ -42,21 +42,6 @@ static u8 cmd_buf[8] ATTRIBUTE_ALIGN(32);
 static u8 resp_buf[8] ATTRIBUTE_ALIGN(32);
 static volatile u32 xfer_done_mask;
 
-// Diagnostic: last echo value read while waiting for payload handshake.
-static u32 last_echo[4];
-static u8  last_echo_stat[4];
-static u32 sample_echo[4][3];
-static u8  sample_stat[4][3];
-
-u32 GBA_LastEcho(int chan) { return last_echo[chan & 3]; }
-u8  GBA_LastEchoStat(int chan) { return last_echo_stat[chan & 3]; }
-void GBA_SnapEchoSamples(int chan, u32 echoes[3], u8 stats[3]) {
-  for (int i = 0; i < 3; i++) {
-    echoes[i] = sample_echo[chan & 3][i];
-    stats[i]  = sample_stat[chan & 3][i];
-  }
-}
-
 static void si_cb(s32 chan, u32 err) {
   (void)err;
   xfer_done_mask |= (1u << chan);
@@ -252,24 +237,11 @@ int GBA_BootEmbedded(int chan) {
   // Wait for payload's game-code echo.
   u32 expected = (u32)rom[0xAC] | ((u32)rom[0xAD] << 8) |
                  ((u32)rom[0xAE] << 16) | ((u32)rom[0xAF] << 24);
-  last_echo[chan & 3] = 0;
-  last_echo_stat[chan & 3] = 0;
-  for (int s = 0; s < 3; s++) {
-    sample_echo[chan & 3][s] = 0;
-    sample_stat[chan & 3][s] = 0;
-  }
-  int sample_idx = 0;
   bool got_echo = false;
   for (int p = 0; p < GBA_ECHO_ATTEMPTS; p++) {
     if (jb_read4(chan, r5)) {
       u32 v = (u32)r5[0] | ((u32)r5[1] << 8) | ((u32)r5[2] << 16) |
               ((u32)r5[3] << 24);
-      if (sample_idx < 3) {
-        sample_echo[chan & 3][sample_idx] = v;
-        sample_stat[chan & 3][sample_idx] = r5[4];
-        sample_idx++;
-      }
-      if (v != 0) { last_echo[chan & 3] = v; last_echo_stat[chan & 3] = r5[4]; }
       if (v == expected) { got_echo = true; break; }
     }
     busy_ms(GBA_ECHO_INTERVAL_MS);

gcn/branding/screenshot.png

@@ -15,16 +15,6 @@ bool GBA_Detect(int chan);
 // detection event.
 int GBA_BootEmbedded(int chan);
 
-// Diagnostic accessors — last value seen when waiting for the post-boot
-// game-code echo. Useful for distinguishing "BIOS rejected upload" (=
-// last encrypted word residue) from "payload running but unexpected
-// echo" (= 0x30303030 with byte-shift, or arbitrary garbage).
-u32 GBA_LastEcho(int chan);
-u8  GBA_LastEchoStat(int chan);
-// Capture of first 3 echo samples (post-multiboot reads), to spot
-// patterns. echoes[i] = value, stats[i] = JOYSTAT byte.
-void GBA_SnapEchoSamples(int chan, u32 echoes[3], u8 stats[3]);
-
 // After multiboot, read the GBA payload's input report.
 // Fills `out[2]` with [keys_lo, keys_hi]:
 //   out[0] bits 0..7 = A, B, Select, Start, Right, Left, Up, Down

gcn/ppc/gba.c

@@ -382,20 +382,35 @@ static void print_port(int p, const pad_snap_t *s) {
   printf("Port %d ", p + 1);
   SetFgColor(3, 2);
   printf("Style: %s ", format_style(s->style));
-  printf("Pak: %s ", format_pak(s->pak));
+  // Pak is N64-controller-specific (Memory / Rumble / Transfer / Bio /
+  // Snap Station). Standard GCN controllers, WaveBirds, the keyboard,
+  // the wheel, and an attached GBA have no Pak slot, so the field
+  // only renders for N64-style entries.
+  if (s->style == STYLE_N64 || s->style == STYLE_MOUSE ||
+      s->style == STYLE_MIC) {
+    printf("Pak: %s ", format_pak(s->pak));
+  } else {
+    printf("                  ");
+  }
   if (s->pak == PAK_BIO_SENSOR) {
     printf("BPM: %03d %-9s\n", s->bio_bpm,
            s->bio_pulsing ? "(Pulsing)" : "(Resting)");
   } else if (s->style == STYLE_GBA) {
-    const char *st = s->gba_state == 1 ? "Booted  "
+    const char *st = s->gba_state == 1 ? "Booted"
                    : s->gba_state == 2 ? "BootFail"
                                        : "BootIdle";
-    u32 e[3]; u8 st3[3];
-    GBA_SnapEchoSamples(p, e, st3);
-    printf("Boot:%s err%+d e=%08x %08x %08x s=%02x \n",
-           st, s->gba_boot_err,
-           (unsigned)e[0], (unsigned)e[1], (unsigned)e[2],
-           (unsigned)st3[0]);
+    // Only surface the boot error when the boot actually failed -- on
+    // a successful boot or while still uploading, the err code is
+    // noise. The Kawasedo handshake-echo samples that used to follow
+    // (e=... e=... e=... s=...) were only useful for first-time
+    // bring-up debugging and clutter the end-user readout, so they're
+    // gone too.
+    if (s->gba_state == 2) {
+      printf("Boot: %-8s err%+d                      \n",
+             st, s->gba_boot_err);
+    } else {
+      printf("Boot: %-32s\n", st);
+    }
   } else {
     printf("Rumble: %-11s\n",
            format_rumble(s->rumble_supported, s->rumble_active));
@@ -692,8 +707,10 @@ int main(int argc, char **argv) {
         SetFgColor(2, 2);
         printf("Port %d ", i + 1);
         SetFgColor(3, 2);
-        printf("Style: %s Pak: None         Rumble: Unavailable\n",
-               format_style(STYLE_KEYBOARD));
+        // Keyboard has no Pak slot, no rumble, no analog axes -- drop
+        // the noise and just label the port. Trailing spaces overwrite
+        // any leftover text from a previous frame's mode.
+        printf("Style: %s%-46s\n", format_style(STYLE_KEYBOARD), "");
         SetFgColor(7, 2);
         const char *k0 = gc_key_label(r[4]);
         const char *k1 = gc_key_label(r[5]);

gcn/ppc/gba.h

@@ -7,6 +7,10 @@ Engine mouse.
 
 ## What it tests
 
+<p align="center">
+  <img src="branding/screenshot.png" alt="PC Engine Joypad Tester main screen: yellow 'Joypad Tester - PC Engine' title, white live P1..P5 + Mouse + abs x/y readouts in two columns, cyan 'Press I button or right-click to toggle mouse mode.' footer" width="600">
+</p>
+
 Each of the five potential joypad slots (single pad on port 0, or up to
 five through a PCE multitap) is shown live as the raw 16-bit joybus
 read. The mouse, if present, gets a separate decoded readout with