Who was Floyd Fitz? Enigma of the Caddo River
This short film is a back log of video footage that I’ve been releasing the older footage on The 8088 Record Collective YouTube channel.
Looking in the used cassette tape bins at small-town thrift stores can expose a hidden world of lost voices and ghostly apparitions. This documentary explores the tragic life of an enigmatic country music artist lost to obscurity. All the remains of Floyd Fitz are a handful of recordings and the legends passed down by the local residents.
If you have any information about Floyd Fitz, please contact us at whoisfloydfitz@gmail.com.
“Ĉu Iu Estas Tie?” (Short film in Esperanto)
Bethany and I made a short film for the American Good Film Festival back in March. It’s an anecdote centering around a child’s toy endowed with artificial intelligence that wakes up alone in a forgotten forest.
Bethany kaj mi faris mallongan filmeton por la Usona Bona Esperanto Film-festivalo antaŭ en marto. Ĝi estas rakonto ĉirkaŭ infana ludilo kun artefarita inteligenteco, kiu vekiĝas sole en forgesita arbaro.
Linux Audio Production: Getting started with Jack and MIDI
Last year, I posted this quick tutorial on the SMBA YouTube channel walking through the steps to use a MIDI controller with Jack using Xubuntu 20.04. I am posting it hear just for the sake of consistency and good housekeeping. Hopefully, I’ll get to make some more of these soon.
Running Autodesk EAGLE 9.6.2 on Xubuntu 22.04
So, I did a fresh install of Xubuntu 22.04 on a Dell Latitude 7390 with an Intel UHD 620 display adapter. I had some issues with the machine locking up just a few minutes after startup. I was able to resolve this by adding the following kernel option to the /etc/default/grub file.
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_psr=0"
The resolved that issue well enough, and most everything using OpenGL (e.g. Atom, Firefox, etc.) ran just fine after that. The only thing that was giving me trouble now was EAGLE. WebEngineContext would issue an error about not being able to initialize and then the program would seg fault.
WebEngineContext used before QtWebEngine::initialize() or OpenGL context creation failed. Failed to create OpenGL context for format QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1, stencilBufferSize 8, samples 0, swapBehavior QSurfaceFormat::SwapBehavior(DefaultSwapBehavior), swapInterval 1, profile QSurfaceFormat::OpenGLContextProfile(NoProfile)) [5376:5376:0100/000000.883007:ERROR:broker_posix.cc(41)] Invalid node channel message Aborted (core dumped)
After much googling, I came across a seemingly unrelated thread where they were removing some of the files from the internal lib folder to force EAGLE to use the system defaults. Since these seemed to be relevant to the error message I was getting, I decided to move the following library files into a folder named “backup” to see what would happen. Those files are shown here.
libX11-xcb.so.1 libxcb-dri2.so.0 libxcb-dri3.so.0 libxcb-glx.so.0 libxcb-present.so.0 libxcb-sync.so.1 libxcb-xfixes.so.0
After that, EAGLE actually opened. Of course, the fonts were huge on a very small 13.3″ screen. I had to go into Options -> User Interface to disable the “High DPI Scaling” option in order to get a more reasonable display.
Now, EAGLE seems to run beautifully. Fingers crossed that we can keep running Autodesk products on Linux in the future!
Arduino: Audio Frequency Generator
Back in good ol’ 2012 (the year the world was supposed to end), I posted some code for a simple Arduino controlled low-frequency oscillator (LFO). It has made its way into some very interesting projects over the years, but recently I was asked in the comments if the code could be modified to have a wider frequency output up into the kHz range. I thought it was a good question, so I made the effort to see what the limitations could be.
How It Works
So, the original LFO employs timers on an ATMega328 (or ATTiny85 depending on which version of the code) to generate the audio output. By using a wave table of a basic sine wave stored in an array, one timer (TIMER0) winds up setting the sample rate by grabbing each sample from the array at a configured interval, and the other timer (TIMER2) creates a PWM output on the selected pin (pin 3 in the code). So by setting an 8-bit value on OCR0A, the sample rate can be adjusted which adjusts the frequency on the output of TIMER2. The datasheet for the ATMega328 gives the following formula for the frequency of the output compare register.
