minimalistic scheduler is working

build/Makefile

@@ -131,12 +131,18 @@ $(PATH_BIN)/refapp.8xp :
 	@-$(ECHO)
 	@-$(ECHO) +++ assembling $(notdir $(PATH_SRC)/startup/crt0.s)
 	@-$(AS) $(AFLAGS) -c -o $(PATH_OBJ)/crt0.rel $(PATH_SRC)/startup/crt0.s
-	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/app/app_led_util.c)
+	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/app/app_hello.c)
+	@-$(CC) $(CFLAGS) -c -o $(PATH_OBJ)/app_hello.rel $(PATH_SRC)/app/app_hello.c
+	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/app/app_led.c)
+	@-$(CC) $(CFLAGS) -c -o $(PATH_OBJ)/app_led.rel $(PATH_SRC)/app/app_led.c
+	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/mcal/app/app_led_util.c)
 	@-$(CC) $(CFLAGS) -c -o $(PATH_OBJ)/app_led_util.rel $(PATH_SRC)/app/app_led_util.c
 	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/mcal/mcal_gpt.c)
 	@-$(CC) $(CFLAGS) -c -o $(PATH_OBJ)/mcal_gpt.rel $(PATH_SRC)/mcal/mcal_gpt.c
-	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/app/app_led.c) and linking/extracting to $(notdir $(PATH_BIN)/refapp.ihx)
-	@-$(CC) $(CFLAGS) -o $(PATH_BIN)/refapp.ihx $(PATH_SRC)/app/app_led.c $(PATH_OBJ)/app_led_util.rel $(PATH_OBJ)/crt0.rel $(PATH_OBJ)/mcal_gpt.rel
+	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/os/os.c)
+	@-$(CC) $(CFLAGS) -c -o $(PATH_OBJ)/os.rel $(PATH_SRC)/os/os.c
+	@-$(ECHO) +++ compiling $(notdir $(PATH_SRC)/app/app_main.c) and linking/extracting to $(notdir $(PATH_BIN)/refapp.ihx)
+	@-$(CC) $(CFLAGS) -o $(PATH_BIN)/refapp.ihx $(PATH_SRC)/app/app_main.c $(PATH_OBJ)/app_led.rel $(PATH_OBJ)/app_led_util.rel $(PATH_OBJ)/app_hello.rel $(PATH_OBJ)/crt0.rel $(PATH_OBJ)/mcal_gpt.rel $(PATH_OBJ)/os.rel
 	@-$(ECHO) +++ creating binary $(notdir $(PATH_BIN)/refapp.bin)
 	@-$(OBJCOPY) -Iihex -Obinary $(PATH_BIN)/refapp.ihx $(PATH_BIN)/refapp.bin
 	@-$(ECHO) +++ creating on-calc app $(notdir $(PATH_BIN)/refapp.8xp)

build/ti84-ref_app.vcxproj

@@ -13,13 +13,17 @@
     <None Include="Makefile" />
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="..\src\app\app_hello.c" />
     <ClCompile Include="..\src\app\app_led.c" />
     <ClCompile Include="..\src\app\app_led_util.c" />
+    <ClCompile Include="..\src\app\app_main.c" />
     <ClCompile Include="..\src\mcal\mcal_gpt.c" />
+    <ClCompile Include="..\src\os\os.c" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\src\app\app_led_util.h" />
     <ClInclude Include="..\src\mcal\mcal_gpt.h" />
+    <ClInclude Include="..\src\os\os.h" />
     <ClInclude Include="..\src\startup\asm_util.h" />
   </ItemGroup>
   <PropertyGroup Label="Globals">

