Rx works!

USBCAS/fmrx.c

@@ -6,8 +6,38 @@
 
 static uint16_t one_bit_lo, one_bit_hi; /* Range for an edge being a "1" */
 
+static inline void fmrx_led_on(void)
+{
+	PORTB &= ~(1 << 0);
+}
+
+static inline void fmrx_led_off(void)
+{
+	PORTB |= (1 << 0);
+}
+
+static void say(const char *str)
+{
+#if 0
+	char c;
+
+	while ((c = *str++))
+		fmrx_recv_byte(c);
+#endif
+}
+
 void fmrx_init(void)
 {
+	uint8_t tccr1b;
+
+	/* ICP1/PD4 is input, with pullup */
+	DDRD  &= ~(1 << 4);
+	PORTD |=  (1 << 4);
+
+	/* PB0 is RXLED */
+	DDRB |= (1 << 0);
+	fmrx_led_off();
+
 	/* Stop counter */
 	TCCR1B = 0;
 
@@ -20,25 +50,36 @@ void fmrx_init(void)
 	/* Clear timer counter */
 	TCNT1 = 0;
 
-	/* Input capture noise canceler on, no prescaler, normal mode;
+	/*
+	 * Input capture noise canceler on, no prescaler, normal mode;
 	 * start timer
 	 */
-	TCCR1B = (1 << ICNC1) + (1 << CS10);
+	tccr1b = (1 << ICNC1) + (1 << CS10);
+	if (!(PIND & (1 << 4)))
+		tccr1b |= 1 << ICES1;
+	TCCR1B = tccr1b;
 }
 
 static uint16_t bytes;
 
 void fmrx_set_speed(uint32_t baudrate)
 {
+	char msg[256];
+
 	one_bit_lo = F_CPU / (4 * baudrate);
 	one_bit_hi = 3 * one_bit_lo;
 
 	bytes = 0;
+	sprintf(msg, "\r\nbaudrate   = %lu\r\n"
+		"one_bit_lo = %u\r\n"
+		"one_bit_hi = %u\r\n",
+		baudrate, one_bit_lo, one_bit_hi);
+	say(msg);
 }
 
 /* We "hunt" for a block until we find this bit pattern; same as ABC800 */
-#define CAS_SYNC_PATTERN 0x0216
-#define CAS_BLOCK_LEN    (1+1+2+253+1+2) /* STX+type+num+data+ETX+checksum */
+#define CAS_SYNC_PATTERN 0x0216 /* SYNC + STX */
+#define CAS_BLOCK_LEN    (1+2+253+1+2) /* type+num+data+ETX+checksum */
 
 /* Interrupt routine for edge capture */
 ISR(TIMER1_CAPT_vect)
@@ -46,6 +87,7 @@ ISR(TIMER1_CAPT_vect)
 	static uint16_t last_edge;
 	static uint16_t data;
 	static uint8_t  bits;
+	char tbuf[16];
 
 	uint16_t edge, delta;
 
@@ -53,27 +95,42 @@ ISR(TIMER1_CAPT_vect)
 	edge = ICR1;
 
 	delta = edge - last_edge;
-	last_edge = edge;
 
 	if (delta < one_bit_lo) {
 		/* Early edge, no action */
+		say("E");
 		return;
 	} else if (delta < one_bit_hi) {
+		say("D");
 		/* A data bit edge */
-		data |= 1;
+		data |= (1 << 15);
 	} else {
+		say("C");
 		/* Clock edge */
+		last_edge = edge;
 		if (bytes) {
 			if (--bits == 0) {
-				fmrx_recv_byte(data);
+				uint8_t outbyte = data >> 8;
+				sprintf(tbuf, "<%02x>", outbyte);
+				say(tbuf);
+				fmrx_recv_byte(outbyte);
 				data = 0; /* To avoid false sync */
 				bits = 8;
-				bytes--;
+				if (--bytes == 0)
+					fmrx_led_off();
+			}
+		} else {
+			sprintf(tbuf, "[%04x]", data);
+			say(tbuf);
+
+			if (data == CAS_SYNC_PATTERN) {
+				bits = 8;
+				bytes = CAS_BLOCK_LEN;
+				fmrx_led_on();
 			}
-		} else if (data == CAS_SYNC_PATTERN) {
-			bits = 8;
-			bytes = CAS_BLOCK_LEN;
 		}
-		data <<= 1;
+		data >>= 1;
 	}
+	sprintf(tbuf, "%u ", delta);
+	say(tbuf);
 }

USBCAS/fmtx.c

@@ -1,6 +1,6 @@
 /*
  * Transmit an FM-modulated signal using the USART in SPI master mode.
- * As per ABC standard, this signal is transmitted LSB first.
+ * As per ABC standard, this signal is transmitted MSB first.
  */
 
 #include "usbcas.h"
@@ -35,7 +35,7 @@ uint8_t fmtx_send_more(void)
 
 	UCSR1A = (1 << TXC1);
 	UDR1 = pattern;
-	data = d >> BITS_PER_PATTERN_BYTE;
+	data >>= BITS_PER_PATTERN_BYTE;
 	left -= BITS_PER_PATTERN_BYTE;
 	parity = -((int8_t)pattern < 0);
 	return left;
@@ -89,7 +89,7 @@ void fmtx_init_speed(uint32_t baudrate)
 	ubrrval = FMTX_UBRRVAL(baudrate);
 
 	DDRD |= 0x28; /* PD3 = outdata, PD5 = XCK/TXLED */
-	PORTD = (PORTD & ~0x28) | (parity & 0x20) | 0x08;
+	PORTD = (PORTD & ~0x28) | 0x20 | (parity & 0x08);
 
 	UCSR1B = 0;	/* Disable USART */
 	UCSR1A = 0;	/* Clear error bits */

USBCAS/usbcas.c

@@ -97,10 +97,12 @@ static void update_modem_status(USB_ClassInfo_CDC_Device_t* const CDCInterfaceIn
 	if (!(PINB & (1 << 4))) /* Cassette relay active */
 		lines |= CDC_CONTROL_LINE_IN_DCD;
 
+#if 0
 	if (lines & CDC_CONTROL_LINE_IN_DCD)
 		PORTB &= ~(1U << 0);
 	else
 		PORTB |= (1U << 0);
+#endif
 
 	if (forced || CDCInterfaceInfo->State.ControlLineStates.DeviceToHost != lines) {
 		CDCInterfaceInfo->State.ControlLineStates.DeviceToHost = lines;
@@ -256,9 +258,12 @@ void EVENT_CDC_Device_LineEncodingChanged(USB_ClassInfo_CDC_Device_t* const CDCI
 {
 	uint32_t baudrate = CDCInterfaceInfo->State.LineEncoding.BaudRateBPS;
 
+	if (baudrate == 9600)
+		baudrate = CAS_BAUDRATE_ABC80;
+
 	baudrate = fmtx_real_baudrate(baudrate);
 
-	if (baudrate != current_baudrate) {
+	if (1 || baudrate != current_baudrate) {
 		current_baudrate = baudrate;
 		fmtx_drain();
 		fmrx_set_speed(current_baudrate);