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-rw-r--r--examples/vga-scope.cpp212
1 files changed, 134 insertions, 78 deletions
diff --git a/examples/vga-scope.cpp b/examples/vga-scope.cpp
index 0265f9c..9c6dca5 100644
--- a/examples/vga-scope.cpp
+++ b/examples/vga-scope.cpp
@@ -1,34 +1,90 @@
-// Low-level, non-wirish demonstration of VGA
-//
-// Connect a microphone or something less to ANALOG_PIN
+/*
+ VGA Oscilloscope demo.
+
+ Connect a microphone or something like it to ANALOG_PIN (0V -- 3.3V
+ only; 0.2V -- 3.1V will probably look nicer); an attached VGA
+ monitor will display the signal roughly in real-time.
+
+ The thick blue line corresponds roughly to 0V.
+
+ This is a fairy crude hack, but it's fun to watch/toy around with.
+
+ SerialUSB and SysTick are disabled to get rid of the most frequently
+ occurring interrupts (which mess with timing). This means that you
+ have to use perpetual bootloader mode or the reset button to flash
+ new programs.
+
+ How to wire this to a VGA port:
+ D6 via ~200ohms to VGA Red (1)
+ D7 via ~200ohms to VGA Green (2)
+ D8 via ~200ohms to VGA Blue (3)
+ D11 to VGA VSync (14) (swapped?)
+ D12 to VGA HSync (13) (swapped?)
+ GND to VGA Ground (5)
+ GND to VGA Sync Ground (10)
+
+ See also:
+ - http://pinouts.ru/Video/VGA15_pinout.shtml
+ - http://www.epanorama.net/documents/pc/vga_timing.html
+
+ This code is released into the public domain.
+ */
#include "wirish.h"
+#include "systick.h"
+
+// FIXME generalize for Native and Mini
-#define LED_PIN 13
+#define LED_PIN BOARD_LED_PIN
#define ANALOG_PIN 18
-#define VGA_R 5 // B6
-#define VGA_G 6 // A8
-#define VGA_B 7 // A9
-#define VGA_V 11 // A6
-#define VGA_H 12 // A7
-#define VGA_R_HIGH (GPIOB_BASE)->BSRR = BIT(6)
-#define VGA_R_LOW (GPIOB_BASE)->BRR = BIT(6)
-#define VGA_G_HIGH (GPIOA_BASE)->BSRR = BIT(8)
-#define VGA_G_LOW (GPIOA_BASE)->BRR = BIT(8)
-#define VGA_B_HIGH (GPIOA_BASE)->BSRR = BIT(9)
-#define VGA_B_LOW (GPIOA_BASE)->BRR = BIT(9)
-#define VGA_V_HIGH (GPIOA_BASE)->BSRR = BIT(6)
-#define VGA_V_LOW (GPIOA_BASE)->BRR = BIT(6)
-#define VGA_H_HIGH (GPIOA_BASE)->BSRR = BIT(7)
-#define VGA_H_LOW (GPIOA_BASE)->BRR = BIT(7)
+
+// Pinouts -- you also must change the GPIO macros below if you change
+// these
+#define VGA_R 6 // STM32: A8
+#define VGA_G 7 // STM32: A9
+#define VGA_B 8 // STM32: A10
+#define VGA_V 11 // STM32: A6
+#define VGA_H 12 // STM32: A7
+
+// These low level (and STM32 specific) macros make GPIO writes much
+// faster
+#define ABSRR ((volatile uint32*)0x40010810)
+#define ABRR ((volatile uint32*)0x40010814)
+
+#define RBIT 8 // (see pinouts)
+#define GBIT 9
+#define BBIT 10
+
+#define VGA_R_HIGH *ABSRR = BIT(RBIT)
+#define VGA_R_LOW *ABRR = BIT(RBIT)
+#define VGA_G_HIGH *ABSRR = BIT(GBIT)
+#define VGA_G_LOW *ABRR = BIT(GBIT)
+#define VGA_B_HIGH *ABSRR = BIT(BBIT)
+#define VGA_B_LOW *ABRR = BIT(BBIT)
+
+#define COLOR_WHITE (BIT(RBIT) | BIT(GBIT) | BIT(BBIT))
+#define COLOR_BLACK 0
+#define COLOR_RED BIT(RBIT)
+#define COLOR_GREEN BIT(GBIT)
+#define COLOR_BLUE BIT(BBIT)
+
+#define BORDER_COLOR COLOR_BLUE
+
+// set has priority, so clear every bit and set some given bits:
+#define VGA_COLOR(c) (*ABSRR = c | \
+ BIT(RBIT+16) | BIT(GBIT+16) | BIT(BBIT+16))
+
+#define VGA_V_HIGH *ABSRR = BIT(6)
+#define VGA_V_LOW *ABRR = BIT(6)
+#define VGA_H_HIGH *ABSRR = BIT(7)
+#define VGA_H_LOW *ABRR = BIT(7)
void isr_porch(void);
void isr_start(void);
void isr_stop(void);
void isr_update(void);
-void setup()
-{
+void setup() {
pinMode(LED_PIN, OUTPUT);
pinMode(ANALOG_PIN, INPUT_ANALOG);
digitalWrite(LED_PIN, 1);
@@ -38,104 +94,104 @@ void setup()
pinMode(VGA_V, OUTPUT);
pinMode(VGA_H, OUTPUT);
- /* Send a message out USART2 */
+ // Send a message out USART2
Serial2.begin(9600);
- Serial2.println("Video time...");
+ Serial2.println("Time to kill the radio star...");
// This gets rid of the majority of the interrupt artifacts;
- // a SysTick.end() is required as well
+ // there's still a glitch for low values of y, but let's not worry
+ // about that. (Probably due to the hackish way vsync is done).
