Add second sync bit to flag errors back to the Sega

Also split firmware speed tests out into their own file

hardware/firmware/fast-gpio.h

@@ -29,8 +29,10 @@
 #define SRAM_PIN__DATA_CLOCK    22
 #define SRAM_PIN__DATA_WRITE    14
 
-#define SYNC_PIN__READY         10
-#define SYNC_PIN__CLEAR         11
+#define SYNC_PIN__CMD_READY     10
+#define SYNC_PIN__CMD_CLEAR     11
+#define SYNC_PIN__ERR_FLAGGED   27
+#define SYNC_PIN__ERR_SET       26
 
 #define REG_PIN__A0              8
 #define REG_PIN__A1              9
@@ -64,8 +66,10 @@
 #define SRAM_PIN__DATA_CLOCK     0
 #define SRAM_PIN__DATA_WRITE     0
 
-#define SYNC_PIN__READY          0
-#define SYNC_PIN__CLEAR          0
+#define SYNC_PIN__CMD_READY      0
+#define SYNC_PIN__CMD_CLEAR      0
+#define SYNC_PIN__ERR_FLAGGED    0
+#define SYNC_PIN__ERR_SET        0
 
 #define REG_PIN__A0              0
 #define REG_PIN__A1              0

hardware/firmware/firmware.ino

@@ -15,91 +15,25 @@
 #include "http.h"
 #include "internet.h"
 #include "registers.h"
+#include "speed-tests.h"
 #include "sram.h"
 
-#define SERVER "storage.googleapis.com"
-#define PATH   "/sega-kinetoscope/canned-videos/NEVER_GONNA_GIVE_YOU_UP.segavideo"
-
 // An actual MAC address assigned to me with my ethernet board.
 // Don't put two of these devices on the same network, y'all.
 uint8_t MAC_ADDR[] = { 0x98, 0x76, 0xB6, 0x12, 0xD4, 0x9E };
 
-// ~3s worth of audio+video data with headers and worst-case padding.
-#define ABOUT_3S_VIDEO_AUDIO_BYTES 901932
-
-// A safe buffer size for these tests.
-#define BUFFER_SIZE 100 * 1024
-
-static long test_sram_speed(uint8_t* buffer, int bytes) {
-  // 100kB: ~83ms
-  // 1MB: ~830ms
-  // 3s video+audio: ~731ms
-  long start = millis();
-  sram_start_bank(0);
-  sram_write(buffer, bytes);
-  sram_flush();
-  long end = millis();
-  return end - start;
-}
-
-static long test_sync_token_read_speed() {
-  // ~114 ns per read
-  long start = millis();
-  int count = 0;
-  for (int i = 0; i < 1000000; ++i) {
-    count += is_sync_token_set();
-  }
-  long end = millis();
-  return end - start;
-}
-
-static long test_sync_token_clear_speed() {
-  // ~114 ns per clear
-  long start = millis();
-  for (int i = 0; i < 1000000; ++i) {
-    clear_sync_token();
-  }
-  long end = millis();
-  return end - start;
-}
-
-static long test_register_read_speed() {
-  // ~228 ns per read
-  int count = 0;
-  long start = millis();
-  for (int i = 0; i < 1000000; ++i) {
-    count += read_register(i & 3);
-  }
-  long end = millis();
-  return end - start;
-}
-
-static long test_download_speed(int first_byte, int total_size) {
-  // 2.5Mbps minimum required
-  // ~2.7Mbps with initial HTTP connection overhead
-  // ~3.0Mbps on subsequent requests @902kB
-  long start = millis();
-  sram_start_bank(0);
-  int bytes_read = http_fetch(SERVER, /* default port */ 0, PATH,
-                              first_byte, total_size,
-                              sram_write);
-  sram_flush();
-  long end = millis();
-  return end - start;
-}
-
-uint8_t* buffer;
-
 void setup() {
   Serial.begin(115200);
   while (!Serial) { delay(10); }  // Wait for serial port to connect
 
   // Delay startup so we can have the serial monitor attached.
   delay(1000);
-  Serial.println("Hello, world!\n");
+  Serial.println("Kinetoscope boot!\n");
 
   sram_init();
   registers_init();
+  pinMode(LED_BUILTIN, OUTPUT);
+  digitalWrite(LED_BUILTIN, HIGH);
 
