Need more then 15 I/O pins

lindseydallas

Is there a way to put multiple Basic Stamp modules in parallel or similarly linked so that you can have more than 15 I/O pins controlled by the same program? I am planning to use the Basic Stamp as a PLC with up to 4 analog inputs (from A2D converters), 1 digital input, 5 digital outputs, plus I want to include a display and keypad. I would also like to power some LEDs based on the on/off status of some of the pins… Basically I need more than 15 I/O pins to make this all work. I would like to stick with the Basic Stamp since I’ve put a lot of time into the tutorials. However, if that is not possible I would be open to other options. Thanks for any advice!

davejames

Hello Lindsey and welcome to the Forum!

Two possible ideas come to mind:
1) use shift registers anywhere you can to reduce the number of pins in/out of the Stamp.
2) take a look at this product: http://www.parallax.com/product/bs2p40

Some will also suggest moving to the Propeller device, which will entail another learning curve.

lindseydallas

The BS 2p40 looks like it would solve my problem nicely! Sorry I did not see that one before posting.

Thanks for the quick reply!

Ron Czapala

You might want to look into using I/O expanders like the MCP23017 (I2C) or MCP23S17 (SPI) or others. Not sure how well they work with ADC chips but they should handle any digital devices like displays and keypads.

davejames

lindseydallas wrote: »

The BS 2p40 looks like it would solve my problem nicely! Sorry I did not see that one before posting.

Thanks for the quick reply!

...welcome and good success to you. :thumb:

WBA Consulting

lindseydallas, welcome to the forums! I will second DaveJames' suggestion of the BS2P40 as I have used them to solve your exact dilemma. One thing to take note of that seems to catch quite a few people is how to use the second set of 16 IO pins. Check out this thread and make sure you pay close attention to how the IO pins are mapped out on the chip itself.

http://forums.parallax.com/showthread.php/110403-BASIC-Stamp-2P-40-Help!?highlight=bs2p40+auxio

erco

lindseydallas: Welcome to the forums.

Pity you didn't ask your question last Monday... http://forums.parallax.com/showthread.php/150422-Half-Price-45-BS2P40

Ron Czapala

Well you can certainly use a $89 BS2P40 although it won't fit in any of the Parallax carrier boards or get a MCP23017 for $1.44 (and cascade multiple one togeher if need be).

If I already had a BS2. I would get the I/O expander and save $87 or get a Propeller board with 32 pins.

Tracy Allen

You can also save pins by using modules such as the 27977 serial LCD display from Parallax. There are similar items for buttons and keypads, and they can add intelligence for scanning too, which takes a burden off of the PBASIC coding required.

erco

Tracy Allen wrote: »

You can also save pins by using modules such as the 27977 serial LCD display from Parallax. There are similar items for buttons and keypads, and they can add intelligence for scanning too, which takes a burden off of the PBASIC coding required.

If you run NOW, you might be able to find that $30 LCD which Tracy mentioned on closeout for $5 at Radio Shack. But the insider scoop is that none of these clearance items will available after Sunday.

http://www.radioshack.com/product/index.jsp?productId=12296090

If you go to a Shack, read this other thread to see what other heavily discounted treasures you can look for: http://forums.parallax.com/showthread.php/149327-RadioShack-Pushes-to-Clear-Inventory/page3