Interfacing 64-INPUTS to 8051

[Santosh13]

Hi all,
I want to interface 64 inputs to an micro-controller(8051) for example just like FAULT INDICATION.
Can anyone please suggest what type of switching can be used to multiplex the inputs that can be feed into the micro-controller ?

Note :
1) Its not an keypad interface.
2) I should be able to identify the faulty device and display on the 16*2 LCD screen using 'C' code...

Thanks in advance !

 

[srizbf]

have three 8255s for your job.

connect all output from 8255
to a port(p0).
connect each a0 and a1 line of each 8255 to p1 individual lines.

connect chipselect of 8255 fro each line of other port bits.

now as like programming 8255 you can select each 8255 separately and read any one of 64 inputs.

 

[bigdogguru]

Another possible option is the use of I2C or SPI port expanders. Several manufacturers produce them, TI, Atmel, MAXIM and Microchip to name a few.

You may want to consider the MCP23017 or MCP23018 16-bit I2C Port Expanders from Microchip:

MCP23017

MCP23017
16-bit input/output port expander with interrupt output
Cascadable for up to 8 devices on one bus
25mA sink/source capability per I/O
Supports 100kHz, 400kHz and 1.7MHz I2C™Compatible compatible modes
Device Description 16-bit I/O Port Expander
Operating Voltage Range (V) 1.8 to 5.5
Operating Temp Range (°C) -40 to 125
Interface I²C™
Max. Bus Frequency (kBits/s) 1700

MCP23018

MCP23018 is a 16-bit I/O expander for high speed I2C™Compatible interface.
16-bit remote bidirectional I/O port
Open-drain outputs: - 5.5V tolerant - 25 mA sink capable - 400 mA total current out
High-speed I2C™ interface up to 3.4 MHz
Single hardware address pin: Voltage input to allow up to eight devices on the bus
Configurable interrupt output pins: active-high, active-low or open-drain
Low standby current:1 μA (typ.)
Device Description 16-bit I/O Port Expander
Operating Voltage Range (V) 1.8 to 5.5
Operating Temp Range (°C) -40 to 125
Interface I²C™
Max. Bus Frequency (kBits/s) 3400

Four MCP23017/MCP23018 will give you the required 64 inputs and require only two pins from the 8051 for the I2C interface, depending on your 8051 variant, you may already have a hardware I2C interface available. Both versions also offer interrupt lines to trigger an interrupt routine on your 8051, for example a "FAULT INDICATION."

BigDog

 

[andre_luis]

I usually had used a set of 74HCT373 devices to perform reading of inputs amount greater than avaliable on uC.
Check if scan rate reduction could be a problem at your application.

+++

 

[aashitech]

Dear,
You can also use 8 numbers of "8-bit parallel-in/serial-out shift register" 74HC165..they are cheapest and most suitable option... i once used them to get information of 500 + photo sensors status ... system was Leather Area measuring Machine used in leather tannery to measure skins dimensions in 2D.

 

[HTA]

For industrial I/O with error identication (like shorted or open signal line) you can check-out also the iC-JX from iC-Haus(iC-Haus Homepage - product: iC-JX ). It has 16-I/O ports with 24V input capability, both digital and analog. Readout is via SPI.