Cheapest way to get going

[dncky]

Im whipping up a new project and Im having a hard time deciding how to go with it.

I dont need anything super specific, about 16 IO pins is all I need. In that vein, Ive been looking at some 20 pin DIP msp430 with the BSL functionality for programming, but I havent seen a simple tutorial yet so it seems like it will be annoying to figure out.

So EP, whats your suggestion for the cheapest way to get going, everything considered. Preferably something easy to program but Im looking for the cheapest way to get the chip and everything needed to program.

Picaxes seem nice but are a little hard to get a hold of. Atmega, never used them, and all the msp430's Ive ever used have been on dev boards. Any cheap arduino boards that meet my needs?

 

[(*steve*)]

What's your experience, what programmers do you have, what is your preference for language, is your application time critical, does your application require access to memory?

 

[dncky]

What's your experience, what programmers do you have, what is your preference for language, is your application time critical, does your application require access to memory?

Im going to make a stopwatch and hook it up to 2 digit seven segment display.

Experience is minimal, but I can figure stuff out given a decent tutorial. Have no programmers laying around. Language preference is C. Application is not time critical(not that much anyways).

Last one Im not sure how to field. Access to memory? Like what? I mean, Im going to stick some variables in there and I might write to some registers but nothing too involved

 

[(*steve*)]

Im going to make a stopwatch and hook it up to 2 digit seven segment display.

OK.

Experience is minimal, but I can figure stuff out given a decent tutorial. Have no programmers laying around. Language preference is C. Application is not time critical(not that much anyways).

PICaxe doesn't require a programmer, can't be used for *really* time critical stuff, But is programmed in BASIC (development environment is free)

Arduino can be a little more expensive (but there are cheaper options). It also doesn't require a programmer, but one can be handy. You can use it for time critical stuff. and is programmed in C (for which the development environment is free)

PIC is similar to Arduino, except you will require a programmer and it's perhaps a little less beginner friendly. Some free development environments are available, but there are paid-for versions too.

Last one Im not sure how to field. Access to memory? Like what? I mean, Im going to stick some variables in there and I might write to some registers but nothing too involved

Well, if you wanted to access a megabyte of memory, you would be looking off-chip. FOr a couple of kB you would need to choose an appropriate chip. For a handfull of bytes, almost anything will cope.

 

[dncky]

OK.



PICaxe doesn't require a programmer, can't be used for *really* time critical stuff, But is programmed in BASIC (development environment is free)

Arduino can be a little more expensive (but there are cheaper options). It also doesn't require a programmer, but one can be handy. You can use it for time critical stuff. and is programmed in C (for which the development environment is free)

PIC is similar to Arduino, except you will require a programmer and it's perhaps a little less beginner friendly. Some free development environments are available, but there are paid-for versions too.



Well, if you wanted to access a megabyte of memory, you would be looking off-chip. FOr a couple of kB you would need to choose an appropriate chip. For a handfull of bytes, almost anything will cope.

Comprehensive! Awesome

Picaxe might not require programmer, but Im still looking at buying that FTDI cable I believe it needs.

Arduino sounds good but Im very unfamiliar with them. Is there like an arduino dev board with USB programming and the 16 IO pins I need for like 10-15?

PICs are fine, but everything I seem to find seems to want a pickit of some other 40 50 dollar programmer

 

[(*steve*)]

Most of the "real" arduino boards are USB programmable.

I'd probably start by looking at the arduino nano. Also you'll find you can get similar devices a lot cheaper on eBay -- just make sure they are usb!

Unless you've really thought out your I/O usage, you may be able to get away with less I/O that you think right now (multiplexing, for example will allow you to drive both LED displays from 9 or 10 pins. It's also possible to reuse some of these pins for sensing inputs, but the arduino will have sufficient pins left for them anyway.

Note that the Nano has 14 digital I/O pins PLUS 8 analog input pins. These analog input pins can also be used for digital I/O, so you have 22 digital I/O pins at your disposal.

 

[dncky]

Most of the "real" arduino boards are USB programmable.

I'd probably start by looking at the arduino nano. Also you'll find you can get similar devices a lot cheaper on eBay -- just make sure they are usb!

