Re: Need help with microprocessor control, selecti
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billw said:
The AVR tiny series is a pretty good compromise in price, performance, and availability. The ATtiny11 can be obtained for $0.25 to $0.50 each, which is phenomenal (but it's a relatively icky chip.)
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I agree about the ickiness of the ATTiny11. But consider instead the
ATTiny15L, which is pretty good for power supplies and LED lighting, for two big reasons:
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[*]The 10-bit A/D converter, including a 20x differential input that's great for current sensing. The PIC 10F chips don't have A/D (yet); the PIC 12F675 does. But the PICs don't have the 20x differential amplifier.
[*]The high-speed PWM, which lets you have a 8-bit, 100KHz output that means smaller inductors. The best the PICs can do (especially the small ones) is 32KHz PWM.[/list]
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Some ATtiny's are programmable in a free C compiler (gcc) (however, gcc only works on AVRs that have separate ram, which does NOT include many of the ATtiny parts.)
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Actually,
most (4/7 parts) of the ATTiny chips now have RAM. Especially the other great contender for power supplies, the
ATTiny26L. This chip has
two high-speed PWM (250KHz max) channels with complementary outputs, and 11 A/D channels, in a 20-pin SOIC or DIP package, or a 5mm square MLF-32 package. You can have your choice of multiple single-ended,
1x, or 20x differential channels on the 10-bit A/D.
The
ATTiny13V has RAM, 4 A/D channels, and 2 PWM channels (max 39 KHz from 2.7 to 5.5V) in an 8-pin package. And it works from 1.8V to 5.5V.
As for the ATTiny15L, which doesn't have a separate RAM stack but does have 32 general-purpose registers:
you can program the ATTiny15L with GCC if you're careful. Just don't tell the compiler it's RAMless (just use the default processor family), don't use the avr-libc headers (I've made my own headers for the Tiny15L that generate efficient code from readable C), and check the assembly output afterwards. Always use the optimizer. I've been using GCC for the Tiny15L and am quite happy with its code generation. Of course, with only 512 words of program memory, you could use assembly language just as well, but if you change chip families a lot (I go back and forth between the AVR and PIC 18F chips), C is great for most projects.
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The main competitor is the the PIC 12F series (also 8 pins) and new 10F series (6 pin SOT23-style package!) Prices and capabilities are "similar"; the rivalry is at times intense.
Other small micros include the Fairchild ACE and some cygnal (now
silabs) 8051 variants.
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And of course the other big contender in the 8-bit 8-pin micro space is Freescale (the chip company formerly known as Motorola Semiconductor). Their 68HC908 series is super easy to program (they have a built-in monitor program), and they also have a free C compiler that's fine for the smaller chips (up to 4K of code). Nice timer units, but only 8-bit A/D converters. No really high speed PWM.
Bruce Lightner's description of how to use AVR-GCC on the Tiny15L
My page on the same thing
