From 6292c1101121bc8ba2db752cab3cbe41469b29d0 Mon Sep 17 00:00:00 2001
From: lonkaars <loek@pipeframe.xyz>
Date: Thu, 30 Mar 2023 15:10:17 +0200
Subject: new spi system

---
 basys3/basys3.srcs/io.xdc                   |  4 +-
 basys3/basys3.srcs/ppu_addr_dec.vhd         | 13 ++---
 basys3/basys3.srcs/spi.vhd                  | 39 +++++++++------
 basys3/basys3.srcs/spi_tb.vhd               | 78 ++++++++++++++---------------
 basys3/basys3.srcs/top.vhd                  | 22 ++++----
 basys3/basys3.xpr                           | 10 +++-
 docs/hardware/pinout.md                     |  3 +-
 src/main.c                                  | 12 +++--
 src/ppu/consts.h                            |  6 +++
 src/ppu/internals.c                         | 29 ++++++++++-
 src/ppu/internals.h                         | 10 +++-
 src/ppu/stm.c                               | 15 ++----
 src/ppusim/mem.c                            | 14 ++++--
 src/stm32/main.c                            |  6 ++-
 test/ppu-stm-integration-demo/data2test.awk | 15 ++++++
 test/ppu-stm-integration-demo/makefile      |  8 +--
 16 files changed, 178 insertions(+), 106 deletions(-)
 create mode 100755 test/ppu-stm-integration-demo/data2test.awk

diff --git a/basys3/basys3.srcs/io.xdc b/basys3/basys3.srcs/io.xdc
index 8243f1e..419e4cd 100644
--- a/basys3/basys3.srcs/io.xdc
+++ b/basys3/basys3.srcs/io.xdc
@@ -41,10 +41,10 @@ set_property PACKAGE_PIN L18 [get_ports {B[1]}]
 set_property PACKAGE_PIN N18 [get_ports {B[0]}]
 
 set_property IOSTANDARD LVCMOS33 [get_ports VBLANK]
-set_property IOSTANDARD LVCMOS33 [get_ports WEN]
+set_property IOSTANDARD LVCMOS33 [get_ports SPI_RESET]
 
 set_property PACKAGE_PIN C16 [get_ports VBLANK]
-set_property PACKAGE_PIN J1 [get_ports WEN]
+set_property PACKAGE_PIN J1 [get_ports SPI_RESET]
 
 
 
diff --git a/basys3/basys3.srcs/ppu_addr_dec.vhd b/basys3/basys3.srcs/ppu_addr_dec.vhd
index 33f247c..649d582 100644
--- a/basys3/basys3.srcs/ppu_addr_dec.vhd
+++ b/basys3/basys3.srcs/ppu_addr_dec.vhd
@@ -20,7 +20,7 @@ entity ppu_addr_dec is port( -- address decoder
 end ppu_addr_dec;
 
 architecture Behavioral of ppu_addr_dec is
-	signal TMM_RANGE, BAM_RANGE, FAM_RANGE, PAL_RANGE, AUX_RANGE : std_logic := '0'; -- ADDR in range of memory area
+	signal NUL_RANGE, TMM_RANGE, BAM_RANGE, FAM_RANGE, PAL_RANGE, AUX_RANGE : std_logic := '0'; -- ADDR in range of memory area
 begin
 	-- address MUX
 	TMM_ADDR <= ADDR(PPU_TMM_ADDR_WIDTH-1 downto 0);
@@ -29,12 +29,13 @@ begin
 	PAL_ADDR <= ADDR(PPU_PAL_ADDR_WIDTH-1 downto 0);
 	AUX_ADDR <= ADDR(PPU_AUX_ADDR_WIDTH-1 downto 0);
 
+	NUL_RANGE <= '1' when (and ADDR) else '0'; -- address is 0xffff
 	-- WEN MUX
-	TMM_WEN <= TMM_RANGE and WEN;
-	BAM_WEN <= BAM_RANGE and WEN;
-	FAM_WEN <= FAM_RANGE and WEN;
-	PAL_WEN <= PAL_RANGE and WEN;
-	AUX_WEN <= AUX_RANGE and WEN;
+	TMM_WEN <= TMM_RANGE and WEN and (not NUL_RANGE);
+	BAM_WEN <= BAM_RANGE and WEN and (not NUL_RANGE);
+	FAM_WEN <= FAM_RANGE and WEN and (not NUL_RANGE);
+	PAL_WEN <= PAL_RANGE and WEN and (not NUL_RANGE);
+	AUX_WEN <= AUX_RANGE and WEN and (not NUL_RANGE);
 