If we take this formula and divide it by the number of samples, we get the output frequency. That means that the output frequency can also be scaled by reducing the number of samples available. So, I made a big output table in LibreOffice and saw that an OCR0A value of 128 was twice the frequency from 255. At 255, I could reduce the number of output samples by half and sweep over the same sample rates but get an increase in output frequency. This introduced a method of frequency scaling. The trade-off, however, is that the sine wave on the output is much less sinusoidal being that it has lower resolution, and that introduces higher order harmonics thus changing the timbre of the sine wave.
Another thing to keep in mind is that the sample rate from the output PWM gets very low and even into the audio range itself. This means that some kind of audio filter is needed on the output. I put a first order low-pass filter using a 2.2k series resistor and a 10 uF capacitor to ground. This worked surprisingly well, though some of the sampling noise shows up on the output at very low frequencies. Being an 8-bit audio signal, this isn’t much to worry about in the grand scheme of things since. I also found that the noise on the output could be lowered by implementing a simple moving average filter in the code on the 10-bit ADC input of the rate control if using a potentiometer to set the frequency. With the timer prescalar set to 64, we should get 64 clock ticks before the next sample is grabbed, so this left some room for some calculations to happen in between sample changes.
It’s all pretty experimental, but it seems to work alright. The frequency range is from around 1 Hz up to 14 kHz (more or less). If you’re using a pot to control the rate, use a linear one as the frequency output gets very logarithmic towards the top of the range.
The Code
// Project: Arduino Audio Frequency Signal Generator
// Version: 1.0
// Author: Abram Morphew
// Date: 2021.10.12
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
uint8_t sineTable256[] = {
128,131,134,137,140,143,146,149,152,155,158,162,165,167,170,173,
176,179,182,185,188,190,193,196,198,201,203,206,208,211,213,215,
218,220,222,224,226,228,230,232,234,235,237,238,240,241,243,244,
245,246,248,249,250,250,251,252,253,253,254,254,254,255,255,255,
255,255,255,255,254,254,254,253,253,252,251,250,250,249,248,246,
245,244,243,241,240,238,237,235,234,232,230,228,226,224,222,220,
218,215,213,211,208,206,203,201,198,196,193,190,188,185,182,179,
176,173,170,167,165,162,158,155,152,149,146,143,140,137,134,131,
128,124,121,118,115,112,109,106,103,100,97,93,90,88,85,82,
79,76,73,70,67,65,62,59,57,54,52,49,47,44,42,40,
37,35,33,31,29,27,25,23,21,20,18,17,15,14,12,11,
10,9,7,6,5,5,4,3,2,2,1,1,1,0,0,0,
0,0,0,0,1,1,1,2,2,3,4,5,5,6,7,9,
10,11,12,14,15,17,18,20,21,23,25,27,29,31,33,35,
37,40,42,44,47,49,52,54,57,59,62,65,67,70,73,76,
79,82,85,88,90,93,97,100,103,106,109,112,115,118,121,124
};
uint8_t sineTable128[] = {
128,134,140,146,152,158,165,170,176,182,188,193,198,203,208,213,
218,222,226,230,234,237,240,243,245,248,250,251,253,254,254,255,
255,255,254,254,253,251,250,248,245,243,240,237,234,230,226,222,
218,213,208,203,198,193,188,182,176,170,165,158,152,146,140,134,
128,121,115,109,103,97,90,85,79,73,67,62,57,52,47,42,
37,33,29,25,21,18,15,12,10,7,5,4,2,1,1,0,
0,0,1,1,2,4,5,7,10,12,15,18,21,25,29,33,
37,42,47,52,57,62,67,73,79,85,90,97,103,109,115,121 };
uint8_t sineTable64[] = {
128,140,152,165,176,188,198,208,218,226,234,240,245,250,253,254,
255,254,253,250,245,240,234,226,218,208,198,188,176,165,152,140,
128,115,103,90,79,67,57,47,37,29,21,15,10,5,2,1,
0,1,2,5,10,15,21,29,37,47,57,67,79,90,103,115
};
uint8_t sineTable32[] = {
128,152,176,198,218,234,245,253,255,253,245,234,218,198,176,152,
128,103,79,57,37,21,10,2,0,2,10,21,37,57,79,103,