build/ti84-ref_app.vcxproj.filters

@@ -25,6 +25,9 @@
     <Filter Include="src\mcal">
       <UniqueIdentifier>{40bb87ba-a6ab-435a-aa98-6a436693e6ab}</UniqueIdentifier>
     </Filter>
+    <Filter Include="src\os">
+      <UniqueIdentifier>{56938916-c213-486a-b3b1-22d39f753f45}</UniqueIdentifier>
+    </Filter>
   </ItemGroup>
   <ItemGroup>
     <None Include="Makefile">
@@ -50,6 +53,15 @@
     <ClCompile Include="..\src\mcal\mcal_gpt.c">
       <Filter>src\mcal</Filter>
     </ClCompile>
+    <ClCompile Include="..\src\os\os.c">
+      <Filter>src\os</Filter>
+    </ClCompile>
+    <ClCompile Include="..\src\app\app_hello.c">
+      <Filter>src\app</Filter>
+    </ClCompile>
+    <ClCompile Include="..\src\app\app_main.c">
+      <Filter>src\app</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\src\app\app_led_util.h">
@@ -61,5 +73,8 @@
     <ClInclude Include="..\src\mcal\mcal_gpt.h">
       <Filter>src\mcal</Filter>
     </ClInclude>
+    <ClInclude Include="..\src\os\os.h">
+      <Filter>src\os</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

readme.md

@@ -15,23 +15,26 @@ for the z80-based TI-84 Plus monochrome graphics calculator. It runs in the
 open `Asm(prgm)` interface provided in the calculator's `CATALOG` menu.
 It uses the TI-84's on-board Z80 processor.
 
-The reference application implements a small _blinky_ show.
+The reference application implements parallel _blinky_/_hello_-_world_ test-shows.
+A minimalistic cooperative multitasking scheduler controls
+the presentation of ASCII-text messages.
 
-The ASCII-text _ON_/_OFF_ is written on the calculator screen.
+The text-shows _ON_/_OFF_ and _hello_/_world_ are written on the calculator screen.
 Text is used since there is no actual LED present on the calculator-target system.
-This is intended to simulate an LED-blinky by _toggling_ between _ON_ and _OFF_.
+This is intended to simulate an LED-blinky by _toggling_ between _ON_ and _OFF_
+and support an independent _hello_-_world_-task as well.
+The _ON_/_OFF_ messages are printed every $1s$ and the _hello_/_world_ messages every $3s$.
 
-The blinky _ON_/_OFF_ timebase is derived from a $1s$ tick,
-resulting in a toggle-frequency of ${\sim}{\frac{1}{2}}Hz$.
+The cooperative multitasking timebase is derived from a $1s$ tick.
 The underlying 32-bit timer resides on ports `0x45`-`0x48`,
 where the lower byte at port `0x45` is used.
 This timer is only available on the TI-84, not the TI-83.
 
-The blinky _ON_/_OFF_ text messages are printed
-at row $2$, column $7$.
+The blinky _ON_/_OFF_ and _hello_/_world_ text messages are printed
+at rows $2$ and $3$, respectively, and both at column $6$.
 
 A skinny `main()` subroutine in the soruce file
-[`app_led.c`](./src/app/app_led.c) controls the toggling.
+[`app_main.c`](./src/app/app_main.c) controls the program flow.
 The application is written in high-level C17.
 There is minimal use of assembly for startup and to interface with
 [TI-83 Plus System Routines](https://education.ti.com/html/eguides/discontinued/computer-software/EN/SDK-TI-83-System-Routines_EN.pdf).
@@ -111,7 +114,7 @@ Personally. I do not consider this to be a $100\\%$ sound basis
 for project reliability and/or stability.
 
 Nonetheless, empirical evidence shows a working,
-and fully/properly initialized C-language application.
+and fully/properly initialized C-language, non-trivial application.
 It provides a basis that seems to adhere to the established,
 common rules of modern C. Larger projects could be built or modelled
 from this.

