Merge pull request #201 from fruit-bat/feature/CVBS

Implement 50Hz CVBS output

README.md

@@ -23,6 +23,10 @@ This project is intended to be relatively easy to breadboard or prototype in som
 
 ## Updates
 
+28/12/24
+
+* Added a build with CVBS 50Hz output - credit to [svofski](https://github.com/svofski)
+
 27/12/24
 
 * Additions for Murmulator 2 (only mono PWM audio for now)
@@ -111,6 +115,7 @@ Click on the images below for more information ...
 | [MURMULATOR](docs/MURMULATOR.md) | Micro with VGA/HDMI and more |
 | [MURMULATOR2](docs/MURMULATOR2.md) | Micro with VGA/HDMI and more |
 | [RP2040-PiZero](docs/ZxSpectrumPiZero.md) | Waveshare RP2040-PiZero Development Board |
+| [CVBS 50Hz](docs/ZxSpectrumCVBS.md) | Unknown/breadboard with 50Hz CVBS output |
 
 ## Screen shots
 <img src="docs/screenshots/48k_boot_screen.png" height="200px"/> <img src="docs/screenshots/128k_boot_screen.png" height="200px"/> <img src="docs/screenshots/the_swarm_is_coming_1.png" height="200px"/> <img src="docs/screenshots/the_swarm_is_coming_2.png" height="200px"/> <img src="docs/screenshots/the_goblin_1.png" height="200px"/> <img src="docs/screenshots/the_goblin_2.png" height="200px"/> <img src="docs/screenshots/menu_main_vol.png" height="200px"/>

docs/ZxSpectrumCVBS.md

@@ -0,0 +1,38 @@
+### ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz
+
+This is a target based on ZxSpectrum4PinAudioVga1111Ps2 but it generates timings compatible with composite PAL TV.<br/>
+
+It can be connected to a black and white set with a help of this schematic:
+![image](cvbs_grayscale.png)
+Alternatively RGBI outputs can be connected to a PAL modulator.
+
+It supports the following:
+* USB keyboard
+* PS/2 keyboard (untested)
+* USB joysticks
+* VGA video (RGBY1111)
+* I2S sound
+* SPI SD card
+* Serial port debug
+
+This target uses I2S DAC (PCM5102).
+| Pin | Function |
+| - | - |
+| 2 | SD SCK |
+| 3 | SD MOSI |
+| 4 | SD MISO |
+| 5 | SD CS |
+| 12 | RED |
+| 13 | GREEN |
+| 14 | BLUE |
+| 15 | INTENSITY |
+| 16 | CSYNC |
+| 26 | I2S DATA |
+| 27 | I2S BCLK |
+| 28 | I2S LRCK |
+
+#### Firmware
+
+| Display | Audio | Firmware Pico | Firmware Pico 2 |
+| - | - | - | - |
+| CVBS 50Hz | I2S | [ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz](/uf2-rp2040/ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz.uf2) | 

src/CMakeLists.txt

@@ -171,7 +171,8 @@ add_dependencies (ZxSpectrumBreadboard
   ZxSpectrum4PinAudioVga1111Ps2_640x480x60Hz
   ZxSpectrum4PinAudioVga1111Ps2_720x576x50Hz
   ZxSpectrum4PinAudioVga222Ps2_640x480x60Hz
-  ZxSpectrum4PinAudioVga222Ps2_720x576x50Hz  
+  ZxSpectrum4PinAudioVga222Ps2_720x576x50Hz
+  ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz
 )
 if ((${PICO_BOARD} STREQUAL "pico") OR (${PICO_BOARD} STREQUAL "pico2"))
   message("Relevant target: ZxSpectrumBreadboard")

src/ZxScanlineVgaRenderLoop.cpp

@@ -78,13 +78,92 @@ const scanvideo_mode_t vga_mode_720x288_50 =
   .yscale = 2,
 };
 
+#if CVBS_13_5MHZ
+// timing definition based on 13.5MHz pixel clock (270MHz core)
+// 312 lines, 50.08 frames per second (matches 48K specs)
+const scanvideo_timing_t cvbs_timing_50hz_13_5MHz =
+{
+    .clock_freq = 13500000,
+
+    .h_active = 720,
+    .v_active = 288,
+
+    .h_front_porch = 14,
+    .h_pulse = 68,
+    .h_total = 864,
+    .h_sync_polarity = 1 | CSYNC_EXTEND, // fill in vsync with eq pulses
+
+    .v_front_porch = 5,
+    .v_pulse = 5,
+    .v_total = 312,
+    .v_sync_polarity = 1,
+
+    .enable_clock = 0,
+    .clock_polarity = 0,
+
+    .enable_den = 0
+};
+
+const scanvideo_mode_t cvbs_mode_50 =
+{
+    .default_timing = &cvbs_timing_50hz_13_5MHz,
+    .pio_program = &video_24mhz_composable,
+    .width = 720,
+    .height = 256,
+    .xscale = 1,
+    .yscale = 1,
+};
+#endif
+
+#if CVBS_12MHZ
+// timing definition based on 12MHz pixel clock (240MHz core)
+// 312 lines, 50.08 frames per second (matches 48K specs)
+const scanvideo_timing_t cvbs_timing_50hz_12MHz =
+{
+    .clock_freq = 12000000,
+
+    .h_active = 640,    // visible area 64+512+64
+    .v_active = 288,    // visible area 16+256+16
+
+    .h_front_porch = 12,
+    .h_pulse = 60,
+    .h_total = 768,
+    .h_sync_polarity = 1 | CSYNC_EXTEND, // fill in vsync with eq pulses
+
+    .v_front_porch = 5,
+    .v_pulse = 5,
+    .v_total = 312,
+    .v_sync_polarity = 1,
+
+    .enable_clock = 0,
+    .clock_polarity = 0,
+
+    .enable_den = 0
+};
+
+const scanvideo_mode_t cvbs_mode_50 =
+{
+    .default_timing = &cvbs_timing_50hz_12MHz,
+    .pio_program = &video_24mhz_composable,
+    .width = 640,
+    .height = 256,
+    .xscale = 1,
+    .yscale = 1,
+};
+#endif
+
+
 #ifndef VGA_MODE
 #define VGA_MODE vga_mode_640x240_60
 #endif  
 
