Electronics on csegura

Changing the SGI Octane’s Light-Bar LEDs

Sun, 25 Oct 2026 00:00:00 +0000

A small change to an SGI workstation

I changed the indicator LEDs in my SGI Octane’s light bar. I chose blue LEDs and added two resistors to keep their current within a safe range.

The light bar is a narrow assembly in the front of the case. Its lights make the computer’s status visible from the outside. I wanted to replace the dead lights and give them a blue glow.

NorthStar Advantage Restoration Part 1

Sun, 25 Oct 2026 00:00:00 +0000

A restoration that took more than a year

I bought this NorthStar Advantage on Wallapop in 2024. The seller told me that the keyboard had a fault. But at power-on, the computer still displayed a message on the screen. As always trust in the seller’s words, was an act of faith.

Indeed, buying vintage computers is always a bit of a gamble but be prepared for surprises when dealing with vintage hardware.

Fixing Sharp MZ-700

Fri, 23 Aug 2024 00:00:00 +0000

Fixing Sharp MZ-700

Time to fix the Sharp MZ-700, I have this computer for a while, and it was not working. I decided to fix it. I opened the computer and I found that the power supply was not working correctly. I decided to do the standard procedure, replaced suspects capacitors and voltage regulators. Here are some pictures of the process:

This machine was manufactured in 1982, and it was a very popular computer in Japan. It was used in schools and homes. It has a Z80 CPU, 16KB of RAM, and 16KB of ROM. It has a built-in tape recorder, and it can display 40x24 characters in 8 colors.

ISA-PicoMem

Wed, 05 Jun 2024 00:00:00 +0000

I’m restoring this wonderful IBM XT 5150, machine powered up, but there wasn’t os. Floppy drive was`t working, I tried to boot from a 720k floppy disk, but it was impossible. So looking for a solution, I found a ISA-PicoMem (https://github.com/FreddyVRetro/ISA-PicoMEM/tree/main) card, a wonderful card that allows you to boot from a SD card, add memory, and is able to connect to a network using wifi and ne2000 drivers, of course you need install mTCP.

Connecting a Z80 to a Raspberry Pi

Mon, 18 Mar 2024 00:00:00 +0000

I have a long history with computers, starting with a Sinclair Zx81 that I still own, followed by other models and others that I wished for, as time went by.

A while back, I found an old box with some old processors, x386, x486, a few Pentiums first generation and two Zilog Z80. Then I got a kind of retro-feeling in my mind and I watched some YouTube videos about them. One of them was the classic nop-test, I had fun with this for a whole afternoon.

Fixing Dragon 32 Power supply

Sat, 16 Mar 2024 00:00:00 +0000

This morning the Dragon 32 power supply broke. I have a Dragon 32 that I bought one time ago. But when I tried to turn it on, it didn’t work. I checked the power circuit inside of the Dragon 32 and found that the regulator was broken.

It was a LM340T 7812, 12v regulator, so I replaced it with a new one. But when I tried to turn it on, it didn’t work.

Arduino car

Tue, 01 Nov 2011 00:00:00 +0100

I have been working on a project that involves controlling a car with an Arduino board. The car is made of a chassis, two motors, and a battery. The motors are connected to the Arduino board through a motor driver, which allows the Arduino to control the speed and direction of the motors using a wii nunchuck as a remote control.

#include <math.h>
#include "Wire.h"
#include "WiiChuck.h"
#include <Servo.h>
#include <RHMotor.h>

WiiChuck chuck = WiiChuck();

int joyX = 0;
int joyY = 0;

#define MOVING_MARGIN 50
#define ROTATE_MARGIN 50

int left_motor_pin = 7;
int right_motor_pin = 6;

RHMotor motor(left_motor_pin, right_motor_pin);

void setup()
{

 Serial.begin(9600);
 Serial.flush();

 Serial.println("Initialize chuck engine.");

 chuck.begin(1000);
 chuck.update();

 delay(1000);

 Serial.println("Completed.");
 Serial.println("Initialize motor engine.");

 motor.start(300);

 delay(1000);
 motor.stop();