};
uint8_t sineTable16[] = {
128,176,218,245,255,245,218,176,128,79,37,10,0,10,37,79
};
uint8_t sineTable8[] = {
128,218,255,218,128,37,0,37,128
};
uint8_t sineTable4[] = {
128,255,128,0,128
};
uint8_t sineTable2[] = {
255,0
};
uint8_t tWave = 128;
uint8_t sWave = 255;
uint8_t ruWave = 128;
uint8_t rdWave = 128;
uint8_t rWave = 128;
uint8_t inc = 1;
uint8_t r = 0;
int n = 32; // number of averages for ADC input (should be a power of 2: 32 max)
int ocr[32] = {};
int i = 0;
int t = 0; // time delay index for rate sweep
int sweep = 1023; // sweep
int rate = 0;
int waveform;
byte d = HIGH;
byte down = LOW; // increase freq if LOW, decrease freq if HIGH
byte rateSelectPin = 1;
byte waveSelectPin = 0;
void setup() {
pinMode(waveSelectPin, INPUT);
pinMode(rateSelectPin, INPUT);
pinMode(3, OUTPUT);
setupTimer();
OCR0A = 128;
}
void loop() {
// -- Waveform Selection
waveform = map(analogRead(waveSelectPin),0,1023,1,7);
//waveform = 1;
// -- Frequency Selection with ADC pin 1
if (r >= n) r = 0;
ocr[r] = map(analogRead(rateSelectPin),0,1023,1015,3);
r++;
// -- ADC input averaging
for(uint8_t c = 0; c < n; c++) { rate += ocr[c]; }
rate = floor(rate / n);
// Uncomment for frequency sweep
/*--------------------
if (t >= 2048) {
sweep--;
t = 0;
}
if (sweep <= 4) {
sweep = 1023;
}
t++;
rate = sweep;
//----------------------- */
// rate scaling with increasing frequency
if (rate < 128) {
inc = 128;
rate = rate * 2;
} else if ((128 <= rate) && (rate < 256)) {
inc = 64;
rate = rate;
} else if ((256 <= rate) && (rate < 384)) {
inc = 32;
rate = rate - 128;
} else if ((384 <= rate) && (rate < 512)) {
inc = 16;
rate = rate - 256;
} else if ((512 <= rate) && (rate < 640)) {
inc = 8;
rate = rate - 384;
} else if ((640 <= rate) && (rate < 768)) {
inc = 4;
rate = rate - 512;
} else if ((768 <= rate) && (rate < 896)) {
inc = 2;
rate = rate - 640;
} else if ((896 <= rate) && (rate < 1024)) {
inc = 1;
rate = rate - 768;
}
OCR0A = rate;
}
ISR(TIMER0_COMPA_vect) {
if(i >= (256 / inc)) i = 0;
switch(waveform) {
case 1:
OCR2B = sine(i, inc);
break;
case 2:
OCR2B = triangle(i);
break;
case 3:
OCR2B = square(i);
break;
case 4:
OCR2B = rampUp(i);
break;
case 5:
OCR2B = rampDown(i);
break;
case 6:
OCR2B = rand(i);
break;
case 7:
OCR2B = white(i);
break;
}
i++;
}
void setupTimer() {
cli();
/*--- TIMER2 CONFIG ---*/
sbi(TCCR2A,WGM20);
sbi(TCCR2A,WGM21);
cbi(TCCR2A,WGM22);
sbi(TCCR2A,COM2B1);
cbi(TCCR2A,COM2B0);
sbi(TCCR2B, CS20);
cbi(TCCR2B, CS21);
cbi(TCCR2B, CS22);
/*--- TIMER0 CONFIG ---*/
sbi(TCCR0B,CS00);
sbi(TCCR0B,CS01);
cbi(TCCR0B,CS02);
sbi(TCCR0A, COM0A1);
cbi(TCCR0A, COM0A0);
cbi(TCCR0A, WGM00);
sbi(TCCR0A, WGM01);
cbi(TCCR0A, WGM02);
cbi(TIFR0,OCF0A);
sbi(TIMSK0,OCIE0A);
sei();
}
int sine(int i, int inc) {
if (inc == 1) {
return sineTable256[i];
} else if (inc == 2) {
return sineTable128[i];
} else if (inc == 4) {
return sineTable64[i];
} else if (inc == 8) {
return sineTable32[i];
} else if (inc == 16) {
return sineTable16[i];
} else if (inc == 32) {
return sineTable8[i];
} else if (inc == 64) {
return sineTable4[i];
} else if (inc == 128) {
return sineTable2[i];
}
}
int triangle(int i) {
if(tWave >= 255) d = LOW;
if(tWave <= 0) d = HIGH;
if(d == HIGH) tWave = tWave + inc;
if(d == LOW) tWave = tWave + inc;
return tWave;
}
int rampUp(int i) {
ruWave = ruWave + inc;
if(ruWave > 255) ruWave = 0;
return ruWave;
}
int rampDown(int i) {
rdWave = rdWave + inc;
if(rdWave < 0) rdWave = 255;
return rdWave;
}
int square(int i) {
if(i >= (128 / inc)) sWave = 255;
if(i < (128/inc)) sWave = 0;
return sWave;
}
int rand(int i) {
if(i == (rWave / inc)) rWave = random(255);
return rWave;
}
int white(int i) {
return random(255);
}
Arduino: 1-Watt 2m Transmitter with RF Signal Generator
