com.sun.spot.peripheral
Interface IAT91_TC

All Superinterfaces:

IDriver

public interface IAT91_TC
extends IDriver

Interface to an AT91 Timer Counter.

The AT91 Timer Counter includes three identical 16-bit Timer Counter channels.

Each channel can be independently programmed to perform a wide range of functions including frequency measurement, event counting, interval measurement, pulse generation, delay timing and pulse width modulation.

Each channel has three external clock inputs, five internal clock inputs and two multi-purpose input/output signals which can be configured by the user. Each channel drives an internal interrupt signal which can be programmed to generate processor interrupts.

For a full description of the AT91 Timer Counter please refer to the Atmel documentation. Here we will provide a few basics to allow using the Timer to generate a periodic interrupt. For Timer Counter bit definitions please see TimerCounterBits.

Several signals are provided on the SPOT processor board via the top connector, though the initial eDemo sensor board does not make them available. The available signals are the three external clock inputs (TCLK0, TCLK1, TCLK2) and the general purpose input/output pins for channel 0 (TIOA0, TIOB0).

The Timer Counter can operate in two distinct modes: Capture & Waveform generation. In either mode the rate at which the Timer counts is determined by which internal clock is used. The available clock speeds are:

• 29,952 Khz: One count = 0.0334 usec. Max duration = 2.188 msec. (TimerCounterBits.TC_CLKS_MCK2)
• 7,488 Khz: One count = 0.1335 usec. Max duration = 8.752 msec. (TimerCounterBits.TC_CLKS_MCK8)
• 1,872 Khz: One count = 0.5342 usec. Max duration = 35.009 msec. (TimerCounterBits.TC_CLKS_MCK32)
• 468 Khz: One count = 2.1368 usec. Max duration = 140.034 msec. (TimerCounterBits.TC_CLKS_MCK128)
• 32.768 Khz: One count = 30.5176 usec. Max duration = 2,000 msec = 2 sec. (TimerCounterBits.TC_CLKS_SLCK)

To use the Timer to measure an interval use Capture Mode, enable the clock to start it counting, and at the end of the interval just read the counter value:

    IAT91_TC timer = Spot.getInstance().getAT91_TC(0);
    timer.configure(TC_CAPT | TC_CLKS_MCK32);
    timer.enableAndReset(); 
    ... interval to measure ...
    int cntr = timer.counter();
    double interval = cntr * 0.5342;  // time in microseconds
 

To generate periodic interrupts modify the above code to set the RC Register to the number of counts that will span the desired period, and enable interrupts on RC Compare:

    IAT91_TC timer = Spot.getInstance().getAT91_TC(0);
    int cnt = (int)(25000 / 0.5342);  // number of clock counts for 25 milliseconds
    timer.configure(TC_CAPT | TC_CPCTRG | TC_CLKS_MCK32);
    timer.setRegC(cnt);
    timer.enableAndReset();
    while(true) {
        timer.enableIrq(TC_CPCS);     // Enable RC Compare interrupt
        timer.waitForIrq();
        timer.status();               // Clear interrupt pending flag
        doTask();                     // method will be called every 25 milliseconds
    }
 

A Java thread detects an interrupt by calling waitForIrq(). This method performs a Channel IO request. If the Timer Counter interrupt bit is set the request returns immediately. If not the calling thread is blocked until the interrupt occurs. To clear the interrupt bit call status().

To handle an interrupt in Java you must:

1. Call configure(int) to configure the timer so that it will generate an interrupt request.
2. Call enableAndReset() to start the timer counting
3. Call enableIrq(int) to enable one or more of the interrupt sources associated with this TC channel.
4. Call waitForIrq() to wait for the interrupt.
5. Call status() to clear the interrupt.
6. Call enableIrq(int) to allow another interrupt.
7. Repeat from 4)

If you don't want more interrupts then don't call enableIrq(int).

Author:

Syntropy

See Also:

AT91 Spec

Method Summary

void	blockSync() Perform a block sync command, which causes a reset of all three counters
void	claimTCLK() Enable PIO use of shared TCLK line
void	claimTIOA() Disable PIO use of shared TIOA line
void	claimTIOB() Disable PIO use of shared TIOB line
void	configure(int mask) Configure the Timer-Counter
void	configureXC(int xcMask) Configure the block mode inputs appropriate to this TC channel
int	counter() Read current counter value
void	disable() Disable the counter
void	disableIrq(int mask) Disable one or more of the interrupt sources associated with this TC channel.
void	enable() Enable counter
void	enableAndReset() Enable counter and cause software trigger which forces a reset on next clock edge
void	enableIrq(int mask) Enable one or more of the interrupt sources associated with this TC channel.
int	regA() Read current Reg A value
int	regB() Read current Reg B value
void	setRegA(int i) Set the value of the A Compare Register
void	setRegC(int i) Set the value of the C Compare Register
int	status() Read current status
void	unclaimTIOA() Enable PIO use of shared TIOA line
void	waitForIrq() Suspend this thread until this TC generates an interrupt.

Methods inherited from interface com.sun.spot.peripheral.IDriver

getDriverName, setUp, shutDown, tearDown

Method Detail

configure

void configure(int mask)

Configure the Timer-Counter

Parameters:

mask - bits to set in TC_CMR

enableAndReset

void enableAndReset()

Enable counter and cause software trigger which forces a reset on next clock edge

enable

void enable()

Enable counter

counter

int counter()

Read current counter value

Returns:

TC_CV

status

int status()

Read current status

Returns:

TC_SR

claimTIOA

void claimTIOA()

Disable PIO use of shared TIOA line

unclaimTIOA

void unclaimTIOA()

Enable PIO use of shared TIOA line

claimTIOB

void claimTIOB()

Disable PIO use of shared TIOB line

claimTCLK

void claimTCLK()

Enable PIO use of shared TCLK line

regA

int regA()

Read current Reg A value

Returns:

TC_RA

regB

int regB()

Read current Reg B value

Returns:

TC_RB

setRegC

void setRegC(int i)

Set the value of the C Compare Register

Parameters:

i - Value to be set

setRegA

void setRegA(int i)

Set the value of the A Compare Register

Parameters:

i - Value to be set

disable

void disable()

Disable the counter

configureXC

void configureXC(int xcMask)

Configure the block mode inputs appropriate to this TC channel

Parameters:

xcMask - Bits to be set in TC_BMR

blockSync

void blockSync()

Perform a block sync command, which causes a reset of all three counters

enableIrq

void enableIrq(int mask)

Enable one or more of the interrupt sources associated with this TC channel.

Parameters:

mask - Bit mask identifying the required interrupt source(s)

waitForIrq

void waitForIrq()

Suspend this thread until this TC generates an interrupt. You must call enableIrq(int) prior to this, and again if you want a subsequent interrupt.

disableIrq

void disableIrq(int mask)

Disable one or more of the interrupt sources associated with this TC channel.

Parameters:

mask - Bit mask identifying the required interrupt source(s)