 	-- address ranges
 	TMM_RANGE <= '1' when not ((ADDR(15) and ADDR(14) and ADDR(13)) or (ADDR(15) and ADDR(14) and ADDR(12))) else '0';
diff --git a/basys3/basys3.srcs/spi.vhd b/basys3/basys3.srcs/spi.vhd
index a09d5df..d0e918e 100644
--- a/basys3/basys3.srcs/spi.vhd
+++ b/basys3/basys3.srcs/spi.vhd
@@ -6,10 +6,11 @@ use work.ppu_consts.all;
 
 entity spi is port (
 	SYSCLK : in std_logic; -- clock basys3 100MHz
-	SPI_CLK : in std_logic; -- incoming clock of SPI
-	SPI_MOSI : in std_logic; -- incoming data of SPI
 	RESET : in std_logic; -- async reset
-	DATA : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '0')); --	data read
+	DCK : in std_logic; -- data clock (spi format)
+	DI : in std_logic; -- data in (spi format)
+	DO : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '1'); --	data out (parallel)
+	WEN : out std_logic := '0'); -- write enable (triggers during each word to propagate previous word)
 end spi;
 
 architecture Behavioral of spi is
@@ -17,37 +18,45 @@ architecture Behavioral of spi is
 	signal dataFF0,dataFF1,dataFF2,dataFF3 : std_logic := '0'; -- signal for metastability synchronizer of data SPI
 
 	constant COUNTER_RESET_VALUE : integer := PPU_RAM_BUS_ADDR_WIDTH + PPU_RAM_BUS_DATA_WIDTH - 1;
+	signal DBG_I : integer range 0 to COUNTER_RESET_VALUE := COUNTER_RESET_VALUE; -- counter for data position
 begin
 	process (SYSCLK)
-		variable bit_idx : integer range 0 to COUNTER_RESET_VALUE := COUNTER_RESET_VALUE; -- counter for data position
-		variable spi_reg : std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '0');
+		variable i : integer range 0 to COUNTER_RESET_VALUE := COUNTER_RESET_VALUE; -- counter for data position
+		variable data_r : std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '1'); -- data register
 	begin
 		if RESET = '1' then
-			 spi_reg := (others => '0');
-			 bit_idx := COUNTER_RESET_VALUE;
-			 DATA <= (others => '0');
+			data_r := (others => '1');
+			i := COUNTER_RESET_VALUE;
+			DBG_I <= i;
+			DO <= (others => '1');
+			WEN <= '0';
 		elsif rising_edge(SYSCLK) then
 			-- flip flop for clk SPI to synchronise a
-			clkFF0 <= SPI_CLK;
+			clkFF0 <= DCK;
 			clkFF1 <= clkFF0;
 			clkFF2 <= clkFF1;
 			clkFF3 <= clkFF2;
 			-- flip flop for data SPI to synchronise
-			dataFF0 <= SPI_MOSI;
+			dataFF0 <= DI;
 			dataFF1 <= dataFF0;
 			dataFF2 <= dataFF1;
 			dataFF3 <= dataFF2;
 
 			if (clkFF3 = '0' and clkFF2 = '1') then -- check for rising edge of clk SPI
-				spi_reg(bit_idx) := dataFF3; -- load new data into temporary register
+				data_r(i) := dataFF3; -- load new data into temporary register
 
-				if bit_idx = 0 then
-					bit_idx := COUNTER_RESET_VALUE; -- reset bit index
-					DATA <= spi_reg; -- flush temporary register to data outpu
+				if i = 0 then
+					i := COUNTER_RESET_VALUE; -- reset bit index
+					DO <= data_r; -- flush temporary register to data outpu
 				else
-					bit_idx := bit_idx - 1; -- decrement bit index
+					i := i - 1; -- decrement bit index
 				end if;
+
+				-- propagate previous command to ppu during second byte of current command
+				if i = 23 then WEN <= '1'; end if;
+				if i = 15 then WEN <= '0'; end if;
 			end if;
+		DBG_I <= i;
 		end if;
 	end process;
 end Behavioral;
diff --git a/basys3/basys3.srcs/spi_tb.vhd b/basys3/basys3.srcs/spi_tb.vhd
index f6e2d21..8e4b8aa 100644
--- a/basys3/basys3.srcs/spi_tb.vhd
+++ b/basys3/basys3.srcs/spi_tb.vhd
@@ -12,18 +12,18 @@ end spi_tb;
 architecture behavioral of spi_tb is
 	signal SYSCLK : std_logic := '0';
 	signal SPI_CLK : std_logic := '0';
-	signal SPI_MOSI : std_logic := '0';
+	signal SPI_DATA : std_logic := '0';
 	signal RESET : std_logic := '0';
-	signal DATA : std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '0');
 begin
 	uut : entity work.spi port map(
 		SYSCLK => SYSCLK,
 		RESET => RESET,
-		DATA => DATA,
-		SPI_CLK => SPI_CLK,
-		SPI_MOSI => SPI_MOSI);
+		DO => open,
+		DI => SPI_DATA,
+		DCK => SPI_CLK,
+		WEN => open);
 