   // Prefer wired, fall back to WiFi if configured.
   Client* client = internet_init_wired(MAC_ADDR);
@@ -128,49 +62,9 @@ void setup() {
   }
 
   http_init(client);
-
-  pinMode(LED_BUILTIN, OUTPUT);
-
-  buffer = (uint8_t*)malloc(BUFFER_SIZE);
-  if (!buffer) {
-    Serial.println("Failed to allocate test buffer!");
-    while (true) { delay(1000); }
-  }
-
-  Serial.println("\n");
 }
 
 void loop() {
-  long ms;
-
-  ms = test_sync_token_read_speed();
-  Serial.print(ms);
-  Serial.println(" ns avg per sync token read.");  // 1Mx reads, ms => ns
-
-  ms = test_sync_token_clear_speed();
-  Serial.print(ms);
-  Serial.println(" ns avg per sync token clear.");  // 1Mx reads, ms => ns
-
-  ms = test_register_read_speed();
-  Serial.print(ms);
-  Serial.println(" ns avg per register read.");  // 1Mx reads, ms => ns
-
-  ms = test_sram_speed(buffer, BUFFER_SIZE);
-  Serial.print(ms);
-  Serial.print(" ms to write ");
-  Serial.print(BUFFER_SIZE);
-  Serial.println(" bytes to SRAM");
-
-  for (int i = 0; i < 10; i++) {
-    ms = test_download_speed(/* first_byte= */ i, ABOUT_3S_VIDEO_AUDIO_BYTES);
-    float bits = ABOUT_3S_VIDEO_AUDIO_BYTES * 8.0;
-    float seconds = ms / 1000.0;
-    float mbps = bits / seconds / 1024.0 / 1024.0;
-    Serial.print(ms);
-    Serial.print(" ms to stream ~3s video to SRAM (");
-    Serial.print(mbps);
-    Serial.println(" Mbps vs 2.50 Mbps minimum)");
-  }
-
+  run_tests();
   while (true) { delay(1000); }
 }

hardware/firmware/registers.cc

@@ -21,37 +21,48 @@
 
 void registers_init() {
   // Set modes on register and sync pins.
-  pinMode(REG_PIN__D0, INPUT);
-  pinMode(REG_PIN__D1, INPUT);
-  pinMode(REG_PIN__D2, INPUT);
-  pinMode(REG_PIN__D3, INPUT);
-  pinMode(REG_PIN__D4, INPUT);
-  pinMode(REG_PIN__D5, INPUT);
-  pinMode(REG_PIN__D6, INPUT);
-  pinMode(REG_PIN__D7, INPUT);
+  pinMode(REG_PIN__D0, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D1, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D2, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D3, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D4, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D5, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D6, INPUT_PULLDOWN);
+  pinMode(REG_PIN__D7, INPUT_PULLDOWN);
 
   pinMode(REG_PIN__A0, OUTPUT);
   pinMode(REG_PIN__A1, OUTPUT);
 
-  pinMode(SYNC_PIN__READY, INPUT);
-  pinMode(SYNC_PIN__CLEAR, OUTPUT);
+  pinMode(SYNC_PIN__CMD_READY, INPUT_PULLDOWN);
+  pinMode(SYNC_PIN__CMD_CLEAR, OUTPUT);
+  pinMode(SYNC_PIN__ERR_SET, OUTPUT);
+  pinMode(SYNC_PIN__ERR_FLAGGED, INPUT_PULLDOWN);
 
   // Disable active-low signals by default (setting them high).
-  FAST_SET(SYNC_PIN__CLEAR);
+  FAST_SET(SYNC_PIN__CMD_CLEAR);
+  FAST_SET(SYNC_PIN__ERR_SET);
 
   // Set other outputs low by default.
   FAST_CLEAR(REG_PIN__A0);
   FAST_CLEAR(REG_PIN__A1);
 
-  clear_sync_token();
+  clear_cmd();
 }
 
-int is_sync_token_set() {
-  return FAST_GET(SYNC_PIN__READY);
+int is_cmd_set() {
+  return FAST_GET(SYNC_PIN__CMD_READY);
 }
 
-void clear_sync_token() {
-  FAST_PULSE_ACTIVE_LOW(SYNC_PIN__CLEAR);
+void clear_cmd() {
+  FAST_PULSE_ACTIVE_LOW(SYNC_PIN__CMD_CLEAR);
+}
+
+void flag_error() {
+  FAST_PULSE_ACTIVE_LOW(SYNC_PIN__ERR_SET);
+}
+
+int is_err_flagged() {
+  return FAST_GET(SYNC_PIN__ERR_FLAGGED);
 }
 
 uint8_t read_register(int register_address) {

hardware/firmware/registers.h

@@ -19,11 +19,29 @@
 
 #include <inttypes.h>
 
+// These are the sega address bits A2 and A1.  There is no A0 signal from the
+// sega, since it has a 16-bit data bus.
+#define KINETOSCOPE_REG_CMD      0   // Sega's 0xA13000
+#define KINETOSCOPE_REG_ARG      1   // Sega's 0xA13002
+// These exist in hardware but aren't used at the moment.
+#define KINETOSCOPE_REG_UNUSED_2 2
+#define KINETOSCOPE_REG_UNUSED_3 3
+
+#define KINETOSCOPE_CMD_ECHO        0x00  // Writes arg to SRAM
+#define KINETOSCOPE_CMD_LIST_VIDEOS 0x01  // Writes video list to SRAM
+#define KINETOSCOPE_CMD_START_VIDEO 0x02  // Begins streaming to SRAM
+#define KINETOSCOPE_CMD_STOP_VIDEO  0x03  // Stops streaming
+#define KINETOSCOPE_CMD_FLIP_REGION 0x04  // Switch SRAM banks for streaming
+
 void registers_init();
 
