# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1540325660 -7200
# Node ID 424c116cadb1a7ee128dd8910c32384feb44da6b
# Parent  2e21b707dbdae33698d42917bd910798f27d98f3
Introduced framebuffer usage and replaced the DMA interrupt with a Timer2 event,
making the vga-pmp example consistent with the others.

diff -r 2e21b707dbda -r 424c116cadb1 examples/vga-pmp/main.c
--- a/examples/vga-pmp/main.c	Tue Oct 23 22:11:05 2018 +0200
+++ b/examples/vga-pmp/main.c	Tue Oct 23 22:14:20 2018 +0200
@@ -27,6 +27,7 @@
 #include "main.h"
 #include "devconfig.h"
 #include "vga.h"
+#include "display.h"
 
 
 
@@ -35,20 +36,16 @@
 static void (*state_handler)(void);
 static uint32_t line;
 
+/* Pointers to pixel lines. */
+
+static uint8_t *linedata, *linedatalimit, *screenstart;
+
 /* Pixel data. */
 
-static uint8_t linedata[LINE_LENGTH];
 static const uint8_t zerodata[ZERO_LENGTH] = {0};
-
+static uint8_t framebuffer[SCREEN_SIZE];
 
 
-static void test_linedata(void)
-{
-    int i;
-
-    for (i = 0; i < LINE_LENGTH; i++)
-        linedata[i] = (i % 2) ? 0xff : 0x00;
-}
 
 /* Blink an attached LED with delays implemented using a loop. */
 
@@ -69,8 +66,6 @@
         /* Invert outputs (LED). */
 
         INV_REG(port, pins);
-        rbits(PM_REG(0, PMxCON)); uart_write_nl();
-        rhex(PM_REG(0, PMxMODE)); uart_write_nl();
     }
 }
 
@@ -82,7 +77,12 @@
 {
     line = 0;
     state_handler = vbp_active;
-    test_linedata();
+    test_linedata(framebuffer);
+
+    /* Initialise the current display line pointer and display limit. */
+
+    linedatalimit = framebuffer + SCREEN_SIZE;
+    screenstart = framebuffer;
 
     init_memory();
     init_pins();
@@ -112,16 +112,15 @@
     dma_set_transfer(0, PHYSICAL((uint32_t) linedata), LINE_LENGTH,
                         HW_PHYSICAL(PM_REG(0, PMxDIN)), 1,
                         TRANSFER_CELL_SIZE);
-    dma_init_interrupt(0, 0b1000, 1, 3);
 
-    /* Enable DMA on the preceding channel's completion, with this also
-       initiating transfers. This "reset" or "zero" transfer is employed to set
-       the pixel level to black in a connected flip-flop. Without the flip-flop
-       it is superfluous. */
+    /* Enable DMA on the preceding channel's completion, with the timer event
+       initiating the transfer. This "reset" or "zero" transfer is employed to
+       set the pixel level to black in a connected flip-flop. Without the
+       flip-flop it is superfluous. */
 
     dma_init(1, 3);
     dma_set_chaining(1, dma_chain_previous);
-    dma_set_interrupt(1, DMA0, 1);
+    dma_set_interrupt(1, T2, 1);
     dma_set_transfer(1, PHYSICAL((uint32_t) zerodata), ZERO_LENGTH,
                         HW_PHYSICAL(PM_REG(0, PMxDIN)), 1,
                         ZERO_LENGTH);
@@ -200,7 +199,10 @@
 
     state_handler = visible_active;
 
-    /* NOTE: Set the line address. */
+    /* Set the line address. */
+
+    linedata = screenstart;
+    dma_set_source(0, PHYSICAL((uint32_t) linedata), LINE_LENGTH);
 
     /* Enable the channel for the next line. */
 
@@ -211,22 +213,18 @@
 
 void visible_active(void)
 {
-    uint32_t ifs;
-
-    /* Remove any DMA interrupt condition (CHBCIF). */
-
-    ifs = REG(DMAIFS) & DMA_INT_FLAGS(0, DCHxIF);
-
-    if (ifs)
-    {
-        CLR_REG(DMA_REG(0, DCHxINT), 0b11111111);
-        CLR_REG(DMAIFS, ifs);
-    }
-
     if (line < VFP_START)
     {
-        /* NOTE: Update the line address and handle wraparound. */
+        /* Update the line address and handle wraparound. */
 
+        if (!(line % LINE_MULTIPLIER))
+        {
+            linedata += LINE_LENGTH;
+            if (linedata >= linedatalimit)
+                linedata -= SCREEN_SIZE;
+        }
+
+        dma_set_source(0, PHYSICAL((uint32_t) linedata), LINE_LENGTH);
         return;
     }