 Serial.println("Completed.");
}

void loop()
{

 chuck.update();

 joyX = chuck.readJoyX();
 joyY = chuck.readJoyY();
 //Serial.print(joyX);
 //Serial.print(" ");
 //Serial.print(joyY);
 //Serial.println();

 if (millis()%1000 == 0)
 Serial.print(".");

 if (chuck.zPress() == 1) {
 Serial.println("Z Pressed");
 motor.stop();
 }

 if (joyY > MOVING_MARGIN) {
 Serial.println("Fwd");
 motor.forward();
 } else if (joyY < 0-MOVING_MARGIN) {
 Serial.println("Bwd");
 motor.backward();
 }

 if (joyX > ROTATE_MARGIN){
 Serial.println("Right");
 motor.right(300);
 } else if (joyX < 0-ROTATE_MARGIN) { 
 Serial.println("Left"); 
 motor.left(300);
 }

 if (chuck.cPress()) {
 int left = motor.getLeftServo().readMicroseconds();
 int right = motor.getRightServo().readMicroseconds();
 Serial.print(left);
 Serial.print(" ");
 Serial.println(right);
 }

 joyX = 0;
 joyY = 0;

 delay(20);
}

This is a sort video of the car in action:

Servo calibration

Tue, 01 Nov 2011 00:00:00 +0100

Este experimento es para tratar de calibrar los servos que se van a usar como motores.

Este paso es importante ya que hay que encontrar el punto en el que el servo queda detenido.

Material -Un servo de rotación continua

Conexiones - Usar para el servo una salida con PWM

#include <Servo.h>
#define SERVO_PIN 6

Servo servo;
int velocity;
void setup()
{

 Serial.begin(9600);
 Serial.flush();

 // Initialize
 velocity = 0;

 servo.attach(SERVO_PIN);
}

void loop()
{
 // commands
 if ( Serial.available()) {
 char ch = Serial.read();
 switch(ch) {
 case 's':
 servo.write(0);
 servo.write(velocity);
 break;

 case 'a':
 velocity += 10;
 break; 
 case 'd':
 velocity -= 10;
 break; 
 case 'z':
 velocity += 1;
 break; 
 case 'x':
 velocity -= 1;
 break; 
 case 'f':
 servo.detach();
 servo.attach(SERVO_PIN);
 break;
 case 'q':
 velocity = 0;
 servo.write(velocity);
 break;
 case 'w':
 velocity = 90;
 servo.write(velocity);
 break;
 case 'e':
 velocity = 180;
 servo.write(velocity);
 break; 
 }
 Serial.print("> ");
 Serial.print(ch);
 Serial.print(" ");
 Serial.print(velocity);
 Serial.print(" ");
 Serial.print(servo.readMicroseconds());
 Serial.println();
 }
}

Resultados

Servo A

Stop 86 (momento en que el servo deja de meter ruidito)

Servo B

Stop 83

GPS Arduino

Tue, 05 Apr 2011 00:00:00 +0100

La cosa es que en cierta ocasión había abierto este GPS y me había llamado la atención los agujeritos de conexión que hay dentro, de modo que me puse a buscar información al respecto y di con esta página (de un tal xam) en la que vi una foto en donde se actualizaba el software por medio de los agujeritos… http://xamweb2.dyndns.org/wordpress/2008/02/20/fortuna-clipon-flashing/ http://xamweb2.dyndns.org/wordpress/2007/09/20/innenleben-von-sirf2-gps-mausen-2/

Información

Mi GPS es parecido al de la primera foto pero distin del de la segunda, en vez de tener 12 agujeritos tiene 7

C64 Arduino

Fri, 01 Apr 2011 00:00:00 +0100

He intentado encontrar el código pero no hay forma ..