src/app/app_hello.c

@@ -0,0 +1,59 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2024.
+//  Distributed under The Unlicense
+//
+
+#include <stdbool.h>
+
+#include <app/app_led_util.h>
+
+static void app_hello_hello(void);
+static void app_hello_world(void);
+static void app_hello_clear(void);
+
+static bool app_hello_is_hello;
+
+
+void app_hello_init(void)
+{
+}
+
+void app_hello_task(void)
+{
+  app_hello_clear();
+
+  (!app_hello_is_hello) ? app_hello_hello() : app_hello_world();
+
+  app_hello_is_hello = (bool) (!app_hello_is_hello);
+}
+
+static void app_hello_hello(void)
+{
+  app_led_util_home2();
+  app_led_util_putc('h');
+  app_led_util_putc('e');
+  app_led_util_putc('l');
+  app_led_util_putc('l');
+  app_led_util_putc('o');
+}
+
+static void app_hello_world(void)
+{
+  app_led_util_home2();
+  app_led_util_putc('w');
+  app_led_util_putc('o');
+  app_led_util_putc('r');
+  app_led_util_putc('l');
+  app_led_util_putc('d');
+}
+
+static void app_hello_clear(void)
+{
+  app_led_util_home2();
+  app_led_util_putc(' ');
+  app_led_util_putc(' ');
+  app_led_util_putc(' ');
+  app_led_util_putc(' ');
+  app_led_util_putc(' ');
+}
+

src/app/app_led.c

@@ -4,88 +4,47 @@
 //
 
 #include <app/app_led_util.h>
-#include <mcal/mcal_gpt.h>
 
-static void app_led_on   (void);
-static void app_led_off  (void);
-static void app_led_clr  (void);
-static void app_led_delay(void);
+static void app_led_on (void);
+static void app_led_off(void);
+static void app_led_clr(void);
 
-static uint8_t app_led_current_tick;
-static bool    app_led_exit_flag;
+static bool app_led_is_on;
 
-void main(void)
+void app_led_init(void)
 {
   app_led_util_init();
+}
 
-  mcal_gpt_init();
-
-  app_led_current_tick = mcal_gpt_get_time_elapsed();
-
-  for(;;)
-  {
-    app_led_clr();
-    app_led_on();
-    app_led_delay();
-
-    if(app_led_exit_flag)
-    {
-      break;
-    }
-
-    app_led_clr();
-    app_led_off();
-    app_led_delay();
-
-    if(app_led_exit_flag)
-    {
-      break;
-    }
-  }
-
-  mcal_gpt_de_init();
+void app_led_task(void)
+{
+  app_led_clr();
 
-  // Exit the Application and return to the home screen
-  // using the JForceCmdNoChar function. See also page 16
-  // in "TI-83 Plus System Routines", Third Release,
-  // (Jan. 25, 2002).
+  (!app_led_is_on) ? app_led_on() : app_led_off();
 
-  __asm__("rst 0x28\n" ".dw #0x4027\n");
+  app_led_is_on = (bool) (!app_led_is_on);
 }
 
 static void app_led_on(void)
 {
-  app_led_util_home();
+  app_led_util_home1();
   app_led_util_putc('O');
   app_led_util_putc('N');
+  app_led_util_putc(' ');
 }
 
 static void app_led_off(void)
 {
-  app_led_util_home();
+  app_led_util_home1();
   app_led_util_putc('O');
   app_led_util_putc('F');
   app_led_util_putc('F');
 }
 
 static void app_led_clr(void)
 {
-  app_led_util_home();
+  app_led_util_home1();
   app_led_util_putc(' ');
   app_led_util_putc(' ');
   app_led_util_putc(' ');
 }
-
-static void app_led_delay(void)
-{
-  uint8_t next_tick;
-
-  do
-  {
-    next_tick         = mcal_gpt_get_time_elapsed();
-    app_led_exit_flag = app_led_util_wants_exit();
-  }
-  while((next_tick == app_led_current_tick) && (!app_led_exit_flag));
-
-  app_led_current_tick = next_tick;
-}

src/app/app_led_util.c

@@ -13,35 +13,31 @@ void app_led_util_putc(char c) ATTRIBUTE_NAKED
   __asm__("ret\n");
 }
 
-void app_led_util_home(void) ATTRIBUTE_NAKED
+void app_led_util_home1(void) ATTRIBUTE_NAKED
 {
   __asm__("ld b,#0x02\n");
   __asm__("ld a,b\n");
   __asm__("ld (#0x844B), a\n");
-  __asm__("ld b,#0x07\n");
+  __asm__("ld b,#0x06\n");
   __asm__("ld a,b\n");
   __asm__("ld (#0x844C), a\n");
   __asm__("ret\n");
 }
 
