Post by thread:Port expander (more I/O pin)

Hi Giorgio First of all this is NOT [OT], so I removed that classifier from the sub ject. I think you might consider using external registers (latches), probably even shift registers because you might want to send data in serial mode, it will save several i/o pins when compared to paralel mode. At 19:24 98.03.02 +0100, you wrote: {Quote hidden}>In my project I need many I/O pin. There is some chip than can expand the >digital I/O PIC capacity? I found a Elan Microeletronics chip that have a >I2C input and 14 digital output (EM83010). There is something similar with >more pin and of another producer? >Thanks in advantage. > > >=================================================== >Alboni Giorgio >Faenza (Ra) ITALY >E-Mail: spam_OUTrac1337TakeThisOuTracine.ravenna.it > >www.geocities.com/SiliconValley/Heights/5444 >(Last Update: 29/09/97) >=================================================== > =============================================================== cumprimentos / best regards Jorge Ferreira //.....jorgegfKILLspam@spam@mail.telepac.pt ------ Make sure brain is in gear before engaging mouth ------- ===============================================================

Try Intel 8243 I/O Expander. It has 4bit interface (needs total of 5 I/O lines) and provides 16 I/O lines (4bit x 4). 24pin DIP package. At 07:24 PM 3/2/98 +0100, Alboni Giorgio wrote: >In my project I need many I/O pin. There is some chip than can expand the >digital I/O PIC capacity? I found a Elan Microeletronics chip that have a >I2C input and 14 digital output (EM83010). There is something similar with >more pin and of another producer? > Ranna M. V. Consultant Engineer NEURON SYSTEMS 4/77, 13th Main Road Tel/Fax:+91-80-529 6071 HAL 2nd Stage Email: rannaKILLspamblr.vsnl.net.in Bangalore 560 008, INDIA

I would suggest using 74HC165's (eight inputs each) and 74HC595's (eight outputs each); you can add any amount of I/O using only three or four port pins total. Further, unlike the 74HC164 that others have suggested, the 74HC595 includes output latches so the outputs will not glitch while the data are being shifted; it also includes a global output-enable signal and asynchronous reset. To wire the devices, you should tie the shift clock wires of all devices to one port pin and the load/latch wires to a second pin. The data-in from one of the 595's should be connected to a port pin; its data out should feed the next part's data-in, etc. until the last part's data-out either feeds another port pin or else goes through a 1K resistor into the pin that's used for the PIC's output data. The one caveat with this method is that any time you want to change any of the outputs or read any of the inputs, you'll have to do them all. You should thus plan carefully what devices you place on the shifters and what ones you put on the "high speed" port pins of the PIC itself. Still, I have used this method quite effectively on a system with 32 inputs and 32 outputs and found it more convenient than just about anything else (although I2C devices may allow you to update some data without rewriting everything, the extra overhead of the I2C protocol may largely negate this advantage). One other type of port expansion produced by Dallas Semiconductor that I'll mention because it's cute (whether it's practical is another question) is their one-wire-interface I/O port. It's a little TO-92 which can read or ground (open-collector) one I/O pin. It hangs on Dallas's one-wire bus and thousands of them could be controlled individually with a single port pin. Note sure if it's useful in many applications, but certainly cute.

At 08.18 03/03/98 -0500, you wrote: >Where can I find information on this Elan Microelectronics Chip. I >looked for them on the web. Didn't have any luck there. There is >another I2C chip by Phillips but it is only 8 I/O. I believe it is the >PCF 8574. Please pass along any info on this Elan chip. Thanks > >DW > I don't now if there is some information of Elan Microelectronics corp. on the web. I found some information on a journal (in advertisement of ESCO, a italian elettronics seller, see: http://www.gen.com/escocetri). The EM 83010 is a port expander in a 18 pin package, you can connect up to 8 device on the same I2C line. For me when you connect more EM 83010 on the same I2C line the I/O pin decrease to 11 (3 pin for device address) but I'm not sure. The EMC (Elan Microelectronics corp) make some CPU that are pin compatible with PIC (EM78XXX). Bye. =================================================== Alboni Giorgio Faenza (Ra) ITALY E-Mail: .....rac1337KILLspam.....racine.ravenna.it www.geocities.com/SiliconValley/Heights/5444 (Last Update: 29/09/97) ===================================================