-int is_sync_token_set();
+int is_cmd_set();
+
+void clear_cmd();
+
+void flag_error();
 
-void clear_sync_token();
+int is_err_flagged();
 
 uint8_t read_register(int register_address);
 

hardware/firmware/speed-tests.cc

@@ -0,0 +1,124 @@
+// Kinetoscope: A Sega Genesis Video Player
+//
+// Copyright (c) 2024 Joey Parrish
+//
+// See MIT License in LICENSE.txt
+
+// Microcontroller function speed tests.
+
+#include <Arduino.h>
+#include <HardwareSerial.h>
+
+#include "http.h"
+#include "registers.h"
+#include "sram.h"
+
+#define SERVER "storage.googleapis.com"
+#define PATH   "/sega-kinetoscope/canned-videos/NEVER_GONNA_GIVE_YOU_UP.segavideo"
+
+// ~3s worth of audio+video data with headers and worst-case padding.
+#define ABOUT_3S_VIDEO_AUDIO_BYTES 901932
+
+// A safe buffer size for these tests.
+#define BUFFER_SIZE 100 * 1024
+
+static long test_sram_speed(uint8_t* buffer, int bytes) {
+  // 100kB: ~83ms
+  // 1MB: ~830ms
+  // 3s video+audio: ~731ms
+  long start = millis();
+  sram_start_bank(0);
+  sram_write(buffer, bytes);
+  sram_flush();
+  long end = millis();
+  return end - start;
+}
+
+static long test_sync_token_read_speed() {
+  // ~114 ns per read
+  long start = millis();
+  int count = 0;
+  for (int i = 0; i < 1000000; ++i) {
+    count += is_cmd_set();
+  }
+  long end = millis();
+  return end - start;
+}
+
+static long test_sync_token_clear_speed() {
+  // ~114 ns per clear
+  long start = millis();
+  for (int i = 0; i < 1000000; ++i) {
+    clear_cmd();
+  }
+  long end = millis();
+  return end - start;
+}
+
+static long test_register_read_speed() {
+  // ~228 ns per read
+  int count = 0;
+  long start = millis();
+  for (int i = 0; i < 1000000; ++i) {
+    count += read_register(i & 3);
+  }
+  long end = millis();
+  return end - start;
+}
+
+static long test_download_speed(int first_byte, int total_size) {
+  // 2.5Mbps minimum required
+  // ~2.7Mbps with initial HTTP connection overhead
+  // ~3.0Mbps on subsequent requests @902kB
+  long start = millis();
+  sram_start_bank(0);
+  int bytes_read = http_fetch(SERVER, /* default port */ 0, PATH,
+                              first_byte, total_size,
+                              sram_write);
+  sram_flush();
+  long end = millis();
+  return end - start;
+}
+
+void run_tests() {
+  long ms;
+
+  uint8_t* buffer = NULL;
+  buffer = (uint8_t*)malloc(BUFFER_SIZE);
+  if (!buffer) {
+    Serial.println("Failed to allocate buffer!");
+    while (true) { delay(1000); }
+  }
+
+  ms = test_sync_token_read_speed();
+  Serial.print(ms);
+  Serial.println(" ns avg per sync token read.");  // 1Mx reads, ms => ns
+
+  ms = test_sync_token_clear_speed();
+  Serial.print(ms);
+  Serial.println(" ns avg per sync token clear.");  // 1Mx reads, ms => ns
+
+  ms = test_register_read_speed();
+  Serial.print(ms);
+  Serial.println(" ns avg per register read.");  // 1Mx reads, ms => ns
+
+  ms = test_sram_speed(buffer, BUFFER_SIZE);
+  Serial.print(ms);
+  Serial.print(" ms to write ");
+  Serial.print(buffer_size);
+  Serial.println(" bytes to SRAM");
+
+  for (int i = 0; i < 10; i++) {
+    ms = test_download_speed(/* first_byte= */ i, ABOUT_3S_VIDEO_AUDIO_BYTES);
+    float bits = ABOUT_3S_VIDEO_AUDIO_BYTES * 8.0;
+    float seconds = ms / 1000.0;
+    float mbps = bits / seconds / 1024.0 / 1024.0;
+    Serial.print(ms);
+    Serial.print(" ms to stream ~3s video to SRAM (");
+    Serial.print(mbps);
+    Serial.println(" Mbps vs 2.50 Mbps minimum)");
+  }
+
+  Serial.println("\n");
+  free(buffer);
+}