-void app_led_util_init(void) ATTRIBUTE_NAKED
+void app_led_util_home2(void) ATTRIBUTE_NAKED
 {
-  __asm__("rst 0x28\n" ".dw #0x4540\n");
-  __asm__("rst 0x28\n" ".dw #0x4558\n");
+  __asm__("ld b,#0x03\n");
+  __asm__("ld a,b\n");
+  __asm__("ld (#0x844B), a\n");
+  __asm__("ld b,#0x06\n");
+  __asm__("ld a,b\n");
+  __asm__("ld (#0x844C), a\n");
   __asm__("ret\n");
 }
 
-bool app_led_util_wants_exit(void) ATTRIBUTE_NAKED
+void app_led_util_init(void) ATTRIBUTE_NAKED
 {
-  __asm__("rst 0x28\n" ".dw #0x4018\n");
-  __asm__("ld h, #0x0\n");
-  __asm__("cp #0x9\n");
-  __asm__("jp nz, no_exit\n");
-  __asm__("ld h, #0x1\n");
-  __asm__("no_exit:\n");
+  __asm__("rst 0x28\n" ".dw #0x4540\n");
+  __asm__("rst 0x28\n" ".dw #0x4558\n");
   __asm__("ret\n");
-
-  #if defined(_MSC_VER)
-  return false;
-  #endif
 }

src/app/app_led_util.h

@@ -3,8 +3,8 @@
 //  Distributed under The Unlicense
 //
 
-#ifndef APP_LED_UTIL_2024_01_7_H
-  #define APP_LED_UTIL_2024_01_7_H
+#ifndef APP_LED_UTIL_2024_01_07_H
+  #define APP_LED_UTIL_2024_01_07_H
 
   #include <stdbool.h>
   #include <stdint.h>
@@ -25,8 +25,9 @@
   // _PutC             #0x4504
 
   void app_led_util_putc      (char c) ATTRIBUTE_NAKED;
-  void app_led_util_home      (void)   ATTRIBUTE_NAKED;
+  void app_led_util_home1     (void)   ATTRIBUTE_NAKED;
+  void app_led_util_home2     (void)   ATTRIBUTE_NAKED;
   void app_led_util_init      (void)   ATTRIBUTE_NAKED;
   bool app_led_util_wants_exit(void)   ATTRIBUTE_NAKED;
 
-#endif // APP_UTIL_2024_01_7_H
+#endif // APP_UTIL_2024_01_07_H

src/app/app_main.c

@@ -0,0 +1,26 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2024.
+//  Distributed under The Unlicense
+//
+
+#include <mcal/mcal_gpt.h>
+#include <os/os.h>
+#include <startup/asm_util.h>
+
+void main(void)
+{
+  mcal_gpt_init();
+
+  os_init();
+
+  os_schedule();
+
+  mcal_gpt_de_init();
+
+  // Exit the Application and return to the home screen
+  // using the JForceCmdNoChar function. See also page 16
+  // in "TI-83 Plus System Routines", Third Release,
+  // (Jan. 25, 2002).
+
+  __asm__("rst 0x28\n" ".dw #0x4027\n");
+}

src/mcal/mcal_gpt.h

@@ -3,13 +3,13 @@
 //  Distributed under The Unlicense
 //
 
-#ifndef MCAL_GPT_2024_01_7_H
-  #define MCAL_GPT_2024_01_7_H
+#ifndef MCAL_GPT_2024_01_07_H
+  #define MCAL_GPT_2024_01_07_H
 
   #include <stdint.h>
 
   void    mcal_gpt_init            (void);
   void    mcal_gpt_de_init         (void);
   uint8_t mcal_gpt_get_time_elapsed(void);
 
-#endif //CLOCK_2024_01_7_H
+#endif // MCAL_GPT_2024_01_07_H