Peeking at Espruino Board Timers 2, 3, 4, and 5

Properties of Timers 2, 3, 4, and 5
Valid pins for PWM analogWrite:

analogWrite(A4,0.1,{ freq : 10 });

ERROR: Pin A4 is not capable of PWM Output
Suitable pins are:
A0 A1 A2 A3 A6 A7(AF) A8 A9 A10
A11 B0(AF) B1(AF) B3(AF) B4(AF) B5(AF) B6 B7 B8
B9 B10(AF) B11(AF) B13 B14 B15 C6(AF) C7(AF) C8(AF)
C9(AF)
Or pins with DAC output are:
A4 A5
You can also use analogWrite(pin, val, {soft:true}) for Software PWM on this pin
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Note the AF notation AF = Alternate Function
Using the attached file isTimerEnabled1.js and modifying the analog Write statements
Timer 5 uses pins:
A0, A1, A2, A3 or AF pins
Timer 4 uses pins:
B6, B7, B8, B9 or AF pins
Timer 3 uses pins:
A6, A8, A9, A10 or AF pins B4, B5, B0
Timer 2 uses pins:
Or AF pins B3, B10, B11.
Pins B1, A7, B13, B14, B15, C6, C7, C8, C9 are not seen by timers 2, 3, 4, or 5 when
used in a PWM analog Write statement.
When isTimerEnabled1.js is used with the following analogWrite commands,

analogWrite(A0,0.1,{ freq : 10 }); 
analogWrite(A1,0.2,{ freq : 10 }); 
analogWrite(A2,0.3,{ freq : 10 }); 
analogWrite(A3,0.4,{ freq : 10 });
The output:
>echo(0);
Timer 2 Disabled
Timer 3 Disabled
Timer 4 Disabled
Timer 5 Enabled
CR1=81
CR2=0
SMCR=0
DIER=0
SR=1
ERRCW=0
CCMR1=6868
CCMR2=6868
CCER=1111
CNT=1da5
PSC=6d
ARR=ffae
CCR1=1991
CCR2=3322
CCR3=4cb4
CCR4=6645
DCR=0
DMAR=81

Note the CCR1 thru CCR4 reflect the different duty cycles specified in the analogWrite commands.
If the analog Write commands are changed to

analogWrite(A6,0.1,{ freq : 10 }); 
analogWrite(A8,0.2,{ freq : 10 }); 
analogWrite(A9,0.3,{ freq : 10 }); 
analogWrite(A10,0.4,{ freq : 10 });
The Output:
>echo(0);
Timer 2 Disabled
Timer 3 Enabled
CR1=81
CR2=0
SMCR=0
DIER=0
SR=1
ERRCW=0
CCMR1=68
CCMR2=0
CCER=1
CNT=16e2
PSC=6d
ARR=ffae
CCR1=1991
CCR2=0
CCR3=0
CCR4=0
DCR=0
DMAR=81
Timer 4 Disabled
Timer 5 Disabled

Note that CCR1 is non zero but CCR2, CCR3, and CCR4 are zero.

The program PWMflash.js looks for pulses divides them and flashes the red LED.
I used this to test the PWM properties.

var FLED=require("flashLED");

var x=new FLED(5);

analogWrite(A0,0.1,{ freq : 10 }); 
analogWrite(A1,0.1,{ freq : 1 }); 
setWatch(x.divide, C3,
{ repeat: true, edge:'rising', debounce:1});

/*
function FLED(a) {
  this.A=a;
  this.count=0;
  this.LEDstate=0;
}

exports = FLED;
FLED.prototype.divide = function() {
 this.count++;
 if(this.count<this.A)return;
 this.count=0;
 this.LEDstate=this.LEDstate^1;
 digitalWrite(LED1,this.LEDstate);
};//divide

exports=FLED;

*/

While the duty cycles of pins A0, A1, A2, and A3 can be independently altered, they must all use the same frequency. The frequency is that of the last invoked analogWrite PWM command.

2 Attachments

• PWMflash.js
• isTimerEnabled1.js