1 files changed, 82 insertions, 0 deletions
diff --git a/src/modem.h b/src/modem.h
new file mode 100644
index 0000000..7409214
--- /dev/null
+++ b/src/modem.h
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+/* Name: modem.h
+ * Author: Jari Tulilahti
+ * Copyright: 2014 Rakettitiede Oy and 2016 Daniel Friesel
+ * License: LGPLv3, see COPYING, and COPYING.LESSER -files for more info
+ */
+
+#ifndef MODEM_H_
+#define MODEM_H_
+
+#include <avr/interrupt.h>
+#include <stdlib.h>
+
+/* Modem ring buffer size must be power of 2 */
+#define MODEM_BUFFER_SIZE	64
+
+/* Modem defines */
+#define MODEM_SYNC_LEN		42
+#define MODEM_TIMER		TCNT1L
+#define MODEM_PCINT		PCINT24
+#define MODEM_PCMSK		PCMSK3
+#define MODEM_PCIE		PCIE3
+#define MODEM_PIN		PA0
+#define MODEM_DDR		DDRA
+
+/**
+ * Receive-only modem. Sets up a pin change interrupt on the modem pin
+ * and receives bytes using a simple protocol. Does not detect or correct
+ * transmission errors.
+ */
+class Modem {
+	private:
+		uint8_t buffer_head;
+		uint8_t buffer_tail;
+		uint8_t buffer[MODEM_BUFFER_SIZE];
+		bool new_transmission;
+		void buffer_put(const uint8_t c);
+	public:
+		Modem() {new_transmission = false;};
+
+		/**
+		 * Checks if a new transmission was started since the last call
+		 * to this function. Returns true if that is the case and false
+		 * otherwise.
+		 * @return true if a new transmission was started
+		 */
+		bool newTransmission();
+
+		/**
+		 * Checks if there are unprocessed bytes in the modem receive buffer.
+		 * @return number of unprocessed bytes
+		 */
+		uint8_t buffer_available(void);
+
+		/**
+		 * Get next byte from modem receive buffer.
+		 * @return next unprocessed byte (0 if the buffer is empty)
+		 */
+		uint8_t buffer_get(void);
+
+		/**
+		 * Enable the modem. Turns on the input voltage divider on MODEM_PIN
+		 * and enables the receive interrupt (MODEM_PCINT).
+		 */
+		void enable(void);
+
+		/**
+		 * Disable the modem. Disables the receive interrupt and turns off
+		 * the input voltage divider on MODEM_PIN.
+		 */
+		void disable(void);
+
+		/**
+		 * Called by the pin change interrupt service routine whenever the
+		 * modem pin is toggled. Detects sync pulses, receives bits and
+		 * stores complete bytes in the buffer.
+		 *
+		 * Do not call this function yourself.
+		 */
+		void receive(void);
+};
+
+#endif /* MODEM_H_ */