Category Archives: Computer

Screens and DIY projects

Below some examples and connection diagrams to control displays.
More code and complete schematics will be added on this page or on a separate projects page.

UPDATE 20230119 Cost of 20×4 display in 1998

LCD

I’ve used a LCD display like this (HITACHI HD44780) on my PC in the 90s, and also written code to use this as a monitoring device on my amiga.

On Linux i used LcdProc – This module also was equiped with a serial connector
Now (2023) it is 8 euros!
When bought now fl to euro 98 Euro or 107 $
;LCD Display Module             Parallel port
;        1 Vss                  20 GND
;        2 Vdd                  14 +5V
;        3 Vlc                  20 GND (contrast LCD display)
;        4 RS (register select) 11 BUSY
;        5 R/W                  12 POUT
;        6 E (enable)           13 SEL
;        7 DB0                   2 D0
;        8 DB1                   3 D1
;        9 DB2                   4 D2
;       10 DB3                   5 D3
;       11 DB4                   6 D4
;       12 DB5                   7 D5
;       13 DB6                   8 D6
;       14 DB7                   9 D7
Amiga code part
        bsr     initprt         ; CIA 8520 init
        bsr     initlcd         ; init lcd display module
        move.l  #0,d0
        rts

initprt:move.b  #$ff,$bfe301    ; parallel port is output
        move.b  $bfd200,d0
        ori.b   #$07,d0         ; select, p-out and busy
        move.b  d0,$bfd200      
        rts

initlcd:move.w  #$38,d0         ; multiple reset
        bsr     send
        bsr     delay2
        move.w  #$38,d0
        bsr     send
        bsr     delay2
        move.w  #$38,d0         ; 2*8 lines
        bsr     send
        bsr     delay2
        move.w  #$01,d0         ; clear display
        bsr     send
        bsr     delay2          ; wait
        move.w  #$0c,d0         ; display on
        bsr     send
        move.w  #$06,d0         ; Entry Mode Set
        bsr     send
        rts

send:   bsr     delay
        btst    #8,d0           ; test rs bit
        beq     reg0
        bsr     rs1             ; select register 1
        bra     skip
reg0:   bsr     rs0             ; select register 0
skip:
        bsr     delay
        bsr     rw0             ; read/write=0 
        bsr     delay
        bsr     e1              ; enable = 1
        bsr     delay
        move.b  d0,$bfe101      ; push data
        bsr     delay
        bsr     e0              
        bsr     delay
        rts

delay:  move.w  #$20,d1
dloop:  subi    #1,d1
        bne     dloop
        rts

delay2: move.w  #$800,d1
dloop2: subi    #1,d1
        bne     dloop2
        rts
Part of my MQTT display alarm thingy
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>  
LiquidCrystal_I2C lcd(0x27, 20, 4);
const char* ssid = "MYACCESSPOINT";
const char* password = "MYPASSWORD";
const char* mqtt_server = "mymqttserver";
const byte ledRed = 12;
const byte horn = 13;
int button = 2;
int press = 0;
boolean buttonToggle = true;


// Todo : DISPLAY 2ND LINE, DISPLAY SILENT, ...

WiFiClient espClient;
PubSubClient client(espClient);
bool toggle = false;
void setup_wifi() {
  delay(100);

  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  randomSeed(micros());
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* payload, unsigned int length)
{
  if (length > 0) {
    toggle = true;
  }

  if (length == 0) {
    toggle = false;
  }

  Serial.print("Command from MQTT broker is : [");
  Serial.print(topic);

  Serial.println();
  Serial.print(" publish data is:");
  lcd.clear();
  lcd.backlight(); // turn off backlight

  {
  
    for (int i = 0; i < length; i++)
    {
      Serial.print((char)payload[i]);
      if (i < 16){
      lcd.setCursor(0, 0);
      lcd.setCursor(i, 0);
      } else {
      lcd.setCursor(0, 1);
      lcd.setCursor(i-16, 1);
      }
      lcd.write((char)payload[i]);
    }
  }