-	sysclkgen: process
+	process
 	begin
 		for i in 0 to 10000 loop
 			wait for 5 ns;
@@ -34,197 +34,197 @@ begin
 		wait; -- stop for simulator
 	end process;
 
-	spi_data: process
+	process
 	begin
 		for i in 0 to 2 loop
 			-- data = 0b01010110010100001001110011111111 (0x56509cff)
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '0';
+			SPI_DATA <= '0';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '0';
 
-			SPI_MOSI <= '1';
+			SPI_DATA <= '1';
 			wait for 50 ns;
 			SPI_CLK <= '1';
 			wait for 50 ns;
diff --git a/basys3/basys3.srcs/top.vhd b/basys3/basys3.srcs/top.vhd
index ed1c3b0..1c58b60 100644
--- a/basys3/basys3.srcs/top.vhd
+++ b/basys3/basys3.srcs/top.vhd
@@ -8,7 +8,7 @@ entity top is port (
 	RESET : in std_logic; -- global (async) system reset
 	SPI_CLK : in std_logic; -- incoming clock of SPI 
 	SPI_MOSI : in std_logic; -- incoming data of SPI
-	WEN : in std_logic; -- PPU VRAM write enable
+	SPI_RESET : in std_logic; -- PPU VRAM write enable
 	DBG_DISP_ADDR : in std_logic; -- display address/data switch (debug)
 	DBG_LEDS_OUT : out std_logic_vector(15 downto 0); -- debug address/data output leds
 	R,G,B : out std_logic_vector(PPU_COLOR_OUTPUT_DEPTH-1 downto 0);
@@ -29,29 +29,33 @@ architecture Behavioral of top is
 	end component;
 	component spi port (
 		SYSCLK : in std_logic; -- clock basys3 100MHz
-		SPI_CLK : in std_logic; -- incoming clock of SPI 
-		SPI_MOSI : in std_logic; -- incoming data of SPI
 		RESET : in std_logic; -- async reset
-		DATA : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0)); --  data read
+		DCK : in std_logic; -- data clock (spi format)
+		DI : in std_logic; -- data in (spi format)
+		DO : out std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0) := (others => '0'); --	data out (parallel)
+		WEN : out std_logic); -- write enable (triggers during each word to propagate previous word)
 	end component;
 
+	signal SPI_RST, PPU_WEN : std_logic;
 	signal SPI_DATA : std_logic_vector(PPU_RAM_BUS_ADDR_WIDTH+PPU_RAM_BUS_DATA_WIDTH-1 downto 0);
 	alias SPI_DATA_ADDR is SPI_DATA(31 downto 16);
 	alias SPI_DATA_DATA is SPI_DATA(15 downto 0);
 begin
+	SPI_RST <= RESET or SPI_RESET;
 	serial_peripheral_interface: component spi port map(
 		SYSCLK => SYSCLK,
-		RESET => RESET,
-		SPI_CLK => SPI_CLK,
-		SPI_MOSI => SPI_MOSI,
-		DATA => SPI_DATA);
+		RESET => SPI_RST,
+		DCK => SPI_CLK,
+		DI => SPI_MOSI,
+		DO => SPI_DATA,
+		WEN => PPU_WEN);
 
