Previously, I’ve picked up several transistors as candidates to be used for noise source for noise generator.

https://gaje.jp/2014/01/14/2915/

I’ve started testing these transistors.

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This works for windows.

http://stackoverflow.com/questions/12175964/python-method-for-reading-keypress

However, you cannot use this feature from cygwin.  You need to invoke python script directly from Windows.  Double-clicking the python script works, but you need to catch exceptions in the case (otherwise, you don’t know what happened when an exception was raised).

Here is the sample program to read arrow keys.

#!c:\Python32\python

from msvcrt import getch
import sys

print("press ESC to exit")

while True:
    try:
        key = ord(getch())
        if key == 27: #ESC
            break
        elif key == 224: # special keys (arros, f keys, ins, del, etc.)
            key = ord(getch())
            if key == 75:
                print("left")
            elif key == 77:
                print("right")
            elif key == 80:
                print("down")
            elif key == 72:
                print("up")
    except:
        print(sys.exc_info()[0])

This link helped

http://stackoverflow.com/questions/307305/play-a-sound-with-python

I’m working on Windows, so winsound worked.  It was as simple as

#!/usr/bin/env python

import winsound

winsound.PlaySound("ex1.wav", winsound.SND_FILENAME)

As mentioned in my previous post, AVI Dragon’s SPI pins in debugWire interface have to be disconnected during debug run in order to properly run an application that uses SPI / USI.  I also noticed that the Dragon dominates RESET pin, too.  In my project, I’m resetting target chip from Arduino.  The Dragon is killing this functionality as well.  This makes me quite uncomfortable with my development work, so I’ve enhanced the switch I made on bread board previously, and made a helper device.  It’s nicely working.  I named it “Dragon’s Tail”.

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AVR Dragon provides on-chip debugging feature through debugWire interface.  The debugWire utilizes the ISP six-pin header to control the target device as shown in the following link:

http://www.atmel.no/webdoc/avrdragon/avrdragon.section.zrr_osd_lc.html

However, the target application does not work correctly with SPI feature during debug run.

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Typical analog noise generators make signal by amplifying AC component coming out from zener current of transistors reversely biased between emitter and base (here’s an example circuit).

Any bipolar transistor would work as such a noise source, but noise quality in listening is different from part numbers.  2SC828A is well known as good noise source, but it’s been obsolete for long.  So for Analog2.0, I have been recommending 2SC3311 instead.  But this part becomes obsolete as well.  Now I have to find another one.

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As a part of my current experiment, I’m running following piece of code:

   if (digitalRead(pinDeviceReadReady) == HIGH) {
    Serial.println("DATA READY");
    spiSend(0x20); // command "read request"
    readBuffer.deviceId = spiReceive();
    Serial.println(readBuffer.deviceId);
    readBuffer.wireId = spiReceive();
    Serial.println(readBuffer.wireId);
    readBuffer.length = spiReceive();
    Serial.println(readBuffer.length);
    for (int i = 0; i <= readBuffer.length; ++i) {
       readBuffer.data[i] = spiReceive();
       Serial.println(readBuffer.data[i]);
    }
  }

where

inline void spiSend(uint8_t data)
{
  // wait for device ready to write
  while (digitalRead(pinDeviceWriteReady) == LOW);
  SPI.transfer(data);
}

inline uint8_t spiReceive()
{
  while (digitalRead(pinDeviceReadReady) == LOW);
  uint8_t data = SPI.transfer(0);
  return data;
}

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I’m going to try making a digital communication bus for synthesizer modules.

Analog synth has a very simple control language which is voltage.  Any message is translated to voltage that can be read by any modules that accept voltage input. So for example, VCO output is basically audio output but also can be used as control voltage of some other modules, such as VCO cross modulation.

This simple data exchange methodology makes analog synthesizer very versatile and flexible.  However, as a drawback, patch wiring would become too complicated as you make complex module network.

One solution for making the wiring simple is to use a single common data bass where all modules are connected, and exchange data selectively using some software.  Apparently, making such a bass for analog signals is impossible or extremely difficult. So I’m going to try making it using a digital bass.

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