  Serial.println();
} 

void reconnect() {
  
  while (!client.connected())
  {
    Serial.print("Attempting MQTT connection...");
    
    String clientId = "mqttlcd";
    clientId += String(random(0xffff), HEX);

    if (client.connect(clientId.c_str()))
    {
      Serial.println("connected");

      client.subscribe("mqttlcd/message");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(6000);
    }
  }
} 

void setup() {
  Serial.begin(115200);
  pinMode(button, INPUT);
  digitalWrite(2, HIGH);
  pinMode(ledRed, OUTPUT);
  digitalWrite(ledRed, LOW);
  pinMode(horn, OUTPUT);
  digitalWrite(horn, LOW);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  lcd.init(); 
  lcd.backlight();
}

void loop() {

  
  if (!client.connected()) {
    reconnect();
  }
  if (toggle == true) {
    digitalWrite(ledRed, HIGH);
    digitalWrite(horn, HIGH);
    delay(200);
    digitalWrite(ledRed, LOW);
    digitalWrite(horn, LOW);
    delay(200);
  }
  if (toggle == false) {
    digitalWrite(ledRed, LOW);
    digitalWrite(horn, LOW);

  }

  client.setCallback(callback);
  client.loop();

  press = digitalRead(button);
  if (press == LOW)
  {
    if (buttonToggle)
    {
      digitalWrite(ledRed, HIGH);
      digitalWrite(horn, HIGH);
      buttonToggle = !buttonToggle;
    }
    else
    {
      digitalWrite(ledRed, LOW); 
      digitalWrite(horn, LOW);
      buttonToggle = !buttonToggle;
      toggle = false;
      client.publish("mqttlcd/button","pressed");
      lcd.clear();
      lcd.noBacklight(); // turn off backlight
    }
  }
  delay(500);  //delay for debounce
}

Oled

There are several oled displays, mostly controllable with i2c but some of them are SPI

SSD1306 – I2c connected

Using a wemos – Octoprint project for example
Octoprint (Note: this is NOT a multicolor display 1/4 of the display is yellow. )
My notification watch. Runs on a ESP12F connects to Wifi, has a piezo sound element
Using a raspberry (Part of my Lab Sensors Project)
pip3 install adafruit-circuitpython-ssd1306
git clone https://github.com/adafruit/Adafruit_Python_SSD1306 (old)
Edit file - comment SPI section

Some arduino’s have embedded displays like those i’ve used for a Lora project.

Other means of connecting : SPI

SPI connected display

Nextion

Nextion is a Human Machine Interface (HMI) solution combining an onboard processor and memory touch display with Nextion Editor software for HMI GUI project development.

Using the Nextion Editor software, you can quickly develop the HMI GUI by drag-and-drop components (graphics, text, button, slider, etc.) and ASCII text-based instructions for coding how components interact on the display side.

Nextion HMI display connects to peripheral MCU via TTL Serial (5V, TX, RX, GND) to provide event notifications that peripheral MCU can act on, the peripheral MCU can easily update progress, and status back to Nextion display utilizing simple ASCII text-based instructions.

My nextion domoticz box, tilt to wakeup
Domoticz controller

My biltong box using a Nextion

Raspberry displays

 3.5inch RPi Display – 480×320 Pixel – XPT2046 Touch Controller
edit cmdline.txt
add "fbcon=map:10 fbcon=font:ProFont6x11 logo.nologo"
at the end
edit config.txt
add between custom comments at the bottom
dtoverlay=piscreen,speed=24000000,rotate=90
# Or check http://www.lcdwiki.com/3.5inch_RPi_Display

Above display’s i’ve used for Picore Players and the Lidar POC

To try: Getting above display running with a arduino
https://github.com/PaulStoffregen/XPT2046_Touchscreen

Raspberry HDMI display

Easiest of them all, just connect with HDMI, there is a adaptor for hdmi-hdmi (versions 1,2,3) and hdmi-mini-hdmi for RPi4 variants.