Since I do a lot of RF projects, I wanted to see if I could make a 2m power amplifier using a minimal set of components. I have a number of BS170 MOSFET transistors that I’ve used for dozens of applications over the years from guitar pedal pre-amps to digital control circuits. I started this project by building a class A amplifier on a bare piece of copper laminate. I was able to get 9 dB of gain with a power output of 15 dBm and a quiescent current of 83 mA. The schematic is shown below. R3 and R4 can be omitted if you happen to be building the circuit and replaced with 50 ohm SMA connectors. I used a variable cap at C3 to tune the circuit for maximum output power,
With 15 dBm of output power, I thought this would be adequate to drive a power amplifier stage. I nabbed some 2SC1970 transistors off eBay for a few bucks and started experimenting with the application circuit in the datasheet. This transistor is quite old by modern standards, but they were cheap and in a TO-220 package, so I figured they could take a beating. The standard application circuit was a good jumping off point for starting the design, and I was able to easily make changes to the air-core inductors by compressing and stretching the windings. I wound up just getting as close as I could with the inductors and relying on the variable capacitors in the circuit to get as much power as I could.
The LO portion of the transmitter was an Si5351 clock signal generator controlled by an ATMega2560 Arduino board. It’s able to get up to 160 MHz (200 MHz now in the Si5351B chips) and is programmed via an I2C port. I setup button 5 (Select) on the LCD shield to enable the LO later on, but I just had it running originally at startup and then connected the straight key in series with the 12V supply (widow-maker style) to the PA.
Above is the measured output on the old Tektronix TDS 360 oscilloscope. Measured power output is right at 1 watt. The second harmonic is a little higher than I would have liked, but an added LPF to the output should help fix that right up. The last thing to do was to get out in the rain in January and see if someone could pick it up. I hooked up a 3-element yagi to the output and the signal from the transmitter was picked up by W7YOZ in Shelton, WA some 22 miles to the north east.
Of course, here is the Arduino code for the RF signal generator using the Adafruit Si5351 clock generator board. The controls need to be incorporated into an interrupt trigger to make the thing more controllable, but it hasn’t been so annoying that I’ve needed to fix it as of yet. Just fair warning in case someone out there in the world decides to use it for anything.
// Arduino RF Signal Generator
// author: Abram Morphew
// date: 2019.04.25
#include <Wire.h>
#include <Adafruit_SI5351.h>
#include <LiquidCrystal.h>
Adafruit_SI5351 clockgen = Adafruit_SI5351();
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
long frequency = 144100000;
long inc = 1000;
char* data = "0";
int btn = 0;
bool keyPress = false;
bool enable = false;
void setup() {
lcd.begin(16,2);
lcd.print("Initialize");
delay(500);
/* Initialise the sensor */
if (clockgen.begin() != ERROR_NONE) {
lcd.print("Ooops, no Si5351 detected ... Check your wiring or I2C ADDR!");
while(1);
}
setfrequency(frequency);
delay(100);
lcd.clear();
}
void loop() {
if (keyPress == true) {
setfrequency(frequency);
keyPress = false;
}
// set title:
lcd.setCursor(0,0);
lcd.print("Frequency: ");
// update frequency
lcd.setCursor(0, 1);
lcd.print(frequency/1e6,3);
lcd.print(" MHz ");
btn = readkeypad();
if ((btn == 1) && (frequency + inc <= 155e6)) { frequency = frequency + inc; keyPress = true; delay(100); }
if ((btn == 2) && (frequency - inc >= 420e3)) { frequency = frequency - inc; keyPress = true; delay(100); }
if ((btn == 3) && (inc < 1e8)) { inc = inc * 10; delay(100); }
if ((btn == 4) && (inc > 1e4)) { inc = inc / 10; delay(100); }