 	DBG_LEDS_OUT <= SPI_DATA_ADDR when DBG_DISP_ADDR = '1' else SPI_DATA_DATA;
 
 	picture_processing_unit: component ppu port map(
 		CLK100 => SYSCLK,
 		RESET => RESET,
-		WEN => WEN,
+		WEN => PPU_WEN,
 		ADDR => SPI_DATA_ADDR,
 		DATA => SPI_DATA_DATA,
 		R => R,
diff --git a/basys3/basys3.xpr b/basys3/basys3.xpr
index 8645fca..19bbeec 100644
--- a/basys3/basys3.xpr
+++ b/basys3/basys3.xpr
@@ -60,7 +60,7 @@
     <Option Name="IPStaticSourceDir" Val="$PIPUSERFILESDIR/ipstatic"/>
     <Option Name="EnableBDX" Val="FALSE"/>
     <Option Name="DSABoardId" Val="basys3"/>
-    <Option Name="WTXSimLaunchSim" Val="86"/>
+    <Option Name="WTXSimLaunchSim" Val="108"/>
     <Option Name="WTModelSimLaunchSim" Val="0"/>
     <Option Name="WTQuestaLaunchSim" Val="0"/>
     <Option Name="WTIesLaunchSim" Val="0"/>
@@ -235,9 +235,15 @@
           <Attr Name="UsedIn" Val="simulation"/>
         </FileInfo>
       </File>
+      <File Path="$PSRCDIR/ppu_addr_dec_tb.vhd">
+        <FileInfo SFType="VHDL2008">
+          <Attr Name="UsedIn" Val="synthesis"/>
+          <Attr Name="UsedIn" Val="simulation"/>
+        </FileInfo>
+      </File>
       <Config>
         <Option Name="DesignMode" Val="RTL"/>
-        <Option Name="TopModule" Val="ppu_tb"/>
+        <Option Name="TopModule" Val="spi_tb"/>
         <Option Name="TopLib" Val="xil_defaultlib"/>
         <Option Name="TransportPathDelay" Val="0"/>
         <Option Name="TransportIntDelay" Val="0"/>
diff --git a/docs/hardware/pinout.md b/docs/hardware/pinout.md
index a0c11aa..3713087 100644
--- a/docs/hardware/pinout.md
+++ b/docs/hardware/pinout.md
@@ -4,8 +4,7 @@
 |-|-|-|-|-|
 |SPI MOSI|PA7|D11|L2|JA2|
 |SPI CLK|PA5|D13|J2|JA3|
-||
-|PPU VRAM WEN|PA9|D8|J1|JA1|
+|SPI RESET|PA9|D8|J1|JA1|
 ||
 |APU PWM out|||A15|JB7|
 ||
diff --git a/src/main.c b/src/main.c
index bbb6001..658fc94 100644
--- a/src/main.c
+++ b/src/main.c
@@ -6,12 +6,14 @@
 
 bool g_hh_run = true;
 
+bool g_hh_test_complete = false;
+
 void hh_ppu_vblank_interrupt() {
-	for (unsigned long i = 0; i < HH_PPUINTDEMO_LENGTH; i++) {
-		uint16_t addr = HH_PPUINTDEMO_ADDR[i];
-		uint16_t data = HH_PPUINTDEMO_DATA[i];
-		hh_ppu_vram_dwrite(addr, data);
-	}
+#ifdef HH_TARGET_DESKTOP
+	if (g_hh_test_complete) return;
+#endif
+	hh_ppu_vram_dwrite((uint8_t*) HH_PPUINTDEMO_ARR, HH_PPUINTDEMO_LENGTH);
+	g_hh_test_complete = true;
 }
 
 int main() {
diff --git a/src/ppu/consts.h b/src/ppu/consts.h
index a27b7b7..917510f 100644
--- a/src/ppu/consts.h
+++ b/src/ppu/consts.h
@@ -23,6 +23,12 @@
 /** @brief amount of vertical background tiles on background canvas */
 #define HH_PPU_BG_CANVAS_TILES_V 30
 
+/** @brief amount of bytes in command (16 + 16 bits) */
+#define HH_PPU_COMMAND_BYTES 4
+/** @brief command buffer size (large enough to update entire screen + all fg sprites + aux + all palettes) */
+#define HH_PPU_COMMAND_BUFFER_SIZE (HH_PPU_COMMAND_BYTES * \
+		(HH_PPU_VRAM_FAM_SIZE + HH_PPU_VRAM_BAM_SIZE + HH_PPU_VRAM_AUX_SIZE + HH_PPU_VRAM_PAL_SIZE))
+
 #include "ppu/types.h"
 
 /** @brief tilemap memory address offset */
diff --git a/src/ppu/internals.c b/src/ppu/internals.c
index 66c0ac1..a60cb68 100644
--- a/src/ppu/internals.c
+++ b/src/ppu/internals.c
@@ -4,6 +4,9 @@
 #include "ppu/internals.h"
 #include "ppu/types.h"
 