Epaper and 7-Segment displays

Other means of displaying information are for example

Epaper

ESP with epaper module, disconnected power for a while, artifacts appear.

7 Segment displays

I used a lot of 7-Segment display’s in the past. They look cool and are hardcore.

My homebrew computer uses this

Nixie tubes!

And there are https://en.wikipedia.org/wiki/Nixie_tube .. I’ve never had those

Above bigger 2D display i used with Wled and a digital microphone, so its sound reactive. The lower part i got in recently .

inmp441 digital microphone

Using OSB to record screens

While you can use screencapture to record virtual machines, to real machines it is a different story.

Virtual machines running locally or remote can be accessed with spice/vnc or rdesktop.
So you have a window displaying the remote screen, which you can capture using window capture.

There are also emulators which you can window-capture. But i want the real thing when available. Emulators give a too crisp screen output. And you want to have the real SID chip sound.

Hardware capturing:

I’ve got two capturing usb sticks:

Camlink 4K for hdmi capturing (Which i use mainly for my nikon)

Basetech BR116 RCA and S-Video capture (NTSC 720 x 480 , 30 FPS/PAL 720 x 576 , 25 FPS)

Devices and recording:

  • C64 – Use Basetech, and the DIN to RCA cable
  • Vic-20 – same as above
  • Raspberry – Use a HDMI and Camlink
  • Amiga – I use the basetech and grab the composite signal from the Scart connector, another solution is to use a A520 Modulator, which has Composite out. (There are schematics on the internet to connect hdmi to your amiga)
Amiga A520 Modulator

The 520 Modulator connects to the amiga using a DB23 connector, and a Y cable for the 2 rca audio jacks.
It outputs a composite video signal, and RF modulated signal to connect to a old Tube/Crt monitor

When recording video from those screens, i configure my OBS file format to MP4. This makes it easier to embed into websites. Only downside on writing to MP4 instead of mkv is the fact that the file probably isn’t recoverable when something crashes.

Audio capturing :

When capturing your movie don’t forget to add a audio source to your OBS sources.
Use Audio input capture, or you can use Audio output capture when sound is playing by your system.

Demo a friend made using a demomaker (Music starts half way)

Flightsim on a Amiga (See more on flightsims)
C64 Hellraiser (part 1) no de-comb/de-interlace filter

Note: check your output/cables
https://www.youtube.com/watch?v=entQosOLjEI

Morse with a ATTINY85

Using above schematic and attiny program you can make a mini morse trainer. It runs on a single CR2032!

I’ve got a attiny85 programmer as pictured below.

A Attiny85 chip is a 8 pin microcontroller, but with far less pin’s and its most of the times just a DIP/DIL (Dual in line)

When using the Arduino IDE:

  • Preferences : Add board url :
    https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json
  • Set board info like: (NOTE PROGRAMMER USBasp)
  • Burn bootloader
  • After that compile and upload

Source code used: https://github.com/andyhighnumber/Attiny-Arduino-Games/tree/master/MorseAttinyArcade

I had to short JP2 to get the USBasp into slow burn mode, else the attiny85 could not be found

Hard to do without a propper morse key!

HuskyLens Test

I’ve bought a Husky lens recently. It was very cheap for what you get.
(50 Euro’s)
The first tests are promising.

Nice little, but powerful gadget.
https://wiki.dfrobot.com/HUSKYLENS_V1.0_SKU_SEN0305_SEN0336

Cables to connect Rpi or Arduino, mounts, Huskylens and Protectioncover (sold separately)
  • face recognition
  • object tracking
  • object recognition
  • line tracking
  • color recognition
  • tag recognition
  • object classification

Communication can be done via I2C and Uart.
Uses a sdcard to store learning data.
Has white leds for object lighting.

