Works: measures time and client displays a primitive stripchart.

1 files changed, 53 insertions, 19 deletions

diff --git a/example.c b/example.c
index 129b6eb..7409fdf 100644
--- a/example.c
+++ b/example.c
@@ -36,38 +36,55 @@ void send_str(const char *s);
 uint8_t recv_str(char *buf, uint8_t size);
 void parse_and_execute_command(const char *buf, uint8_t num);
 
-// Very simple character echo test
 int main(void)
 {
-	int changed = 0;
+	int changed = 0, val;
 	int port = 'B' - 'A';
-	int pin = '0' - '0';
-	int val;
-	CPU_PRESCALE(0);
+	int pin = 1 << ('0' - '0');
+	int latency = 0;
+
+	CPU_PRESCALE(0x00); // 16 MHz
 	usb_init();
 	LED_CONFIG;
 	while (!usb_configured()) /* wait */ ;
 	_delay_ms(1000);
-
-	LED_ON;
-
+	CPU_PRESCALE(0x04); // 1 MHz
 
 	uint8_t *portload = 0x20 + port * 3;
+	*portload &= ~pin;
 
-	*(uint8_t *)(0x21 + port * 3) &= ~(1 << pin);
-
+	TCCR1B |= (1 << CS10); // Set timer1 to 1 microsecond steps
 
 	while (1) {
-		val = *portload & (1 << pin);
-//		usb_serial_putchar(val + '0');
-		if ((val == 1)  && (changed == 0)) {
-			changed = 1;
-			usb_serial_putchar(val ? '1' : '0');
-			LED_ON;
-		} else if ((val == 0)  && (changed == 1)) {
+		val = *portload & pin;
+		if ((val == 0)  && (changed == 1)) {
+			/* trailing edge of pulse.
+			 *
+			 * I track the 1->0 transition rather than
+			 * 0->1 because it's sharper.
+			 */
+			int count;
+			count = TCNT1; // read timer
+			if (count < 15000)
+				/* ignore spurious pulses.  If I don't
+				 * do this, for some reason I'll see a
+				 * bunch of half-width pulses.
+				 */
+				continue;
+			TCNT1 = 0; // reset timer
 			changed = 0;
-			usb_serial_putchar(val ? '1' : '0');
-			LED_OFF;
+
+//			usb_serial_putchar(count > 16667 ? '>' : '<');
+			send_int(count);
+			usb_serial_putchar(' ');
+			send_int(latency);
+			usb_serial_putchar('\n');
+			latency = TCNT1;
+		} else if ((val == 1)  && (changed == 0)) {
+			/* leading edge of pulse.
+			 */
+			changed = 1;
+//			usb_serial_putchar('0');
 		}
 	}
 }
@@ -85,6 +102,23 @@ void send_str(const char *s)
 	}
 }
 
+/* Write a decimal integer to the serial port
+ */
+void send_int(int val)
+{
+	char c_out[10];
+	int ptr;
+	c_out[ptr++] = '\0';
+	while (val > 0) {
+		c_out[ptr++] = (val % 10) + '0';
+		val /= 10;
+	}
+	ptr--;
+	while (ptr) {
+		usb_serial_putchar(c_out[ptr--]);
+	}
+}
+
 // Receive a string from the USB serial port.  The string is stored
 // in the buffer and this function will not exceed the buffer size.
 // A carriage return or newline completes the string, and is not