Colin Snow
The ATtiny is a microcontroller that can be put into sleep mode to conserve power. This is particularly useful for battery-operated devices, where the goal is to have the device run for as long as possible without needing to replace or recharge the batteries. To enable sleep mode, the ATtiny's pins must be set to 'interrupt-on-change', allowing the chip to 'wake-on-interrupt'. This can be achieved through the use of code, with the specific method depending on the programming language and hardware being used.
ATtiny Sleep Mode Characteristics
| Characteristics | Values |
|---|---|
| Consumption in sleep mode | 69μA (including 20μA from brown-out detector) |
| Consumption in sleep mode without brown-out detector | 1μA |
| Consumption when LED is OFF without sleep mode | 4mA |
| Active clock domains in idle mode | Clock to IO, ADC, and PLL oscillator |
| Active clock domains in ADC noise reduction mode | ADC clock |
| Clock domains in power-down mode | All clock sources halted |
| Power consumption in power-down mode | Lowest out of all sleep modes |
| Wake-up sources in power-down mode | INT0 and Pin change interrupts, USI (serial communication) start condition, and Watchdog interrupts |
| Sleep mode command | set_sleep_mode(SLEEP_MODE_PWR_DOWN) |
| Sleep enable command | sleep_enable() |
| Sleep command | sleep_cpu() or asm volatile ("sleep"\n\t" ::) |
| Wake-up source | Interrupt, ADC, USI, etc. |
| Sleep mode selection | Bits SM1 and SM0 from MCUCR register |
| Sleep enable bit | SE in MCUCR register |
| Interrupt configuration | PCMSK = (1 << PCINT0); GIMSK = (1 << PCIE); sei(); |
| Interrupt service routine | ISR (PCINT0_vect) |
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What You'll Learn
Using the SLEEP command
The SLEEP command is used to put an Attiny microcontroller to sleep, which can be useful for conserving battery power. To use the SLEEP command, you need to follow these steps:
First, set the sleep mode by using the set_sleep_mode() function and specifying the desired sleep mode, such as SLEEP_MODE_PWR_DOWN for power-down mode. This will halt all clock sources and result in the lowest power consumption.
Next, enable sleep by using the sleep_enable() function. This will set the Sleep Enable (SE) bit in the MCU Control Register (MCUCR).
Then, you can issue the SLEEP command to put the microcontroller into the sleep state. This can be done by using the sleep_cpu() function or by calling the "sleep" instruction directly.
It is important to note that before putting the microcontroller to sleep, you should configure the wakeup sources such as interrupts, ADC, USI, etc. This will ensure that the microcontroller can be woken up from the sleep state when needed. The specific wakeup sources will depend on the sleep mode being used. For example, in power-down mode, the controller can be woken up using INT0 and Pin change interrupts, USI serial communication start condition, or Watchdog interrupts.
Additionally, you can use the sleep.h header file, which is part of avr-libc, to simplify the process of issuing the SLEEP command. This will not incur any overhead compared to implementing it manually.
By following these steps, you can effectively use the SLEEP command to conserve power in Attiny microcontrollers.
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Deep sleep for ATtiny45
Deep sleep is a crucial feature for low-power applications, enabling ATtiny microcontrollers to operate for extended periods on battery power. The ATtiny45, a member of the ATtiny family, can be configured for deep sleep to achieve ultra-low power consumption, making it ideal for battery-operated devices.
To put an ATtiny45 into deep sleep, you can utilise the TinySnore library, a popular and convenient option. This library simplifies the process, allowing you to initiate deep sleep with a single line of code: "snore(ms)", where "ms" represents the desired sleep duration in milliseconds. The TinySnore library offers flexibility, accommodating sleep durations ranging from 16ms to 4,294,967,295ms (approximately 49 days).
Here's an example code snippet demonstrating how to use the TinySnore library to put an ATtiny45 into deep sleep for one second:
C++
#include "tinysnore.h"
#define LED 4
Void setup() {
PinMode(LED, OUTPUT);
}
DigitalWrite(LED, HIGH);
Delay(1000);
DigitalWrite(LED, LOW);
Snore(1000); // Deep sleep for 1 second
}
In this code, the LED is turned on using `digitalWrite(LED, HIGH)`, followed by a 1-second delay. Then, the LED is turned off with `digitalWrite(LED, LOW)`, and the ATtiny45 is put into deep sleep for 1 second using `snore(1000)`.
It's important to note that the sleep duration in TinySnore is not always precise down to the millisecond, especially for longer sleep periods. To achieve greater precision, you can use `millis()` to compensate for drift, checking it in each loop iteration or at regular intervals.