Arduino LC24XX EPROM (paginated 2)

Fri, 04 Mar 2011 00:00:00 +0100

Finalmente he hecho una biblioteca I2C_eeprom. Hay una parte que merece una explicación es el hecho de que estas memorias EEPROM tienen un modo de escritura más rápida (Page Write), en este modo podemos escribir 64bytes de golpe con lo que el proceso de escritura es considerablemente más rápido. Este modo viene explicado en el datasheet de estas eeproms. La cosa es que cuando he ido a implementarlo he tenido bastantes problemas. Lo que he estado programando usa la biblioteca Wire, que a su vez usa unas funciones definidas en Wire\Utility\Twi.h (Two Wire Interface??) Bien, tanto Wire como Twi usan un buffer interno de 32bytes, y el 24lc256 usa páginas internas de 64bytes, de modo que hay que ajustar estas dos bibliotecas para poder usar el método write_bytes_fast otra cosa importante es que este método no es capaz de saltar de dispositivo, así que estamos limitados a 32k, más que suficiente. La segunda cosa es que los bloques de 64 bytes deben escribirse completamente, es decir que en cada operación no se pueden escribir ni más ni menos y deben escribirse en su sitio. En 32k hay 512 páginas de 64bytes. Nota: para usar fast hay que modificar el tamaño del buffer en wire.h y twi.h pero en ambas hay que usar un buffer de 66Bytes, esto es debido a que el direccionamiento previo son dos Bytes.

Arduino LC24XX EPROM

Thu, 03 Mar 2011 00:00:00 +0100

Código

El código que amplia la biblioteca Wire para usar EEPROMs 24lcXX http://www.arduino.cc/playground/Code/I2CEEPROM

La biblioteca Wire http://arduino.cc/en/Reference/Wire

#include <Wire.h>
void I2C_eeprom_write_byte( int deviceAddress, unsigned int address, byte data )
{
 int rdata = data;
 Wire.beginTransmission(deviceAddress);
 Wire.send((int)(address >> 8)); // MSB
 Wire.send((int)(address & 0xFF)); // LSB
 Wire.send(rdata);
 Wire.endTransmission();
 delay(10);
}
void I2C_eeprom_write_page( int deviceAddress, unsigned int addressPage, byte* data, byte length )
{
 Wire.beginTransmission(deviceAddress);
 Wire.send((int)(addressPage >> 8)); // MSB
 Wire.send((int)(addressPage & 0xFF)); // LSB
 byte c;
 for ( c = 0; c < length; c++)
 Wire.send(data[c]);
 Wire.endTransmission();
}
byte I2C_eeprom_read_byte( int deviceAddress, unsigned int address )
{
 byte rdata = 0xFF;
 Wire.beginTransmission(deviceAddress);
 Wire.send((int)(address >> 8)); // MSB
 Wire.send((int)(address & 0xFF)); // LSB
 Wire.endTransmission();
 Wire.requestFrom(deviceAddress,1);
 if (Wire.available()) rdata = Wire.receive();
 return rdata;
}
void I2C_eeprom_read_buffer( int deviceAddress, unsigned int address, byte *buffer, int length )
{
 Wire.beginTransmission(deviceAddress);
 Wire.send((int)(address >> 8)); // MSB
 Wire.send((int)(address & 0xFF)); // LSB
 Wire.endTransmission();
 Wire.requestFrom(deviceAddress,length);
 int c = 0;
 for ( c = 0; c < length; c++ )
 if (Wire.available()) buffer[c] = Wire.receive();
} 
//*************************************************************************************************
static void DumpHex(int deviceAddress, unsigned long startAddress, unsigned long endAddress)
{
 int value;
 int lineCounter;
 char textBuffer[24];
 unsigned long address;
 
 lineCounter = 0;
 address = startAddress;
 
 while (address < endAddress)
 {
 sprintf(textBuffer, "0x%05X - ", address);
 Serial.print(textBuffer);
 sprintf(textBuffer, "0x%05X - ", address + (endAddress - startAddress));
 Serial.print(textBuffer);
 textBuffer[0] = 0;
 
 for (int dumpCounter=0; dumpCounter<16; dumpCounter++)
 {
 value = I2C_eeprom_read_byte(deviceAddress,address);
 
