Add support for custom peripherals

CMakeLists.txt

@@ -18,12 +18,14 @@ set(CORE_SRCS
     src/int.c
     src/keyboard.c
     src/main.c
+    src/charmon.c
     src/serial.c
     src/sio2.c
     src/speaker.c
     src/time.c
     src/timer.c
     src/tokenizer.c
+    src/ubus.c
     src/upd8255.c
     src/video.c
     src/ram/auxram.c

conf/ceda-cemu.ini

@@ -15,6 +15,10 @@
 # See: https://github.com/GLGPrograms/ceda-img
 cge_installed = true
 
+# Character Device Monitor, write-only
+# Virtual peripheral to log via stdout on the emulator
+charmon_installed = false
+
 [path]
 
 # Custom path for BIOS ROM, else default is used

src/bus.c

@@ -10,6 +10,7 @@
 #include "sio2.h"
 #include "speaker.h"
 #include "timer.h"
+#include "ubus.h"
 #include "upd8255.h"
 #include "video.h"
 
@@ -120,7 +121,7 @@ uint8_t bus_io_in(ceda_ioaddr_t address) {
         }
     }
 
-    return 0;
+    return ubus_io_in(address);
 }
 
 void bus_io_out(ceda_ioaddr_t _address, uint8_t value) {
@@ -136,6 +137,8 @@ void bus_io_out(ceda_ioaddr_t _address, uint8_t value) {
             }
         }
     }
+
+    ubus_io_out(address, value);
 }
 
 void bus_init(CEDAModule *mod) {

src/ceda.c

@@ -1,5 +1,6 @@
 #include "ceda.h"
 
+// computer core
 #include "bios.h"
 #include "bus.h"
 #include "cli.h"
@@ -14,9 +15,13 @@
 #include "serial.h"
 #include "sio2.h"
 #include "speaker.h"
+#include "ubus.h"
 #include "upd8255.h"
 #include "video.h"
 
+// user peripherals
+#include "charmon.h"
+
 #include <assert.h>
 #include <unistd.h>
 
@@ -32,10 +37,12 @@ static CEDAModule mod_speaker;
 static CEDAModule mod_sio2;
 static CEDAModule mod_int;
 static CEDAModule mod_serial;
+static CEDAModule mod_ubus;
+static CEDAModule mod_charmon;
 
 static CEDAModule *modules[] = {
-    &mod_bios,  &mod_cli,     &mod_gui, &mod_bus,    &mod_cpu,
-    &mod_video, &mod_speaker, &mod_int, &mod_serial, &mod_sio2,
+    &mod_bios,    &mod_cli, &mod_gui,    &mod_bus,  &mod_cpu,  &mod_video,
+    &mod_speaker, &mod_int, &mod_serial, &mod_sio2, &mod_ubus, &mod_charmon,
 };
 
 void ceda_init(void) {
@@ -48,6 +55,8 @@ void ceda_init(void) {
     rom_bios_init(&mod_bios);
     video_init(&mod_video);
     speaker_init(&mod_speaker);
+    ubus_init(&mod_ubus);
+    charmon_init(&mod_charmon);
     bus_init(&mod_bus);
     cpu_init(&mod_cpu);
     int_init(&mod_int);

src/charmon.c

@@ -0,0 +1,26 @@
+#include "charmon.h"
+
+#include "conf.h"
+#include "ubus.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#define CHARMON_BASE (0xF0)
+
+void charmon_out(ceda_ioaddr_t address, uint8_t value) {
+    (void)address;
+    (void)putc(value, stdout);
+}
+
+void charmon_init(CEDAModule *mod) {
+    memset(mod, 0, sizeof(*mod));
+
+    bool *conf_installed = conf_getBool("mod", "charmon_installed");
+    bool installed = conf_installed ? *conf_installed : false;
+
+    if (!installed)
+        return;
+
+    ubus_register(CHARMON_BASE, CHARMON_BASE + 1, NULL, charmon_out);
+}

src/charmon.h

@@ -0,0 +1,10 @@
+#ifndef CEDA_CHAR_MONITOR_H
+#define CEDA_CHAR_MONITOR_H
+
+#include "module.h"
+#include "type.h"
+
+void charmon_init(CEDAModule *mod);
+void charmon_out(ceda_ioaddr_t address, uint8_t value);
+
+#endif // CEDA_CHAR_MONITOR_H

src/conf.c

@@ -23,6 +23,7 @@ static const char *CONF_PATH_HOME =
 // Emulator dynamic configuration
 static struct {
     bool cge_installed;
+    bool charmon_installed;
     ceda_string_t *bios_rom_path;
     ceda_string_t *char_rom_path;
     ceda_string_t *cge_rom_path;
@@ -46,6 +47,7 @@ typedef struct conf_tuple_t {
 
