Eric Hertz@Mark Sherman has shared a wealth of great ideas... go check out his projects.
He just pointed out something I hadn't considered...
Many AVRs have an 8bit multiply instruction which executes in 2 clock-cycles.
These same AVRs usually only have a *single* shift-instruction, so to shift-left 3 times actually takes *more* clock-cycles than to use a multiply-by-8!
"The more you know!"
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I also just realized that multiply can be used to shift right multiple places.
Suppose you have the binary value 11001101 in a register. You want to shift left 5 places.
You multiple by 2^5:
1100110100000
The avr stores the 16-bit result across 2 registers
0011001 10100000
The low register has the value shifted left 5 places
The high register ahs the value shifted right 3 places!
To shift left N places: multiply by 2^N, take low byte of result
To shift right N places: multiply by 2^(8-N), take high byte of result.
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Mind Blown. I'mma have to look into that! Didn't realize the multiply instruction fed into a 16-bit register, and that trick is pretty durn clever.
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