add tagsu-avr-modem from Rakettitiede Oy

3 files changed, 230 insertions, 0 deletions

diff --git a/modem.c b/modem.c
new file mode 100644
index 0000000..db4c296
--- /dev/null
+++ b/modem.c
@@ -0,0 +1,95 @@
+/* Name: modem.c
+ *
+ * Audio modem for Attiny85 & other AVR chips with modifications
+ *
+ * Author: Jari Tulilahti
+ * Copyright: 2014 Rakettitiede Oy
+ * License: LGPLv3, see COPYING, and COPYING.LESSER -files for more info
+ */
+
+#include "modem.h"
+
+/* Ring buffer global variables */
+static volatile uint8_t modem_buffer_head = 0, modem_buffer_tail = 0;
+static volatile uint8_t modem_buffer[MODEM_BUFFER_SIZE];
+
+/*
+ * Returns number of available bytes in ringbuffer or 0 if empty
+ */
+uint8_t modem_buffer_available() {
+	return modem_buffer_head - modem_buffer_tail;
+}
+
+/*
+ * Store 1 byte in ringbuffer
+ */
+static inline void modem_buffer_put(const uint8_t c) {
+	if (modem_buffer_available() != MODEM_BUFFER_SIZE) { 
+		modem_buffer[modem_buffer_head++ % MODEM_BUFFER_SIZE] = c;
+	} 
+}
+
+/*
+ * Fetch 1 byte from ringbuffer
+ */
+uint8_t modem_buffer_get() {
+	uint8_t b = 0;
+	if (modem_buffer_available() != 0) {
+		b = modem_buffer[modem_buffer_tail++ % MODEM_BUFFER_SIZE];
+	}
+	return b;
+}
+
+/*
+ * Pin Change Interrupt Vector. This is The Modem.
+ */
+ISR(PCINT0_vect) {
+	/* Static variables instead of globals to keep scope inside ISR */
+	static uint8_t modem_bit = 0;
+	static uint8_t modem_bitlen = 0;
+	static uint8_t modem_byte = 0;
+
+	/* Read & Zero Timer/Counter 1 value */
+	uint8_t modem_pulselen = MODEM_TIMER;
+	MODEM_TIMER = 0;
+
+	/*
+	 * Check if we received Start/Sync -pulse.
+	 * Calculate bit signal length middle point from pulse.
+	 * Return from ISR immediately.
+	 */
+	if (modem_pulselen > MODEM_SYNC_LEN) {
+		modem_bitlen = (modem_pulselen >> 2);
+		modem_bit = 0;
+		return;
+	}
+
+	/*
+	 * Shift byte and set high bit according to the pulse length.
+	 * Long pulse = 1, Short pulse = 0
+	 */
+	modem_byte = (modem_byte >> 1) | (modem_pulselen < modem_bitlen ? 0x00 : 0x80);
+
+	/* Check if we received complete byte and store it in ring buffer */
+	if (!(++modem_bit % 0x08)) {
+		modem_buffer_put(modem_byte);
+	}
+}
+
+/*
+ * Start the modem by enabling Pin Change Interrupts & Timer
+ */
+void modem_init()  {
+	/* Modem pin as input */
+	MODEM_DDR &= ~(1 << MODEM_PIN);
+
+	/* Enable Pin Change Interrupts and PCINT for MODEM_PIN */
+	GIMSK |= (1 << PCIE);
+	PCMSK |= (1 << MODEM_PIN);
+
+	/* Timer: TCCR1: CS10, CS11 and CS12 bits: 8MHz clock with Prescaler 64 = 125kHz timer clock */
+	TCCR1 = (1 << CS10) | (1 << CS11) | (1 << CS12);
+
+	/* Enable interrupts */
+	sei();
+} 
diff --git a/modem.h b/modem.h
new file mode 100644
index 0000000..7fa5211
--- /dev/null
+++ b/modem.h
@@ -0,0 +1,24 @@
+/* Name: modem.h
+ * Author: Jari Tulilahti
+ * Copyright: 2014 Rakettitiede Oy
+ * License: LGPLv3, see COPYING, and COPYING.LESSER -files for more info
+ */
+
+#pragma once
+
+#include <avr/interrupt.h>
+#include <stdlib.h>