 static conf_tuple_t conf_tuples[] = {
     {"mod", "cge_installed", CONF_BOOL, &conf.cge_installed},
+    {"mod", "charmon_installed", CONF_BOOL, &conf.charmon_installed},
     {"path", "bios_rom", CONF_STR, &conf.bios_rom_path},
     {"path", "char_rom", CONF_STR, &conf.char_rom_path},
     {"path", "cge_rom", CONF_STR, &conf.cge_rom_path},

src/ubus.c

@@ -0,0 +1,83 @@
+#include "ubus.h"
+
+#include "conf.h"
+
+#include <stddef.h>
+#include <string.h>
+
+#define UBUS_MAX_PERIPHERALS (4)
+
+#define LOG_LEVEL LOG_LVL_INFO
+#include "log.h"
+
+struct ubus_io_slot {
+    ceda_ioaddr_t base;
+    uint32_t top;
+    ubus_io_read_t in;
+    ubus_io_write_t out;
+};
+
+static struct ubus_io_slot ubus_slots[UBUS_MAX_PERIPHERALS];
+static size_t ubus_used = 0;
+
+void ubus_init(CEDAModule *mod) {
+    memset(mod, 0, sizeof(*mod));
+
+    mod->init = ubus_init;
+}
+
+bool ubus_register(ceda_ioaddr_t base, uint32_t top, ubus_io_read_t read,
+                   ubus_io_write_t write) {
+    if (!read && !write)
+        return false;
+
+    if (top > 0x100)
+        return false;
+
+    if (top <= base)
+        return false;
+
+    if (ubus_used == UBUS_MAX_PERIPHERALS) {
+        LOG_WARN("Too many peripherals registered\n");
+        return false;
+    }
+
+    // check if peripherals are overlapping
+    for (size_t i = 0; i < ubus_used; ++i) {
+        struct ubus_io_slot *slot = &ubus_slots[i];
+        bool ok = (top <= slot->base) || (base >= slot->top);
+        if (!ok)
+            return false;
+    }
+
+    ubus_slots[ubus_used].base = base;
+    ubus_slots[ubus_used].top = top;
+    ubus_slots[ubus_used].in = read;
+    ubus_slots[ubus_used].out = write;
+    ubus_used += 1;
+
+    LOG_INFO("Registered peripheral at %02x\n", (unsigned int)base);
+
+    return true;
+}
+
+zuint8 ubus_io_in(ceda_ioaddr_t address) {
+    for (size_t i = 0; i < ubus_used; ++i) {
+        struct ubus_io_slot *slot = &ubus_slots[i];
+        if (address >= slot->base && address < slot->top)
+            if (slot->in)
+                return slot->in(address - slot->base);
+    }
+    return 0;
+}
+
+void ubus_io_out(ceda_ioaddr_t address, uint8_t value) {
+    for (size_t i = 0; i < ubus_used; ++i) {
+        struct ubus_io_slot *slot = &ubus_slots[i];
+        if (address >= slot->base && address < slot->top)
+            if (slot->out) {
+                slot->out(address - slot->base, value);
+                return;
+            }
+    }
+}

src/ubus.h

@@ -0,0 +1,37 @@
+#ifndef CEDA_USER_BUS_H
+#define CEDA_USER_BUS_H
+
+#include "module.h"
+#include "type.h"
+
+#include <stdbool.h>
+
+#include <Z80.h>
+
+typedef uint8_t (*ubus_io_read_t)(ceda_ioaddr_t address);
+typedef void (*ubus_io_write_t)(ceda_ioaddr_t address, uint8_t value);
+
+/**
+ * @brief Initialize the User Bus module.
+ *
+ * This module allows users to connect custom peripherals to the computer bus.
+ */
+void ubus_init(CEDAModule *mod);
+
+/**
+ * @brief Register a peripheral on the bus.
+ *
+ * @param base Peripheral base address.
+ * @param top Peripheral top address + 1 (eg. the first unused address)
+ * @param read IO input callback.
+ * @param write IO output callback.
+ *
+ * @return true in case of success, false otherwise.
+ */
+bool ubus_register(ceda_ioaddr_t base, uint32_t top, ubus_io_read_t read,
+                   ubus_io_write_t write);
+
+zuint8 ubus_io_in(ceda_ioaddr_t address);
+void ubus_io_out(ceda_ioaddr_t address, uint8_t value);
+
+#endif // CEDA_USER_BUS_H