Build-in objects which are recognised out of the box. (Others can be learned by the device)

aeroplane, bicycle, bird, boat, bottle, bus, car, cat, chair, cow, dining-table, dog, horse, motorbike, person, potted plant, sheep, sofa, train, TV

Photo manager addition using ML!

A few years ago i wrote a photo manager .. again .. ( see post about my first previous photo manager )
It is a web gui to find photos in my huge photo archive.
I manually added 190k tags to 120k photos in 20+ years.

I thought wouldn’t it be nice if i can generate additional metadata using Machine Learning. A few years ago i did some testing and followed a podcast and free course about machine learning.

So today i started to implement a addition to my gui. Machine recognition tags!

It already kinda works.

Things to do :

  • Make it a background job, my fileserver doesn’t run Tensorflow on a GPU, so it is slooow
  • Embed in existing GUI and stats
  • Design a editor to remove wrong tags

Below a part of ML images

Command to get a thumbnail sheet with only directory names:

montage -verbose -units PixelsPerInch -density 300 -tile 7x6 -label "%d" -font Arial -pointsize 6 -background "#FFFFFF" -fill "black" -define jpeg:size=253x154 -geometry 253x154+2+2 -auto-orient */*.JPG -title "ML Thumbs" thumbsheet.jpg

Maybe, i can use debug output like below.

['lakeside, lakeshore (score = 0.47934)', 'seashore, coast, seacoast, sea-coast (score = 0.11385)', 'sandbar, sand bar (score = 0.08822)', 'breakwater, groin, groyne, mole, bulwark, seawall, jetty (score = 0.06281)', 'valley, vale (score = 0.01790)', '']

Scraping podcast which uses a javascript to obfuscate mp3 links

wget-ting the page only gave me flat html, but no readable links.

We need the rendered version, phantomjs wil help

wget https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2

printsource.js

var system = require('system');
var page   = require('webpage').create();
var url    = system.args[1];
page.open(url, function () {
  console.log(page.content);
  phantom.exit();
});

Run phantomjs

phantomjs-2.1.1-linux-x86_64/bin/phantomjs printsource.js  https://xxxxxxxx/show/xxxx > out

So now i got the rendered page, get mp3’s and titles, for this example

cat out | sed 'N;s/\n/,/' | cut -f2,7 -d\" | while read line ; do
mp3=$( echo $line | cut -f1 -d\")
title=$( echo $line | cut -f3 -d\&gt; | tr -d '/&lt;&gt;[]]\!,;' | tr -d "'" | sed s/CDATA//g | sed s#title##g | sed s/:/-/g )
echo "$mp3 $title"
wget $mp3 -O "$title.mp3"
done

bash downloadscript
done

Portable Logitech Media Server again

See post: https://www.henriaanstoot.nl/2014/04/10/portable-squeeze-server/

In the past i’ve used a home build Logitech Squeezebox server (as it was called then), Picore player and tried volumio.
Picore player has been sitting in my livingroom for ages, but was converted to a Node-Red Dashboard and recently Home Assistant Dashboard. (Has been a dasticz daskboard also)

Today i build another version, smaller and with a screen.
Why? .. because of being ‘offline’ or ‘offgrid’ on our holidays.
The car we are driving only has a Aux input.

Most of the installation is as mentioned on:
https://docs.picoreplayer.org/projects/add-a-display/

I edited  /opt/bootsync.sh
to get /dev/sda1 mounted persistent
use pcp br after editing.

Default user/pass : tc piCore

Controlling the thing is via touch or a app on my phone using wifi hotspot.