 Serial.print(value,HEX);
 Serial.print(" ");
 
 if ((value >= 0x20) && (value < 0x7f))
 {
 textBuffer[dumpCounter % 16] = value;
 }
 else
 {
 textBuffer[dumpCounter % 16] = '.';
 }
 
 address++;
 }
 
 textBuffer[16] = 0; 
 Serial.println(textBuffer); 
 }
}
void I2C_eeprom_delete(int deviceAddress, unsigned long startAddress, unsigned long endAddress)
{ 
 for(unsigned long address=startAddress; address < endAddress + 1; address++) {
 if (I2C_eeprom_read_byte(deviceAddress,address) != 0xFF)
 {
 Serial.println(address,HEX);
 I2C_eeprom_write_byte(deviceAddress,address,0xFF);
 }
 }
}
#define EEPROM_DEVICE 0x50
#define EEPROM_INIT 0x00000
#define EEPROM_END 0x08000
void setup()
{
 
 Wire.begin();
 Serial.begin(9600);
 
 long ms;
 
 Serial.println("Deleting..");
 ms = millis();
 I2C_eeprom_delete(EEPROM_DEVICE,EEPROM_INIT,EEPROM_END);
 Serial.print(millis()-ms);
 Serial.println("ms");
 
 Serial.println("---- Dump ---");
 
 DumpHex(EEPROM_DEVICE,EEPROM_INIT,EEPROM_INIT+0x0f); 
 DumpHex(EEPROM_DEVICE,EEPROM_END-0x0f,EEPROM_END); 
 
 Serial.println("---- Write at begin ---");
 
 DumpHex(EEPROM_DEVICE,EEPROM_INIT,EEPROM_INIT+0x0f); 
 Serial.println("Writing...");
 I2C_eeprom_write_byte(EEPROM_DEVICE,EEPROM_INIT,0xCC);
 I2C_eeprom_write_byte(EEPROM_DEVICE,EEPROM_INIT+0x0f,0xCC);
 DumpHex(EEPROM_DEVICE,EEPROM_INIT,EEPROM_INIT+0x0f);
 Serial.println("---- Writte at end ---");
 DumpHex(EEPROM_DEVICE,EEPROM_END-0x0F,EEPROM_END); 
 Serial.println("Writing...");
 I2C_eeprom_write_byte(EEPROM_DEVICE,EEPROM_END,0xCC);
 I2C_eeprom_write_byte(EEPROM_DEVICE,EEPROM_END-0x0f,0xCC);
 DumpHex(EEPROM_DEVICE,EEPROM_END-0x0f,EEPROM_END); 
 
 Serial.println("---- end ---"); 
 
 //DumpHex(EEPROM_DEVICE,EEPROM_INIT,EEPROM_INIT+0x0f);
 //DumpHex(EEPROM_DEVICE,EEPROM_END-0x0f,EEPROM_END); 
}
void loop()
{
}

He añadido l2C_eeprom_delete para borrar la eeprom, . Tambien he añadido un delay(5) tras cada operación de escritura debido a que si no, no me escribia bien.

Arduino LC24XX EPROM (paginated)

Thu, 03 Mar 2011 00:00:00 +0100

Habia algunas cosas que no me cuadraban …

Lógico.

Con la biblioteca actual Wire y las funciones I2C_eeprom de (http://www.arduino.cc/playground/Code/I2CEEPROM) .. me he dado cuenta de que las direciones van en un entero (int) que en arduino, son 2 Bytes (16 bits) y con eso no podemos escribir más alla de los 64k, de modo que he cambiaod el código para usar un sistema de páginación.

Por ejemplo con 4 24lc256 tendriamos 4 páginas de 32k lo resumo en estas dos funciones

Fonera ser2net

Thu, 03 Feb 2011 00:00:00 +0100

He tenido muchos problemas y no he conseguido hacer funcionar el ipkg correctamente en la fonera, creo que es un problema de rutas .. al final he hecho una serie de inventos.

cada vez que me ejecuto el “ipkg update” me dan estos errores

ERROR: File not found: //usr/local/lib/ipkg/lists/whiterussian
 You probably want to run `ipkg update'
ERROR: File not found: //usr/local/lib/ipkg/lists/non-free
 You probably want to run `ipkg update'
ERROR: File not found: //usr/local/lib/ipkg/lists/backports
 You probably want to run `ipkg update'