if (btn == 5) {
clockgen.enableOutputs(true);
}
if (btn != 5) {
clockgen.enableOutputs(false);
}
delay(10);
}
int readkeypad(){
int adc_key_in = analogRead(0); //
int ret = 0;
if (adc_key_in < 50) ret = 4;
if ( (adc_key_in > 800) && (adc_key_in < 1150)) ret = 0;
if ( (adc_key_in > 80) && (adc_key_in < 150) ) ret = 1;
if ( (adc_key_in > 250) && (adc_key_in < 350) ) ret = 2;
if ( (adc_key_in > 400) && (adc_key_in < 500) ) ret = 3;
if ( (adc_key_in > 500) && (adc_key_in < 800) ) ret = 5;
//lcd.print(adc_key_in);
return ret;
}
int setfrequency(long frequency) {
int m = 0;
int n = 0;
int fs = 8;
clockgen.enableOutputs(false);
if (frequency > 55e6) {
fs = 8;
} else if ((frequency <= 55e6) && (frequency > 25e6)) {
fs = 16;
} else if ((frequency <= 25e6) && (frequency > 10e6)) {
fs = 32;
} else if ((frequency <= 10e6) && (frequency > 6e6)) {
fs = 64;
} else if ((frequency <= 6e6) && (frequency > 3e6)) {
fs = 128;
} else if ((frequency <= 6e6) && (frequency > 2.1e6)) {
fs = 256;
} else if ((frequency <= 2.1e6) && (frequency > 1e6)) {
fs = 512;
} else if (frequency <= 1e6) {
fs = 900;
}
// determine m, n, and d from frequency value
m = floor(frequency*fs/25e6);
n = ((frequency*fs/25e6) - m)*1000;
clockgen.setupPLL(SI5351_PLL_A, m, n, 1000);
clockgen.setupMultisynth(0, SI5351_PLL_A, fs, 0, 1);
}
Portable 40m Direct-conversion Transceiver Design
Having finished my master’s degree over a year ago now, I’ve started to see my thesis show up on various academic web sites. I decided I should probably link it on this site in the event that anyone is interested in building and/or designing their own QRP mono-band radio. Additionally, I’ve been doing some more experiments with QRP setups and like using this rig as a qualification vehicle. Being a mono-bander with a very narrow receive bandwidth, I just find it more sensitive to picking up weak signals, and it’s very easy to listen to when operating in less noisy environments. I’ve done a lot of comparisons with the KX3 (thanks to KK7B), and sometimes it’s just easier to copy signals closer to the noise floor on the DCT.
With that being said, any later posts that utilize this transceiver will point back here for reference. A full text PDF of the design is listed here:
73s DE K2NXF
200 kHz Arduino Clock Generator
Someone contacted me recently about using an ATMega328 to generate a 200 kHz clock signal for a BBD analog delay chip. I finally had a few minutes today to sit down and ensure that this code works. Varying the OCR0A value acts as a frequency adjustment on the output following the formula: f = 16e6 / (4 * OCR0A) where OCR0A != 0. With a value of 0, the output frequency is roughly 8 MHz. It seemed fairly stable enough at this frequency, but I imagine that it would start having issues with more instructions. Either way, it makes for a very usable clock signal in the kHz range. I’ll try it out on a BBD hopefully one day myself and see.
// ===== 200 kHz Clock Signal Generator ==== //
int pin = 6;
byte data = LOW;
void setup() {
setupTimer();
pinMode(pin, OUTPUT);
// f = 16e6 / (4 * OCR0A)
OCR0A = 20; // varies CLK frequency: 0 => 8 MHz, 255 => 16 kHz
digitalWrite(pin,data);
}
void loop() {
}
void setupTimer() {
cli();
/*--- TIMER0 CONFIG ---*/
TCCR0A = 0b11000001;
TCCR0B = 0b00001001; // last 3 bits set prescalar for Timer0
TIMSK0 = 0b00000010; // set OCIE0A high
TIFR0 = 0b00000010; // set OCF0A high
sei();
}
ISR(TIMER0_COMPA_vect) {
data = !data;
digitalWrite(pin, data);
}
</pre>
Amongst Projects: Therematron
Here’s an beautiful synth project I found by Steve Roberts at Amongst Projects that utilizes some work I did back in 2012 with my Arduino LFO. It’s always a pleasure to find my own work buried in someone else’s. I recommend heading over and checking out the post. You won’t be sorry.