MAX7219 LED display driver for ESP8266

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Here is an Instructable on writing a MAX7219 driver for interfacing an 8-digit seven segment LED to ESP8266 platform. The MAX7219 are compact, serial input/output common-cathode display drivers that interface microprocessors (µPs) to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDs. Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and an 8×8 static RAM that stores each digit. Only one external resistor is required to set the segment current for all LEDs. A convenient 4-wire serial interface connects to all common µPs. Individual digits may be addressed

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555 Timer as power usage sensor

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Electricity meters usually have blinking LED lights whose flashing rate is associated with the amount of energy usage. This example shows how to use a 555 timer chip acting as Schmitt trigger combined with a phototransistor or LDR to sense the flashing LED on the electricity meter for monitoring electricity usage. The output of the 555 timer chip is connected to one of the GPIO pins on the Raspberry Pi. A Python script (executing in the background) recording 555 events is calculating actual energy usage [e.g. Watt] every time the 555 is signaling and stores epochs in an SQLite3 database. From this, another

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ESP8266 MP3 decoder

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This Github upload shows an example of how to use the I2S module inside the ESP8266 to output sound. In this case, it is used to output decoded MP3 data (actually, more accurately: MPEG2 layer III data): the code described here basically is a webradio streamer which can connect to an Icecast server, take the MP3 data the server sends out, decode it and output it over the I2S bus to a DAC. The MP3 decoder has been tested for bitrates up to 320KBit/s and sample rates of up to 48KHz. The biggest part of this code consists of a

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Hacking a bathroom weighscale for cloud connectivity

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Hardware hacker Darrel Tan has a great write-up about his experience with hacking a Chinese-made bathroom scale for cloud connectivity using a Raspberry Pi. His bathroom weighscale has a separate display part that receves the weight measurements from the scale through an infrared link. Darrel hooked up an 38kHz IR receiver to the logic analyzer and placed it near the scale as he was standing on it, so that he could decode the IR bursts. He found that the device used pulse distance coding to encode the data with ~75ms spacing between the consecutive bursts. With further analysis, he was able to figure

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ATtiny85 based mini weather station

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This Instructable describes a mini weather station using ATtiny85 and DHT11 sensor. It consists of TX and RX units with a 433MHz RF link to connect them. The TX unit sends temperature and humidity measurements to RF module, which then displays the data on an LCD. In a recent instructable Indigod0g described a mini weather station that works pretty well, using two Arduinos. Maybe not everyone wants to sacrifice 2 Arduinos to get humidity and temperature readings and I commented that it should be possible to do a similar function with two Attiny85’s. I guess talk is easy, so I better put

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