Glolab ED4GP Encoder / Decoder
The Glolab ED4GP microprocessor based Encoder / Decoder is designed for use with wireless modules, infrared remote controls and other devices that operate with serial input and output data. It can be used as either an encoder or a decoder by simply connecting pin 3 either low to VSS for an encoder or high to VDD for a decoder. It can encode or decode four bits of data and four address bits (16 addresses).
When used as an encoder the encoding of data is initiated by a any or all input pins going low. When used as a decoder, either momentary or latched data outputs can be selected by connecting pin 12 either high or low. A momentary valid transmit output indicates when valid data is being received.
When not encoding or decoding, the ED4GP remains in a low power mode where it draws only 1 microampere making it ideal for battery powered applications. It is powered by 5 volts and draws about 3.5 milliamperes not including loads, when active. As an encoder it becomes active when an input pin is pulled low. As a decoder it becomes active when it receives serial data.
An internal clock is generated by a 4 MHz ceramic resonator connected to pins 15 and 16 which provides accurate frequency control and therefore better serial data synchronization than the resistor controlled oscillators used in some encoders and decoders. This allows higher speed data transfer without the risk of lost data. A resonator of the type that has three pins and contains internal capacitors to minimize components is recommended for oscillator frequency control. 4 MHz Resonators are available from Digi-Key, ECS p/n X902, Panasonic p/n PX400 and Mouser, ECS p/n 520-ZTT400MG and from Glolab p/n CR4. The ED4GP can be powered with 5 volts from a battery or other power source. One ED4GP and one CR4 are required for each encoder application. Another ED4GP and CR4 are required for each decoder application.
The following schematic shows a basic wireless RF transmitter application circuit with the ED4GP used as an encoder.
The four address pins can be connected to pin 2 through switches, logic circuits or other devices
All data in pins are pulled up to VDD by internal 200 microampere current sources and they are active low. A low level on any or all data in pins will initiate a transmit sequence and will produce a high level on the serial output. The internal pullups in combination with active low for each data in pin is convenient for use with push button switch inputs.
The serial output generated at pin 18 when a transmit sequence is initiated consists of two bytes. The first byte contains the address bits that have been selected by the encoder address pins and the second byte contains the four data bits. The bytes are automatically sent at least two times (one packet) when a transmit sequence is started regardless of how short a time transmit is enabled. Transmission of packets will repeat as long as transmit is enabled. A packet is sent in 20 milliseconds.
A light emitting diode with a 470 ohm series current limiting resistor can be connected to pin 1 and to VSS. It will light to indicate that a transmission is taking place.
The following schematic shows a basic wireless receiver application circuit with the ED4GP used as a decoder.
Latched outputs can be selected by connecting pin 12 to pin 10. Momentary outputs are selected by leaving pin 12 open.
The packets of serial output generated by the transmitter encoder and sent to the receiver decoder by wireless, infra red or other means are fed into serial input pin 11 of the decoder. A packet is stored and the address bytes within it are compared with those of the decoder address pin settings. If the addresses match then the data is passed to the output pins. Each of the output pins can both source and sink 25 milliamperes.
The ED4GP is not code compatible with the GL-104.
DOWNLOAD a ED4GP data manual including application circuits, in PDF format
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