Mike Chambers
Well-known member
I'm trying to find ways to save power on my T4.1 NES mini arcade. It's a heavy project to run on 3x AA batteries in series, and they will need to be replaced often or I need to use rechargables if I can't find some way to cut power usage significantly. There's a T4.1, TFT LCD, and an LM386 audio amp IC. One thing that should help is putting a resistor on the backlight power pin. Save power at the expense of some brightness.
I've found the slowest I can run the CPU and still get full speed emulation is the 528 MHz setting. The only features of the Teensy that I'm actually using are GPIO, timers, SD card and PWM (combined with low-pass filter for audio). Can a significant amount of power be saved by disabling everything else?
One thing I experimented with was running the CPU faster and then setting the clock to 24 MHz when it's just waiting for timing between scanlines, but that caused all sorts of issues. Inconsistent performance, audio timing problems, etc. I'm not sure if that would have really saved power anyway versus just running the CPU at the minimum constant clock to achieve full speed. How about running the CPU faster and just using a sleep mode between scan lines?
I originally tried to do this without an LM386, but as expected, after limiting the PWM pin's output current to a value that won't damage it, it's just too quiet to do the job adequately.
Is there anything else I'm not thinking about? All of my past projects have been things that had a constant power source, no batteries. So, power consumption has never really been something I've had to give deep thought to before.
Once I added the ability to monitor on-screen the voltage level of the batteries, I could see that they drain FAST! I bet I could get maybe an hour out of them before they're spent. Maybe I'm asking too much from 3x AA, but getting 2+ hours would be nice. It's not like someone would play through a full game on this very often. It's more of a cool little decoration/novelty that's also playable if desired!
I've found the slowest I can run the CPU and still get full speed emulation is the 528 MHz setting. The only features of the Teensy that I'm actually using are GPIO, timers, SD card and PWM (combined with low-pass filter for audio). Can a significant amount of power be saved by disabling everything else?
One thing I experimented with was running the CPU faster and then setting the clock to 24 MHz when it's just waiting for timing between scanlines, but that caused all sorts of issues. Inconsistent performance, audio timing problems, etc. I'm not sure if that would have really saved power anyway versus just running the CPU at the minimum constant clock to achieve full speed. How about running the CPU faster and just using a sleep mode between scan lines?
I originally tried to do this without an LM386, but as expected, after limiting the PWM pin's output current to a value that won't damage it, it's just too quiet to do the job adequately.
Is there anything else I'm not thinking about? All of my past projects have been things that had a constant power source, no batteries. So, power consumption has never really been something I've had to give deep thought to before.
Once I added the ability to monitor on-screen the voltage level of the batteries, I could see that they drain FAST! I bet I could get maybe an hour out of them before they're spent. Maybe I'm asking too much from 3x AA, but getting 2+ hours would be nice. It's not like someone would play through a full game on this very often. It's more of a cool little decoration/novelty that's also playable if desired!
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