 void ZxScanlineVgaRenderLoopInit()
 {
+#if (CVBS_12MHZ || CVBS_13_5MHZ)
+  set_sys_clock_khz(2 * VGA_MODE.default_timing->clock_freq / 100, true);
+#else
   set_sys_clock_khz(VGA_MODE.default_timing->clock_freq / 100, true);
+#endif
   sleep_ms(10);
 }
 

src/vga/CMakeLists.txt

@@ -49,11 +49,32 @@ set(zxspectrum_vga_720x576x50Hz_defines
   PICO_SCANVIDEO_MAX_SCANLINE_BUFFER_WORDS=800
 )
 
+set(zxspectrum_vga_CVBSx50Hz_defines
+  # Set the resolution of the menu screen
+  PCS_COLS=80
+  PCS_ROWS=30
+  SZ_FRAME_X=5
+  # Set the VGA timing
+  VGA_MODE=cvbs_mode_50
+  # different pixel clock variants, pick one
+  #CVBS_13_5MHZ=1
+  CVBS_12MHZ=1
+  # The display resolution
+  DISPLAY_WIDTH_PIXELS=640
+  DISPLAY_HEIGHT_PIXELS=576 # halved to 288
+  # The default interrupt source
+  ZX_SPECTRUM_INT_SRC=SyncToDisplay
+  # TODO work what this is
+  PICO_SCANVIDEO_MAX_SCANLINE_BUFFER_WORDS=800
+)
+
+
 foreach(target
   ZxSpectrum4PinAudioVga1111Ps2_640x480x60Hz
   ZxSpectrum4PinAudioVga1111Ps2_720x576x50Hz
   ZxSpectrum4PinAudioVga222Ps2_640x480x60Hz
   ZxSpectrum4PinAudioVga222Ps2_720x576x50Hz
+  ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz
 )
   add_executable(${target}
     ${zxspectrum_common_src}
@@ -84,6 +105,15 @@ foreach(target
 
 endforeach()
 
+foreach(target
+  ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz
+)
+  pico_generate_pio_header(${target}
+    ${zxspectrum_audio_i2s_pio}
+  )
+
+endforeach()
+
 set(ZxSpectrum4PinAudioVga1111Ps2_defines
   # VGA 1111
   VGA_ENC_RGBY_1111
@@ -106,6 +136,29 @@ set(ZxSpectrum4PinAudioVga1111Ps2_defines
   USE_PS2_KBD
 )
 
+set(ZxSpectrumI2SAudioVga1111Ps2_defines
+  # VGA 1111
+  VGA_ENC_RGBY_1111
+  PICO_SCANVIDEO_COLOR_PIN_COUNT=4u
+  PICO_SCANVIDEO_DPI_PIXEL_RCOUNT=2u
+  PICO_SCANVIDEO_DPI_PIXEL_GCOUNT=1u
+  PICO_SCANVIDEO_DPI_PIXEL_BCOUNT=1u
+  PICO_SCANVIDEO_DPI_PIXEL_RSHIFT=2u
+  PICO_SCANVIDEO_DPI_PIXEL_GSHIFT=1u
+  PICO_SCANVIDEO_DPI_PIXEL_BSHIFT=0u
+  PICO_SCANVIDEO_COLOR_PIN_BASE=12u
+
+  # Configure the I2S audio, pio1 SM ?
+  PICO_AUDIO_I2S=1
+  PICO_AUDIO_I2S_PIO=pio1
+  PICO_AUDIO_I2S_PIO_FUNC=GPIO_FUNC_PIO1
+  PICO_AUDIO_I2S_DATA=26
+  PICO_AUDIO_I2S_BCLK=27
+
+  # Enable the PS/2 keyboard
+  USE_PS2_KBD
+)
+
 target_compile_definitions(ZxSpectrum4PinAudioVga1111Ps2_720x576x50Hz PRIVATE
   ${picomputer_vga_defines}
   ${ZxSpectrum4PinAudioVga1111Ps2_defines}
@@ -118,6 +171,12 @@ target_compile_definitions(ZxSpectrum4PinAudioVga1111Ps2_640x480x60Hz PRIVATE
   ${zxspectrum_vga_640x480x60Hz_defines}
 )
 
+target_compile_definitions(ZxSpectrumI2SAudioVga1111Ps2_CVBSx50Hz PRIVATE
+  ${picomputer_vga_defines}
+  ${ZxSpectrumI2SAudioVga1111Ps2_defines}
+  ${zxspectrum_vga_CVBSx50Hz_defines}
+)
+
 ########################################################################
 # VGA 222 on breadboard with PS/2 keyboard
 ########################################################################