SerialUSB.end();
-
+ systick_disable();
+
digitalWrite(VGA_R, 0);
digitalWrite(VGA_G, 0);
digitalWrite(VGA_B, 0);
- digitalWrite(VGA_H,1);
- digitalWrite(VGA_V,1);
-
- timer_set_prescaler(4,0);
- timer_set_mode(4, 1, TIMER_OUTPUTCOMPARE);
- timer_set_mode(4, 2, TIMER_OUTPUTCOMPARE);
- timer_set_mode(4, 3, TIMER_OUTPUTCOMPARE);
- timer_set_mode(4, 4, TIMER_OUTPUTCOMPARE);
- timer_set_reload(4, 2287);
- timer_set_compare_value(4,1,200);
- timer_set_compare_value(4,2,300);
- timer_set_compare_value(4,3,2170); // 2219 max...
- timer_set_compare_value(4,4,1);
- timer_attach_interrupt(4,1,isr_porch);
- timer_attach_interrupt(4,2,isr_start);
- timer_attach_interrupt(4,3,isr_stop);
- timer_attach_interrupt(4,4,isr_update);
-
- timer_set_count(4,0);
+ digitalWrite(VGA_H, 1);
+ digitalWrite(VGA_V, 1);
+
+ timer_pause(TIMER4);
+ timer_set_prescaler(TIMER4, 0);
+ timer_set_mode(TIMER4, 1, TIMER_OUTPUTCOMPARE);
+ timer_set_mode(TIMER4, 2, TIMER_OUTPUTCOMPARE);
+ timer_set_mode(TIMER4, 3, TIMER_OUTPUTCOMPARE);
+ timer_set_mode(TIMER4, 4, TIMER_OUTPUTCOMPARE);
+ timer_set_reload(TIMER4, 2287);
+ timer_set_compare_value(TIMER4, 1, 200);
+ timer_set_compare_value(TIMER4, 2, 250);
+ timer_set_compare_value(TIMER4, 3, 2170); // 2219 max...
+ timer_set_compare_value(TIMER4, 4, 1);
+ timer_attach_interrupt(TIMER4, 1, isr_porch);
+ timer_attach_interrupt(TIMER4, 2, isr_start);
+ timer_attach_interrupt(TIMER4, 3, isr_stop);
+ timer_attach_interrupt(TIMER4, 4, isr_update);
+
+ timer_set_count(TIMER4, 0);
+ timer_resume(TIMER4);
}
-int toggle = 0;
-uint16 x = 0;
uint16 y = 0;
uint16 val = 0;
-uint8 v_active = 1;
-GPIO_Port *portb = GPIOB_BASE;
+bool v_active = true;
+const uint16 x_max = 60; // empirically (and lazily) determined
void isr_porch(void) {
VGA_H_HIGH;
y++;
- if(y>=523) {
- y=1;
- v_active = 1;
+ val = map(analogRead(ANALOG_PIN), 0, 4095, 0, x_max);
+ if(y >= 523) {
+ y = 1;
+ v_active = true;
return;
}
- if(y>=492) {
+ if(y >= 492) {
VGA_V_HIGH;
return;
}
- if(y>=490) {
+ if(y >= 490) {
VGA_V_LOW;
return;
}
- if(y>=479) { // 479
- v_active = 0;
+ if(y >= 479) {
+ v_active = false;
return;
}
}
void isr_start(void) {
- if(!v_active) { return; }
- VGA_R_HIGH;
- VGA_R_HIGH;
- VGA_R_HIGH;
- VGA_R_LOW;
- //delayMicroseconds(2);
- //gpio_write_bit(GPIOA_BASE, 8, 1); // VGA_G
- for(x=0; x<(val>>6); x++) {
- }
- VGA_B_HIGH;
- VGA_G_HIGH;
- VGA_G_LOW;
- VGA_B_LOW;
- //VGA_R_HIGH;
- //val = (val + analogRead(ANALOG_PIN))/2;
- val = analogRead(ANALOG_PIN);
-
+ if (!v_active) {
+ return;
+ }
+ VGA_COLOR(BORDER_COLOR);
+ for (int x = 0; x < val; x++) {
+ VGA_COLOR(COLOR_BLACK);
+ }
+ VGA_COLOR(COLOR_WHITE);
+ VGA_COLOR(COLOR_BLACK);
}
+
void isr_stop(void) {
- if(!v_active) { return; }
- VGA_R_LOW;
- VGA_G_LOW;
- VGA_B_LOW;
+ if (!v_active) {
+ return;
+ }
+ VGA_COLOR(COLOR_BLACK);
}
+
void isr_update(void) {
VGA_H_LOW;
}
void loop() {
- //val = analogRead(ANALOG_PIN);
+ toggleLED();
+ delay(100);
}
+__attribute__((constructor)) void premain() {
+ init();
+}
int main(void) {
- init();
setup();
while (1) {
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