Hi,
I'm experimenting with Teensy on low power, and found something that I can't explain.
Currently Teensy runs on 3.3V and 4MHz.
When I power it up, consumed current is 12.4mA.
It's very different from my expectations, because it should consume 10.6mA on 3.3V/8MHz, so on 4MHz it definitely should be less than 10.6mA.
When I connecting USB, and consumed current drops down to 7.5mA.
Wow.
I expected that USB will eat some additional power from battery.
And when I'm disconnecting USB, consumed current drops down again to 4.2mA.
Hmmmm....
And now when I'm connecting/disconnecting USB, consumed current is 7.5/4.2mA.
I tried to power it up with connected USB, and then I see 7.5/4.2mA from the beginning and there is no 12.4mA peak.
I'm using TMK firmware for my experiments (
https://github.com/tmk/tmk_keyboard/tree/master/keyboard/onekey) because I'm familiar with it, and after all I want to make BT keyboard
Everything I've changed - it's just set cpu prescaler during matrix initialization:
--- ../onekey/matrix.c 2015-01-03 13:38:59.383088670 +0200
+++ ./matrix.c 2015-03-06 04:07:57.022047139 +0200
@@ -21,6 +21,7 @@
#include <stdint.h>
#include <stdbool.h>
#include <avr/io.h>
+#include <avr/interrupt.h>
#include <util/delay.h>
#include "print.h"
#include "debug.h"
@@ -57,6 +58,12 @@
void matrix_init(void)
{
+ // set CPU speed
+ cli();
+ CPU_PRESCALE(CPU_4MHz);
+ sei();
+
debug_enable = true;
debug_matrix = true;
debug_mouse = true;
Obviously, TMK firmware does not doing something on start, what it doing when USB is connected.
This "something" is very influencing to power consumption.
Unfortunatly, I have no clue what this could be.
Any help, ideas and directions to experimenting really much appreciated.
I need full power of your telepathy