  • Audio cable 3.5mm
  • Raspberry 3
  • Large usb thumbdrive
  • 3.5inch RPi Display – 480×320 Pixel – XPT2046 Touch Controller
  • car cigarette lighter adapter for power

PiCore uses below alliases

ceChange directory to /mnt/mmcblk0p2/tce
ceoChange directory to /mnt/mmcblk0p2/tce/optional
m1Mount the boot partition /mnt/mmcblk0p1
m2Mount the second partition /mnt/mmcblk0p2
c1Change directory to /mnt/mmcblk0p1
c2Change directory to /mnt/mmcblk0p2
vicfgEdit configuration file config.txt using vi
vicmdEdit boot file cmdline.txt using vi
u1Unmount the boot partition /mnt/mmcblk0p1
u2Unmount the second partition /mnt/mmcblk0p2

Shutting down piCore is done by cutting the power, due to everything being mounted readonly. EXEPT
When you are using LMS server installation, which uses a database.
But there is a tweak for a shutdown button.

I’m using GPIO 16 because i’ve got a screen connected.
Active LOW, means you have to connect a pushbutton/switch between GND and GPIO pin. (nearest Vcc OR Gnd)

Table lamp hack

Added: ino file 20220525

Bought a cheap table lamp a few weeks ago.
Runs on batteries and when you flip it over, it turns on or off.

I thought, when i strip this thing of its internals. I can make a wifi/mqtt enabled one.


Opening it up today, i saw a minimalistic print and a battery holder. There was a tilt switch like

Which i wanted to replace by a mercury one i bought in a bunch of sensors a few years ago.

So why go though all the trouble stripping and replacing .. so i didnt

GND and 5v to the batteries, and D4 to the tilt switch. (Measure which side you have to take!) .. I used a pull down of 3k3 ohms

Esp was flashed in the past with Easy ESP .. well lets keep that one for now.

INO version

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <Ethernet.h>

const char* ssid = "SSID";
const char* password = "PASSWORD";
const char* mqtt_server = "mqttserver";
const char* mqtt_username = "";
const char* mqtt_password = "";
const char* clientID = "wankel";

const int tiltPin = 4;
int tiltState = 0;    
int previousState = 0;    
WiFiClient espClient;

PubSubClient client(espClient);

void reconnect() {
  while (!client.connected()) {
    if (client.connect(clientID, mqtt_username, mqtt_password)) {
    } else {
      delay(2000);
    }
  }
}

void setup()
{
  {
    client.setServer(mqtt_server, 1883);
    pinMode(tiltPin, INPUT);
  }
}
void loop() {
  tiltState = digitalRead(tiltPin);
  if (tiltState != previousState) {
    if (tiltState == HIGH) {
      client.publish("onoff-wankel/wankel/State", "0"); //
    } else {
      client.publish("onoff-wankel/wankel/State", "1"); //
    }
    delay(100);
  }
  previousState = tiltState;

  {
    if (!client.connected()) {
      reconnect();
    }
    client.loop();
  }
}
Node red + led server

Example is using my ledserver, see other post, but i intent to made a easy to configure node red panel where the to be controlled devices are preconfigured.