+uint8_t g_hh_ppu_vram_buffer[HH_PPU_COMMAND_BUFFER_SIZE] = { 0 };
+size_t g_hh_ppu_vram_buffer_head = 0;
+
 bool hh_ppu_vram_valid_address(hh_ppu_addr_t addr) {
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wtype-limits"
@@ -17,7 +20,16 @@ bool hh_ppu_vram_valid_address(hh_ppu_addr_t addr) {
 }
 
 void hh_ppu_vram_write(hh_s_ppu_vram_data data) {
-	for (unsigned i = 0; i < data.size; i++) hh_ppu_vram_dwrite(data.offset + i, data.data[i]);
+	for (unsigned i = 0; i < data.size; i++) {
+		hh_ppu_addr_t ppu_addr = data.offset + i;
+		hh_ppu_data_t ppu_data = data.data[i];
+		hh_ppu_vram_buffer((uint8_t[4]) {
+			(ppu_addr >> 8) & 0xff,
+			(ppu_addr >> 0) & 0xff,
+			(ppu_data >> 8) & 0xff,
+			(ppu_data >> 0) & 0xff,
+		});
+	}
 }
 
 hh_s_ppu_vram_data hh_ppu_2nat_bam(hh_s_ppu_loc_bam_entry e) {
@@ -73,3 +85,18 @@ hh_s_ppu_vram_data hh_ppu_2nat_color(hh_ppu_rgb_color_t rgb) {
 	hh_s_ppu_vram_data out = {.data = data, .size = HH_PPU_VRAM_PAL_ENTRY_SIZE};
 	return out;
 }
+
+void hh_ppu_vram_buffer(uint8_t data[4]) {
+	size_t head = g_hh_ppu_vram_buffer_head;
+	g_hh_ppu_vram_buffer[head+0] = data[0];
+	g_hh_ppu_vram_buffer[head+1] = data[1];
+	g_hh_ppu_vram_buffer[head+2] = data[2];
+	g_hh_ppu_vram_buffer[head+3] = data[3];
+	g_hh_ppu_vram_buffer_head += 4;
+}
+
+void hh_ppu_vram_flush() {
+	hh_ppu_vram_dwrite(g_hh_ppu_vram_buffer, g_hh_ppu_vram_buffer_head);
+	g_hh_ppu_vram_buffer_head = 0;
+}
+
diff --git a/src/ppu/internals.h b/src/ppu/internals.h
index 4a1726e..12c556e 100644
--- a/src/ppu/internals.h
+++ b/src/ppu/internals.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <stdbool.h>
+#include <stdlib.h>
 
 #include "ppu/types.h"
 
@@ -18,11 +19,16 @@ typedef struct {
 
 /** @brief check if `addr` is a valid PPU address */
 bool hh_ppu_vram_valid_address(hh_ppu_addr_t addr);
-/** @brief direct write vram word (platform-specific implementation) */
-void hh_ppu_vram_dwrite(hh_ppu_addr_t addr, hh_ppu_data_t data);
 /** @brief write data block into vram */
 void hh_ppu_vram_write(hh_s_ppu_vram_data data);
 
+/** @brief add raw SPI data to ppu command buffer */
+void hh_ppu_vram_buffer(uint8_t data[4]);
+/** @brief propagate command buffer (also handles SPI reset) */
+void hh_ppu_vram_flush();
+/** @brief write raw spi bytes in ppu format */
+void hh_ppu_vram_dwrite(uint8_t* data, size_t size);
+
 /** @brief convert local background attribute memory entry to PPU format */
 hh_s_ppu_vram_data hh_ppu_2nat_bam(hh_s_ppu_loc_bam_entry);
 /** @brief convert local foreground attribute memory entry to PPU format */
diff --git a/src/ppu/stm.c b/src/ppu/stm.c
index 371e557..18811cf 100644
--- a/src/ppu/stm.c
+++ b/src/ppu/stm.c
@@ -7,17 +7,10 @@
 void hh_ppu_init() {}
 void hh_ppu_deinit() {}
 