en mi ddwrt no hay /usr/local/lib y no puedo crearlo

Fonera Kamikaze

Wed, 02 Feb 2011 00:00:00 +0100

Notas de la instalación

descargar de http://downloads.openwrt.org/kamikaze/8.09/atheros/

openwrt-atheros-vmlinux.lzma
openwrt-atheros-root.squashfs

entrar por serie al redBoot

RedBoot(tm) bootstrap and debug environment [ROMRAM]
Non-certified release, version V1.00 - built 10:37:27, Dec 12 2006
Copyright (C) 2000, 2001, 2002, 2003, 2004 Red Hat, Inc.
Board: FON1
RAM: 0x80000000-0x81000000, [0x80040aa0-0x80fe1000] available
FLASH: 0xa8000000 - 0xa87f0000, 128 blocks of 0x00010000 bytes each.
== Executing boot script in 5.000 seconds - enter ^C to abort
^C
RedBoot> ip_address -l 192.168.1.254/24 -h 192.168.1.5
IP: 192.168.1.254/255.255.255.0, Gateway: 0.0.0.0
Default server: 192.168.1.5
RedBoot> fis init
About to initialize [format] FLASH image system - continue (y/n)? y

*** Initialize FLASH Image System
... Erase from 0xa87e0000-0xa87f0000: .
... Program from 0x80ff0000-0x81000000 at 0xa87e0000: .

RedBoot> load -r -b %{FREEMEMLO} openwrt-atheros-vmlinux.lzma
Using default protocol (TFTP)
Raw file loaded 0x80040c00-0x80100bff, assumed entry at 0x80040c00
RedBoot> fis create -e 0x80041000 -r 0x80041000 vmlinux
... Erase from 0xa8030000-0xa80f0000: ............
... Program from 0x80040c00-0x80100c00 at 0xa8030000: ............
... Erase from 0xa87e0000-0xa87f0000: .
... Program from 0x80ff0000-0x81000000 at 0xa87e0000: .
RedBoot> load -r -b %{FREEMEMLO} openwrt-atheros-root.squashfs
Using default protocol (TFTP)
Raw file loaded 0x80040c00-0x801e0bff, assumed entry at 0x80040c00
RedBoot> fis free
 0xA80F0000 .. 0xA87E0000
RedBoot> fis create -l 0x6f0000 rootfs
... Erase from 0xa80f0000-0xa87e0000: ..........................................................................
... Program from 0x80040c00-0x801e0c00 at 0xa80f0000: ..........................
... Erase from 0xa87e0000-0xa87f0000: .
... Program from 0x80ff0000-0x81000000 at 0xa87e0000: .
RedBoot> fconfig
Run script at boot: true
Boot script:
.. fis load -l linux
.. exec
Enter script, terminate with empty line

>> fis load -l vmlinux
>> exec
>>

Boot script timeout (1000ms resolution): 5
Use BOOTP for network configuration: false
Gateway IP address:

Local IP address: 192.168.1.1
Local IP address mask: 255.255.255.0
Default server IP address: 192.168.1.254
Console baud rate: 9600
GDB connection port: 9000
Force console for special debug messages: false
Network debug at boot time: false
Update RedBoot non-volatile configuration - continue (y/n)? y
... Erase from 0xa87e0000-0xa87f0000: .
... Program from 0x80ff0000-0x81000000 at 0xa87e0000: .
RedBoot>

Nota*

Fonera Serial

Wed, 02 Feb 2011 00:00:00 +0100

Borrar la nvram

mtd -r erase nvram

Configuración Wan - disabled STP - enabled

Configurar el wireles con el mismo ssid que el router de casa En security asignar los permisos En el setup básico darle una IP de las de casa

Recovery

Como la fonera esta estropeada he tenido que hacer un recovery ..

Para empezar la he conectado al arduino, así puedo usar el terminal (terraterm) para acceder al RedBoot

Fonera Serial

Tue, 01 Feb 2011 00:00:00 +0100

Material - Un router la fonera.

Código Una vez establecidas las conexiones usando el terminal pordemos acceder al puerto serie de la fonera via el arduino.

He instalado el openWrt Instalando openWrt Kamikaze (me ha gustado más que el ddwrt) ademas me deja casi 4Mb libres en la memoria de la fonera y he instalado algunos paquetes que me han interesado.

Aunque he estado enredando con el el ser2net (ser2net) al final he optado por el netcat, me explico.