[
    {
        "id": "9ec21acaec91aecc",
        "type": "mqtt in",
        "z": "54f3b5b461471f2c",
        "name": "",
        "topic": "onoff-wankel/wankel/State",
        "qos": "2",
        "datatype": "auto",
        "broker": "8c74c5f6.9a7a48",
        "nl": false,
        "rap": true,
        "rh": 0,
        "inputs": 0,
        "x": 400,
        "y": 260,
        "wires": [
            [
                "0fe77b535517f818"
            ]
        ]
    },
    {
        "id": "159f65f444a0d7c2",
        "type": "http request",
        "z": "54f3b5b461471f2c",
        "name": "1 - 30 red",
        "method": "GET",
        "ret": "txt",
        "paytoqs": "ignore",
        "url": "http://ledserver:8080/range/01/30/ff0000",
        "tls": "",
        "persist": false,
        "proxy": "",
        "authType": "",
        "senderr": false,
        "credentials": {},
        "x": 900,
        "y": 280,
        "wires": [
            []
        ]
    },
    {
        "id": "5806fbfd0e99daab",
        "type": "http request",
        "z": "54f3b5b461471f2c",
        "name": "1 - 30 black",
        "method": "GET",
        "ret": "txt",
        "paytoqs": "ignore",
        "url": "http://ledserver:8080/range/01/30/000000",
        "tls": "",
        "persist": false,
        "proxy": "",
        "authType": "",
        "senderr": false,
        "credentials": {
            "user": "",
            "password": ""
        },
        "x": 910,
        "y": 220,
        "wires": [
            []
        ]
    },
    {
        "id": "0fe77b535517f818",
        "type": "switch",
        "z": "54f3b5b461471f2c",
        "name": "",
        "property": "payload",
        "propertyType": "msg",
        "rules": [
            {
                "t": "eq",
                "v": "0",
                "vt": "str"
            },
            {
                "t": "eq",
                "v": "1",
                "vt": "str"
            }
        ],
        "checkall": "true",
        "repair": false,
        "outputs": 2,
        "x": 660,
        "y": 260,
        "wires": [
            [
                "5806fbfd0e99daab"
            ],
            [
                "159f65f444a0d7c2"
            ]
        ]
    },
    {
        "id": "8c74c5f6.9a7a48",
        "type": "mqtt-broker",
        "name": "mqttserver",
        "broker": "mqttserver",
        "port": "1883",
        "clientid": "",
        "usetls": false,
        "compatmode": true,
        "keepalive": "15",
        "cleansession": true,
        "birthTopic": "",
        "birthQos": "0",
        "birthPayload": "",
        "closeTopic": "",
        "closePayload": "",
        "willTopic": "",
        "willQos": "0",
        "willPayload": ""
    }
]

ZFS replace disk

I’m using ZFS for my main fileserver, this pool was created over 10 years ago.
Meanwhile i’ve: Swapped broken disks, switched disks for bigger ones and effectively resized my storage 2 or 3 times. Never had any corruption.

Yesterday i say a warning that one of the disks in the pool was OFFLINE.
Today i replaced it using below command’s

  • Put the disk in OFFLINE mode (if needed, mine was already offline)
    • zpool offline tank sdb
  • Remove disk from system
    • echo 1 | sudo tee /sys/block/sdb/device/delete
  • Remove the disk physically
  • Insert the replacement disk. And copy headers/structure from another disk
    • sgdisk –replicate=/dev/sdb /dev/sda
    • sgdisk –randomize-guids /dev/sdb
  • Run the zpool replace command. 
    • zpool replace tank /dev/sdb
  • Use online command to activate disk (no needed in my case, it already did that)
Tips:

# My labels with serials fell off :(
dd if=/dev/sdb of=/dev/null -> blinky led .. 

# What is the serial?
sudo hdparm -i /dev/sdb | grep Serial

Output

root@latex:~# sgdisk --replicate=/dev/sdb /dev/sda
The operation has completed successfully.
root@latex:~# sgdisk --randomize-guids /dev/sdb
The operation has completed successfully.
root@latex:~# zpool replace tank /dev/sdb
root@latex:~# zpool status
  pool: tank
 state: DEGRADED
status: One or more devices is currently being resilvered.  The pool will
        continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
  scan: resilver in progress since Wed May 18 11:31:21 2022
    5.64T scanned out of 14.4T at 331M/s, 7h42m to go
    1.88T resilvered, 39.16% done
config:

        NAME             STATE     READ WRITE CKSUM
        tank             DEGRADED     0     0     0
          raidz1-0       DEGRADED     0     0     0
            sda          ONLINE       0     0     0
            replacing-1  REMOVED      0     0     0
              old        REMOVED      0     0     0
              sdb        ONLINE       0     0     0  (resilvering)
            sdc          ONLINE       0     0     0

errors: No known data errors