Convert SNES polling to a timer interrupt-based routine, update comments.

diff --git a/main.c b/main.c
index 6a8ff6bb731d99e25d99448faa2c38d24d837aa3..236766cdc62d198a26d930529ad4ff105ea34677 100644 (file)
--- a/main.c
+++ b/main.c
@@ -27,11 +27,16 @@ PROGMEM char usbHidReportDescriptor[28] = {
        0xc0,        //   END_COLLECTION
        0xc0         // END_COLLECTION
 };
-
+/*
 typedef struct {
        uchar buttons[2];
 } report_t;
+*/
+typedef struct {
+       uint16_t buttons;
+} report_t;
 
+static report_t buttonState;
 static report_t reportBuffer;
 
 usbMsgLen_t usbFunctionSetup(uchar data[8]) {
@@ -53,10 +58,31 @@ usbMsgLen_t usbFunctionSetup(uchar data[8]) {
        return 0;   /* default for not implemented requests: return no data back to host */
 }
 
+ISR(TIMER1_COMPA) {
+       buttonState.buttons = pollSnes();
+}
+
+void initTimer() {
+       // See section 15.11 for reference
+       // Using CTC mode (non-PWM)
+
+       // TCCR1A = 0b00000000 (No timer output, no PWM)
+       // TCCR1B = 0b00001010 (CTC mode, ckli_o/8)
+       // TCCR1C = 0b00000000 (No output compare)
+       TCCR1A = 0b00000000;
+       TCCR1B = 0b00001010;
+       TCCR1C = 0b00000000;
+       // {OCR1AH, OCR1AL} = 37500 = 10010010 01111100
+       // 37500 * 8 * 60 = 18MHz
+       OCR1AH = 0b10010010;
+       OCR1AL = 0b01111000;
+       // TIMSK1 = 0b00000010 (Enable interrupt on Output Compare A Match)
+       TIMSK1 = 0b00000010;
+}
+
 int main(void)
 {
        uchar i;
-
        wdt_enable(WDTO_1S); // Enable watchdog with 1s reset time
        /* Even if you don't use the watchdog, turn it off here. On newer devices,
         * the status of the watchdog (on/off, period) is PRESERVED OVER RESET!
@@ -66,9 +92,18 @@ int main(void)
        
        /* RESET status: all port bits are inputs without pull-up.
         * That's the way we need D+ and D-. Therefore we don't need any
-        * additional hardware initialization.
+        * additional hardware initialization on the USB side.
         */
        
+       // We need to setup the pin configuration for D3, which is an output pin 
+       
+
+       // Set up the clock prescaler to CLKI_O/8, which gives us 2250000 ticks per second
+       // This makes 37500 such ticks give us a 60Hz signal, which is exactly how we set up
+       // the timer interrupt to poll the SNES controller
+       
+
+
        //odDebugInit();
        
        usbInit();
@@ -86,7 +121,7 @@ int main(void)
                wdt_reset();
                usbPoll();
                if(usbInterruptIsReady()){
-                       pollSnes();
+                       reportBuffer.buttons = buttonState.buttons;
                        /* called after every poll of the interrupt endpoint */
                        //advanceCircleByFixedAngle();
                        //DBG1(0x03, 0, 0);   /* debug output: interrupt report prepared */

diff --git a/snes.S b/snes.S
index 02e385beb493754c5ad3121316a597eea2add832..bac54a00c5e2d59295c2d6a27d6258dc2a3513d5 100644 (file)
--- a/snes.S
+++ b/snes.S
@@ -153,8 +153,8 @@ readbitsecond8:
 
 invertvalues:
        ldi temp2, 0xff ; for xor
-       eor resL, temp2 ; Invert for negative logic
-       eor resH, temp2 ; Remember, low indicates button pressed.
+       eor resL, temp2 ; Invert for negative logic - to the SNES controller,
+       eor resH, temp2 ; low indicates button pressed.  To USB HID, the opposite.
        ret             ; return to caller
 
 unconnected:           ; Controller was disconnected