Add USE_VGA_RES configuration for 640x480 display

This (practically) requires use of -DMEMSIZE=208 or larger, as it uses more
memory.  But, works nicely :)

CMakeLists.txt

@@ -35,6 +35,7 @@ set(SD_RX 4 CACHE STRING "SD SPI RX pin")
 set(SD_SCK 2 CACHE STRING "SD SPI SCK pin")
 set(SD_CS 5 CACHE STRING "SD SPI CS pin")
 set(SD_MHZ 5 CACHE STRING "SD SPI speed in MHz")
+option(USE_VGA_RES "Video uses VGA (640x480) resolution" OFF)
 
 # See below, -DMEMSIZE=<size in KB> will configure umac's memory size,
 # overriding defaults.
@@ -84,6 +85,15 @@ if (USE_SD)
    add_compile_definitions(SD_TX=${SD_TX} SD_RX=${SD_RX} SD_SCK=${SD_SCK} SD_CS=${SD_CS} SD_MHZ=${SD_MHZ})
 endif()
 
+if (USE_VGA_RES)
+   add_compile_definitions(USE_VGA_RES=1)
+   add_compile_definitions(DISP_WIDTH=640)
+   add_compile_definitions(DISP_HEIGHT=480)
+else()
+   add_compile_definitions(DISP_WIDTH=512)
+   add_compile_definitions(DISP_HEIGHT=342)
+endif()
+
 if (TARGET tinyusb_device)
   add_executable(firmware
     src/main.c

README.md

@@ -17,6 +17,8 @@ It has features, many features, the best features:
      disc storage on an SPI-attached SD card
    * Mac 128K by default, or you can make use of more of the Pico's
      memory and run as a _Mac 208K_
+   * Since you now have more memory, you can splash out on more
+     screen real-estate, and use 640x480 resolution!
 
 Great features.  It even doesn't hang at random!  (Anymore.)
 
@@ -57,6 +59,15 @@ This is because `umac` is used to patch the ROM, and when using
 unsupported sizes between 128K and 512K the RAM size can't be probed
 automatically, so the size needs to be embedded.
 
+This is also the case for altering the video resolution, because the ROM
+must be patched for this.  Build `umac` with `DISP_WIDTH=640 DISP_HEIGHT=480`
+when you intend to use the `USE_VGA_RES` option.  For example:
+
+```
+cd external/umac
+make MEMSIZE=208 DISP_WIDTH=640 DISP_HEIGHT=480
+```
+
 ## Build pico-umac
 
 Do the initial Pico SDK `cmake` setup into an out-of-tree build dir,
@@ -90,6 +101,11 @@ Options are required if you want SD support, or more than the default 128K of me
         writeable boot volume on SD) will allow _MacPaint_ to run.
       - **NOTE**: When this option is used, the ROM image must be
           built with an `umac` build with a corresponding `MEMSIZE`
+   * `-DUSE_VGA_RES=1`: Use 640x480 screen resolution instead of the
+     native 512x342.  This uses an additional 16KB of RAM, so this
+     option makes a _Mac 128K_ configuration virtually unusable.
+     It is recommended only to use this when configuring >208K
+     using the option above.
 
 Tip: `cmake` caches these variables, so if you see weird behaviour
 having built previously and then changed an option, delete the `build`
@@ -108,9 +124,10 @@ post-patching binary out:
 ```
 
 Note: Again, remember that if you are using the `-DMEMSIZE` option to
-increase the `pico-umac` memory, you will need to create this ROM
-image with a `umac` built with the corresponding `MEMSIZE` option, as
-above.
+increase the `pico-umac` memory, or the `-DUSE_VGA_RES` option to
+increase the `pico-umac` screen resolution, you will need to create
+this ROM image with a `umac` built with the corresponding
+`MEMSIZE`/`DISP_WIDTH`/`DISP_HEIGHT` options, as above.
 
 ## Disc image
 

src/video.c

@@ -65,8 +65,8 @@
 #define VIDEO_V_VIS_START       (VIDEO_VSW + VIDEO_VBP)
 #define VIDEO_V_VIS_END         (VIDEO_V_VIS_START + VIDEO_VRES)
 
-#define VIDEO_FB_HRES           512
-#define VIDEO_FB_VRES           342
+#define VIDEO_FB_HRES           DISP_WIDTH
+#define VIDEO_FB_VRES           DISP_HEIGHT
 
 /* The lines at which the FB data is actively output: */
 #define VIDEO_FB_V_VIS_START    (VIDEO_V_VIS_START + ((VIDEO_VRES - VIDEO_FB_VRES)/2))