I'm trying to figure out the best way to drive a 4-Digit, 7-Segment display and have found the MAX7219 chip to be very popular, but it is somewhat expensive and I'm wondering if there is something that would be smaller and cheaper, but able to run 4 digits of a 7-Segment display, instead of the full 8. Is there anything out there that would do that?
Another possibility, however, would be something that could drive the 4 digits plus 3 RGB LEDs with PWM. I know the MAX7219 has enough channels to drive all those LEDs, but it would be without PWM, which I absolutely need to have for the RGBs. I'm already planning on using a TLC5940 for those, but having a single chip solution would be great.
You might take a look at the STLED316S - fairly cheap but surface mount only. It's a "front panel controller" so it can handle switches as well as drive LEDs (common anode).
That was the dillema I was posed with, when figuring out how to drive my 8x8(x2 color) led matrix I bought from sparkfun, however for my alternative, I am just using the Atmega32L with the arduino bootloader. That way I have all the lights covered with one chip that ends up being cheaper than one MAX7219 chip. Go buy a pack of transistors, and your golden
Here's a proof of concept sketch I drew up in Fritzing.
I also have video and images of the POC as well since this is going to be a bigger project than just the matrix itself, and there are multiple concepts that are going into this system I am making.
What is wrong with driving continuously? You just write to the shift register once and the data stays there.
You can also set up the shift registers to be independently loadable (common data, common shift clock, separate load clock, 6 pins total vs 3 with SPI) and just update 1 digit at a time like you would do with the 7219/7221.
I've only asked for a couple at a time in case I smoked the first part. Free shipping. May take days for delivery if coming from the Phillipines or someplace like that.
Am waiting on some SPI driven USARTs right now to see about adding 2nd HW serial port at 230K transmit speeds.
Ordered a crystal from dipmicro to go with it. They are very inexpensive too, 5-25 cents for many parts, $2.xx for standard shipping.
Yeah, that's why I wish there was some kind of local supply electronics supply house around here, because shipping is usually more than 1/2 the order on what I usually want to buy :\
Wish I could do reflow and smd soldering.. I have a board out of a lexmark printer that has a mighty fine stepper motor controller, some kinda motorolla micro (useless though, proprietary and no schematic), serial addressable 512k chips, and a few other notable pieces. All I have is a cheap soldering iron I got for christmas two years ago. I have burnt the tip to hell and back (recently shaved and works pretty good still) but definitely not a fine tip.
Maxim ships MAX72xx from California, I got some in the mail yesterday and I only requested them last week. There were sent via FedEx at no charge to me.