First version

firmware/main.c

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+/**
+ * \file main.c
+ * \brief Firmware for the USB-Servo
+ * \author Ronald Schaten
+ * \version $Id: main.c,v 1.1 2006/10/28 12:40:42 rschaten Exp $
+ *
+ * License: See documentation.
+ */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/pgmspace.h>
+#include <util/delay.h>
+
+#include "usbdrv.h"
+#include "oddebug.h"
+#include "usbservo.h"
+
+/** Global variable, contains the angle of the servo. */
+static uint8_t angle;
+
+/**
+ * Handler for the timer-interrupt. This function is called every 20
+ * milliseconds (50Hz).
+ */
+static void timerInterrupt(void) {
+    int i;
+    PORTC = 0xff;
+    // wait 7200us (value by trial & error)
+    for (i = 0; i < 72; i++) {
+        _delay_us(100);
+    }
+    // still have to wait up to 17850us (value by trial & error)
+    for (i = 0; i < angle; i++) {
+        _delay_us(70);          // 17850 / 255 = 70
+    }
+    PORTC = 0x00;
+}
+
+/**
+ * USB-Setup-Handler. Handles setup-calls that are received from the
+ * USB-Interface.
+ * \param data Eight bytes of data.
+ * \return The number of returned bytes (in replyBuffer[]).
+ */
+uchar usbFunctionSetup(uchar data[8]) {
+    static uchar replyBuffer[8];
+    uchar replyLength;
+
+    replyBuffer[0] = msgOK;
+    switch (data[1]) {
+    case CMD_ECHO:             /* echo */
+        replyBuffer[0] = data[2];
+        replyBuffer[1] = data[3];
+        replyLength = 2;
+        break;
+    case CMD_GET:              /* read status */
+        replyBuffer[0] = angle;
+        replyLength = 1;
+        break;
+    case CMD_SET:              /* set status */
+        angle = data[2];
+        replyLength = 0;
+        break;
+    default:                   /* WTF? */
+        replyBuffer[0] = msgErr;
+        replyLength = 1;
+        break;
+    }
+    usbMsgPtr = replyBuffer;
+    return replyLength;
+}
+
+/**
+ * Main-function. Initializes the hardware and starts the main loop of the
+ * application.
+ * \return An integer. Whatever... :-)
+ */
+int main(void) {
+    uchar i, j;
+    odDebugInit();
+    DDRD = ~0;                  /* output SE0 for USB reset */
+    PORTD = 0x00;               /* no pullups on USB pins */
+    DDRC = 0xff;                /* all outputs */
+    PORTC = 0x00;
+
+    j = 0;
+    while (--j) {               /* USB Reset by device only required on
+                                   Watchdog Reset */
+        i = 0;
+        while (--i);            /* delay >10ms for USB reset */
+    }
+    DDRD = ~USBMASK;            /* all outputs except USB data */
+    TCCR0 = 5;                  /* set prescaler to 1/1024 */
+    usbInit();
+    sei();
+
+    for (i = 0; i < 10; i++) {  /* wait one second to prevent strange
+                                   effects when the USB-bus isn't
+                                   initialized (e. g. when the host system
+                                   is on standby. */
+        _delay_ms(100);
+    }
+
+    angle = 0;
+
+    while (1) {                 /* main event loop */
+        usbPoll();
+        if (TIFR & (1 << TOV0)) {
+            TIFR |= 1 << TOV0;  /* clear pending flag */
+            timerInterrupt();
+        }
+    }
+    return 0;
+}