Yup. Definitely looks like the cheapest way is to drive the segments of the common anode display directly to ground right from a uC, if it can take the punishment.
If there were more displays to drive instead of instead of just one, it might be worth looking at using a dedicated driver chip for each display. Or who knows, it might still be cheaper to use a uC for each display, slaved together on a serial bus.
MCUs often have a total sink rating which can limit how many loads you drive at the same time.
Not sure what you've found before, but a quick search turned up some TI parts, TLC6C598 - 8 bits, $0.34 and TLC6C5912 - 12 bits, $0.50 at 1k quantity. These are basic shift registers with a clear and buffer register (open drain output) with a blanking control which can be used for PWM. 30 mA per output up to 40 volts. Supply current in uA.
-- Rick C
I had to update a product that used two of them recently. What I opted to use was an AS1109. It uses an SPI style interface instead of a parallel BCD input and you will need to use a look up table for the decoding, but that's all pretty trivial. It has a single input for dimming and you can daisy chain them together so you don't need multiple /CS lines. It also has the advantage of a built in CC driver, so you don't need to put down individual resistors for each output and a dimming input that handles all the output channels. Don't know if that will work for you, but it's worth a look.
The TLC6C598 is a cool part...if at some point I have to control more than one display it would make sense to use that for each and drive them from a single uC,
I was surprised though that most AVR uCs in SOIC can sink a total of 200 mA to ground, at usually 20 mA or over per pin. The packages have a total dissipation rating of 500 mW at 30C, so if the output low voltages are only a few hundred mV I think I should come in under that, even with 7 segments.
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