View Single Post
Old 07-27-2011   #48
jarmster
Member
 
jarmster's Avatar
 
Join Date: Feb 2011
Posts: 380
Likes: 50
Liked 86 Times in 58 Posts
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Originally Posted by baball View Post
Read judge post. Don't need regulator...
I know that...where do i say use it?

Actually, heres pics of the power mod, except you dont need to add the regulator

Originally Posted by judges View Post
And yes, according to the Teensy specs, it should only run at 8 MHz on 3.3V. I'll also update this.
The AVR processor is not specified to run faster than 8 MHz when running at 3.3 volts, even though it often can operate at 16 MHz at room temperature.
You do NOT need to replace the 16 MHz crystal. Just set the CPU prescaler to 0x01 so the processor runs at 8 MHz.

#define CPU_PRESCALE(n) (CLKPR = 0x80, CLKPR = (n))

int main(void)
{
// set for 8 MHz clock because 3.3 volts
CPU_PRESCALE(0x01);

// rest of program....]
You also need to edit your Makefile to change F_CPU to 8000000.
# Processor frequency.
# Normally the first thing your program should do is set the clock prescaler,
# so your program will run at the correct speed. You should also set this
# variable to same clock speed. The _delay_ms() macro uses this, and many
# examples use this variable to calculate timings. Do not add a "UL" here.
F_CPU = 8000000
Looking at the schematic, don't you tie the 3.3v nor vcc to the teensy 5v. Your hardware connections doesn't show the 3.3 volt tie to the teensy

Last edited by jarmster; 03-17-2012 at 10:59 AM.
jarmster is offline   Reply With Quote