-void hh_ppu_vram_dwrite(hh_ppu_addr_t addr, hh_ppu_data_t data) {
-	// if (!hh_ppu_vram_valid_address(addr)) return;
-
-	uint8_t spi_data[4] = {
-		(addr & 0xff00) >> 8,
-		(addr & 0x00ff) >> 0,
-		(data & 0xff00) >> 8,
-		(data & 0x00ff) >> 0,
-	};
-
-	HAL_SPI_Transmit(&hspi1, spi_data, 4, HAL_MAX_DELAY);
+void hh_ppu_vram_dwrite(uint8_t* data, size_t size) {
+	HAL_SPI_Transmit(&hspi1, data, size, HAL_MAX_DELAY);
+	HAL_SPI_Transmit(&hspi1, (uint8_t[4]) { 0xff, 0xff, 0xff, 0xff }, 4, HAL_MAX_DELAY);
 	HAL_GPIO_WritePin(GPIOA, GPIO_PIN_9, true);
 	HAL_GPIO_WritePin(GPIOA, GPIO_PIN_9, false);
 }
+
diff --git a/src/ppusim/mem.c b/src/ppusim/mem.c
index bd8606e..f536727 100644
--- a/src/ppusim/mem.c
+++ b/src/ppusim/mem.c
@@ -6,8 +6,14 @@
 
 hh_ppu_data_t *g_hh_ppusim_vram = NULL;
 
-void hh_ppu_vram_dwrite(hh_ppu_addr_t addr, hh_ppu_data_t data) {
-	if (!hh_ppu_vram_valid_address(addr)) return;
-	// printf("ppu[0x%04x] = %04x\n", addr, data);
-	g_hh_ppusim_vram[addr] = data;
+void hh_ppu_vram_dwrite(uint8_t* data, size_t size) {
+	for (size_t i = 0; i < size; i += 4) {
+		if (i+4 > size) break;
+		hh_ppu_addr_t ppu_addr = (data[i+0] << 8) | (data[i+1] << 0);
+		hh_ppu_data_t ppu_data = (data[i+2] << 8) | (data[i+3] << 0);
+		// printf("%04x: %04x\n", ppu_addr, ppu_data);
+		if (!hh_ppu_vram_valid_address(ppu_addr)) continue;
+		g_hh_ppusim_vram[ppu_addr] = ppu_data;
+	}
 }
+
diff --git a/src/stm32/main.c b/src/stm32/main.c
index 84288c3..d815154 100644
--- a/src/stm32/main.c
+++ b/src/stm32/main.c
@@ -6,6 +6,8 @@
 void hh_ppu_load_tilemap() {}
 
 void hh_loop() {
-	HAL_Delay(1e3);
-	hh_ppu_vblank_interrupt();
+	while (1) {
+		hh_ppu_vblank_interrupt();
+		HAL_Delay(1e3);
+	}
 }
diff --git a/test/ppu-stm-integration-demo/data2test.awk b/test/ppu-stm-integration-demo/data2test.awk
new file mode 100755
index 0000000..286a388
--- /dev/null
+++ b/test/ppu-stm-integration-demo/data2test.awk
@@ -0,0 +1,15 @@
+#!/bin/awk -f
+BEGIN {
+	print "#pragma once"
+	print "#include <stdint.h>"
+	printf("const uint8_t HH_PPUINTDEMO_ARR[] = { ")
+}
+
+length($1) == 4 && length($2) == 4 {
+	printf "0x"substr($1,1,2)", 0x"substr($1,3,2)", 0x"substr($2,1,2)", 0x"substr($2,3,2)", "
+}
+
+END {
+	printf("};\n") # close array
+	printf("#define HH_PPUINTDEMO_LENGTH %d\n", NR*4) # calculate array length
+}
diff --git a/test/ppu-stm-integration-demo/makefile b/test/ppu-stm-integration-demo/makefile
index 7d7a7c8..2f4b6f4 100644
--- a/test/ppu-stm-integration-demo/makefile
+++ b/test/ppu-stm-integration-demo/makefile
@@ -4,12 +4,8 @@ TARGETS := test-background-color.h test-image.h test-image.tb.vhd
 
 all: $(TARGETS)
 
-%.h: %.txt
-	echo "#pragma once" > $@
-	echo "#include <stdint.h>" >> $@
-	(printf "#define HH_PPUINTDEMO_LENGTH "; wc -l < $<) >> $@
-	tr -d ':' < $< | awk 'BEGIN { printf "const uint16_t HH_PPUINTDEMO_ADDR[] = { " } 1 { printf "0x"$$1", " } END { print "};" }' >> $@
-	tr -d ':' < $< | awk 'BEGIN { printf "const uint16_t HH_PPUINTDEMO_DATA[] = { " } 1 { printf "0x"$$2", " } END { print "};" }' >> $@
+%.h: %.txt ./data2test.awk
+	tr -d ':' < $< | ./data2test.awk > $@
 
 test-%.tb.vhd: test-%.txt ./data2vhdltb.awk
 	tr -d ':' < $< | ./data2vhdltb.awk > $@
-- 
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