Unless you've really thought out your I/O usage, you may be able to get away with less I/O that you think right now (multiplexing, for example will allow you to drive both LED displays from 9 or 10 pins. It's also possible to reuse some of these pins for sensing inputs, but the arduino will have sufficient pins left for them anyway.

Note that the Nano has 14 digital I/O pins PLUS 8 analog input pins. These analog input pins can also be used for digital I/O, so you have 22 digital I/O pins at your disposal.

Ah, this nano is promising. How reliable are these asian clones from ebay? Any experience? The price is definitely right

As for muxing the pins, I considered this, but thought of some problems. Say I mux all 14 pins for both seven segment displays. 4-16 mux. Ive got one of those.

But consider this, say I want to display, um, 24. Thats 9 segments that need to be on SIMULTANEOUSLY. The mux implementation will give me control of all 14 pins, but will only allow me to drive one at a time. Are you seeing something Im not?

ALLLLLSO, hows the environment setup for this, easy? What software will I need? Parts besides the usb cable required for programming the nano?

 

[(*steve*)]

Ah, this nano is promising. How reliable are these asian clones from ebay? Any experience? The price is definitely right

Well, I've not had any failures, but I am a small sample

Seriously, you might consider buying a brand name arduino first, and then move to the other clones later.

As for muxing the pins, I considered this, but thought of some problems. Say I mux all 14 pins for both seven segment displays. 4-16 mux. Ive got one of those.

But consider this, say I want to display, um, 24. Thats 9 segments that need to be on SIMULTANEOUSLY. The mux implementation will give me control of all 14 pins, but will only allow me to drive one at a time. Are you seeing something Im not?

No, that's what it does.

The normal way of multiplexing 7 segment digits is one digit at a time. So to display 20, you first display 2 on the first display (with the second blank) and then display 0 on the second display (with the first blank). You do it very fast so that you see 20 with no obvious flashing.

ALLLLLSO, hows the environment setup for this, easy? What software will I need? Parts besides the usb cable required for programming the nano?

For the development environment, go here. Simple!

I seem to recall getting a USB cable with each board I have purchased (notably excluding bare chips).

If you purchase a bare ATMega328 chip (for example) then you can use your arduino nano to make a programmer for it, or spend a couple of dollars getting a really cheap one.

 

[dncky]

Well, I've not had any failures, but I am a small sample

Seriously, you might consider buying a brand name arduino first, and then move to the other clones later.



No, that's what it does.

The normal way of multiplexing 7 segment digits is one digit at a time. So to display 20, you first display 2 on the first display (with the second blank) and then display 0 on the second display (with the first blank). You do it very fast so that you see 20 with no obvious flashing.



For the development environment, go here. Simple!

I seem to recall getting a USB cable with each board I have purchased (notably excluding bare chips).

If you purchase a bare ATMega328 chip (for example) then you can use your arduino nano to make a programmer for it, or spend a couple of dollars getting a really cheap one.

Ok. I might try one of these

http://www.ebay.com/itm/Arduino-Nan...990?pt=LH_DefaultDomain_0&hash=item417594335e

What do you think?

As for the LEDs, I've never driven them like that, but might do the trick. A cap might help, you recommend any size?

 

[(*steve*)]

Ok. I might try one of these

http://www.ebay.com/itm/Arduino-Nan...990?pt=LH_DefaultDomain_0&hash=item417594335e

What do you think?

I have purchased something almost identical.

The thing to note is that you need to ensure you solder the headers in straight if you're going to have any hope of plugging it into a breadboad.

I got a stack of matrix board underneath to hold the headers whilst I soldered them onto the board.

As for the LEDs, I've never driven them like that, but might do the trick.

If it's good enough for every other LED display, then I'm sure it's good enough for you.

A cap might help, you recommend any size?

No, a cap will definitely NOT help. It will cause ghosting which is exactly that you want to avoid.

If you have enough outputs, there is nothing stopping you from driving them all directly. But consider what you would do if you wanted a 6 digit or an 8 digit, or an 18 digit display.

 

[dncky]

Will buy the nano board. Reply with results