stecman

Date/time from GPS without storing NMEA string

This is a first pass at reading the date and time from a serial GPS device on a tiny microcontroller. The target device is an ATTiny13A with only 64 bytes of RAM, which isn't enough to store the full 79 characters of a NMEA sentence, so something like minmea wouldn't work (their API passes around full sentence strings).

When compiled with avr-gcc -Os, this is around 500 bytes of program space. The size can be reduced by 100 bytes if the handling of checksums is removed.

stecman

<?php

use Phalcon\Mvc\Model;

/**
 * Configuration and behaviours for all models
 */
abstract class BaseModel extends Model
{
    /**

stecman

/**
 * Thrown together program to dump 512 kbit EPROMs from an AVR ATMega64A/128A
 * More specifically, a bunch of ST M27C512 from the early 90's
 *
 * Connections:
 *
 *   Port A 0-7: low address byte (output)
 *   Port B 0-7: high address byte (output)
 *   Port D 0-7: data (input)
 *

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#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/wdt.h>

#include <stdlib.h>
#include <string.h>

void init_usart(void)
{
    cli();

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# Show file from Git tree at a certain point in the history
function hist() {
    local ref=$1
    local query=$2

    if [ -z $ref ]; then
        echo "Please specify a ref";
        return;
    fi

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DEVICE = atmega328p
CLOCK  = 16000000
PROGRAMMER = -c arduino -P /dev/ttyUSB0 -b57600

AVRDUDE = avrdude $(PROGRAMMER) -p $(DEVICE)

SOURCES = $(shell find . -name '*.c')
OBJECTS = $(SOURCES:.c=.o)

# Automatic dependency resolution

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import os

# Device definition for the stm8s.h header
# This enables available features of the device library.
STM8_DEVICE_DEFINE = "STM8S003"

# Programmer argument for stm8flash (stlink or stlinkv2)
STM8_PROGRAMMER = "stlinkv2"

# Target device argument for stm8flash

stecman

AVR C 1-Wire + DS18B20 temperature sensor

This implements Maxim's One Wire / 1-Wire protocol for AVR microcontrollers from the DS18B20 datasheet and Maxim's other application notes.

Usage

Single DS18B20 device on bus

With just one DS18B20 on the 1-Wire bus, you can ignore slave addresses:

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SCons + SDCC for STM8S

Setting up SCons to build using SDCC was fairly time consuming for someone new to SCons, so here's a basic working config to get you started.

With some tweaking this should also work for other architectures that SDCC supports (z80, z180, mcs51, r2k, etc).

Required software

SCons (build tool)

stecman

Controlling the Brother P-Touch Cube label maker from a computer

The Brother PTP300BT label maker is intended to be controlled using the official Brother P-Touch Design & Print iOS/Android app. The app has arbitrary limits on what you can print (1 text object and up to 3 preset icons), so I thought it would be a fun challenge to reverse engineer the protocol to print whatever I wanted.

Python code at the bottom if you want to skip the fine details.

Process

Intitially I had a quick peek at the Android APK to see if there was any useful information inside. The code that handles the communication with the printer in Print&Design turned out to be a native library, but the app clearly prepares a bitmap image and passes it to this native library for printing. Bitmaps are definitely something we can work with.