+
+/* Modem ring buffer size must be power of 2 */
+#define MODEM_BUFFER_SIZE	4
+
+/* Modem defines */
+#define MODEM_SYNC_LEN		42
+#define MODEM_TIMER		TCNT1
+#define MODEM_PIN 		PCINT3
+#define MODEM_DDR		DDRB
+
+/* Public funtions */
+uint8_t modem_buffer_available();
+uint8_t modem_buffer_get();
+void modem_init();
diff --git a/utilities/modem.py b/utilities/modem.py
new file mode 100644
index 0000000..f2e2b1b
--- /dev/null
+++ b/utilities/modem.py
@@ -0,0 +1,111 @@
+#!/usr/bin/env python
+
+import sys, wave
+
+#
+# "Modem" wav creator for "Next Gen" Tagsu Modem :)
+#
+# Author: Jari Tulilahti
+# Copyright: 2014 Rakettitiede Oy
+# License: LGPLv3, see COPYING and COPYING.LESSER -files for more info
+#
+# Usage:
+#	python modem.py <input_filename> [output_wav_filename] [samplerate]
+#
+# Default sample rate is 48000
+# Default output to stdout if no wav filename given
+#
+# Working sample rates are between 16000 - 48000:
+#
+# 16000 (~4000 bps)
+# 22050 (~5500 bps)
+# 24000 (~6000 bps)
+# 32000 (~8000 bps)
+# 44100 (~11025 bps)
+# 48000 (~12000 bps)
+#
+# NOTICE:
+#
+# Actual speed depends of the data, as zeroes and ones take
+# different amount of samples, the more zeros, the faster the speed.
+# Average bps has been calculated using data "0101010101..."
+#
+
+class modem:
+
+	bits = [[3 * chr(0), 5 * chr(0)], [3 * chr(255), 5 * chr(255)]]
+	sync = [17 * chr(0), 17 * chr(255)]
+	hilo = 0
+
+	# Nothing here
+	def __init__(self):
+		pass
+
+	# Generate one sync-pulse
+	def syncsignal(self):
+		self.hilo ^= 1
+		return self.sync[self.hilo]
+
+	# Decode bits to modem signals
+	def modemcode(self, byte):
+		bleep = ""
+		for x in xrange(8):
+			self.hilo ^= 1
+			bleep += self.bits[self.hilo][byte & 0x01]
+			byte >>= 1
+		return bleep
+
+	# Return <length> samples of silence
+	def silence(self, length):
+		return chr(127) * length
+
+
+if len(sys.argv) < 2:
+	print """Usage: {0} <input_filename> [output_wav_filename] [samplerate]
+
+	input_filename		Data file as input to modem.
+	output_wav_filename	Write output-wav to this file. If empty, output to STDOUT.
+	samplerate		Sample rate between 16000 - 48000. Default is 48000.
+	""".format(sys.argv[0])
+	sys.exit()
+
+sound = ""
+
+m = modem()
+cnt = 0
+
+# Add silence
+# sound += m.silence(24000)
+
+# Add 4 sync signals to start
+for x in xrange(4):
+	sound += m.syncsignal()
+
+# Send Actual data
+f = open(sys.argv[1])
+for byte in f.read():
+	sound += m.modemcode(ord(byte))
+
+	# Add counter
+	cnt += 1
+
+	# After every 10 bytes, send 2 sync signals
+	if cnt == 10:
+		for x in xrange(2):
+			sound += m.syncsignal()
+		cnt = 0
+
+# End transmission with few sync-signals
+for x in xrange(4):
+	sound += m.syncsignal()
+
+# Output the generated sound (no wav headers)
+if len(sys.argv) <= 2:
+	print sound
+else:
+	freq = int(sys.argv[3]) if len(sys.argv) > 3 else 48000
+	wav = wave.open(sys.argv[2], 'wb')
+	wav.setparams((1, 1, freq, 0, "NONE", None))
+	wav.writeframes(sound)
+	wav.close()
+