The ATtiny45's deep sleep capability is impressive, drawing less than 0.2µA when running off a 3V coin cell at room temperature. This efficiency enables the microcontroller to remain in a deep sleep state, awaiting a button press for over 100 years, surpassing the typical battery lifespan.
While deep sleep is a valuable power-saving feature, it's important to consider the trade-offs. During deep sleep, the ATtiny45 may not be able to detect external events or respond to interrupts. Therefore, careful consideration is required when designing applications that need to balance power consumption and responsiveness.
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Using interrupts
To use interrupts to wake up an ATtiny from sleep, you can use the following methods:
Using Pin Change Interrupts
Firstly, you need to set the pins to 'interrupt-on-change' and configure the interrupt. This can be done by setting the appropriate bits in the Pin Change Mask (PCMSK) and General Interrupt Mask (GIMSK) registers. For example, to use pin PB0 as an interrupt pin, you would set PCINT0 in the PCMSK register and enable pin change interrupts in the GIMSK register.
Using Timer Interrupts
Another method is to use timer interrupts, such as the Timer 0 overflow interrupt, to wake up the ATtiny from sleep. This can be useful for specific timing requirements, such as waking up every five minutes to write data to EEPROM.
Using External Interrupts
External interrupts can also be used to wake up the ATtiny from sleep. This involves configuring an external interrupt pin and enabling the interrupt in the Interrupt Service Routine (ISR).
C
#include
#include
Int ledPin = 0;
Int interruptPin = 4;
Int wakePin = 2;
Void setup(){
PinMode(ledPin, OUTPUT);
PinMode(interruptPin, OUTPUT);
PinMode(wakePin, INPUT);
DigitalWrite(wakePin, HIGH);
}
Void sleepNow(){
Set_sleep_mode(SLEEP_MODE_PWR_DOWN);
Sleep_enable();
AttachInterrupt(0, wakeUpNow, LOW);
DigitalWrite(ledPin, LOW);
}
Void wakeUpNow(){
DigitalWrite(interruptPin, HIGH);
}
Void loop(){
Sleep();
DigitalWrite(statusLED, HIGH);
Delay(1000);
DigitalWrite(statusLED, LOW);
}
In this code, the `sleepNow()` function sets the sleep mode, enables sleep, attaches an interrupt to pin 2, and turns off the LED. The `wakeUpNow()` function is executed when the interrupt is triggered, turning on the interrupt LED. The `loop()` function calls the `sleep()` function, which puts the ATtiny to sleep and handles the interrupt when it wakes up.
By using these interrupt methods, you can effectively manage the sleep and wake-up behaviour of an ATtiny, allowing it to conserve power and respond to external events.
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Power consumption in sleep mode
The ATtiny microcontroller is a low-power device that can be put into a sleep mode to reduce power consumption. Sleep mode can be enabled by setting the sleep mode sleep enable (SE bit) and issuing a SLEEP command. This can be done using the <'sleep.h' library> or by setting the SM [1:0] and SE bits directly.
The power consumption of the ATtiny in sleep mode depends on various factors, including the specific model of the ATtiny, the voltage supplied to it, and the configuration of its pins. For example, the ATtiny85 is specified to consume 0.1 µA at 1.8V in power-down mode according to its datasheet. However, one user reported a higher current consumption of 300 µA in power-down mode when powering the ATtiny85 with two AAA batteries in series, which provide around 3V.
Additionally, the current consumption in sleep mode can be affected by the configuration of the input and output pins. For instance, unconnected floating input pins can cause excessive current draw as the voltage on these pins can be anywhere between GND and VCC, partially turning on both the P-MOS and N-MOS transistors and creating a small amount of current. To mitigate this, unused pins should be set as outputs and given a defined value of either 1 or 0 to prevent them from floating.
Furthermore, it is important to disable all unnecessary modules and oscillators to minimize power consumption in sleep mode. For example, enabling the watchdog timer or the RC oscillator can increase the current draw. By carefully configuring the ATtiny and its pins, users can achieve lower power consumption and extend the battery life of their devices.
Overall, the ATtiny's sleep mode can significantly reduce power consumption, but careful configuration and testing are required to optimize power savings and ensure the device functions as intended.
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ATtiny85 sleep modes
Sleep mode is a valuable feature in microcontrollers, especially with the growing demand for portable embedded devices. Power management is an absolute necessity, and microcontrollers are equipped with sleep mode functionality to address this. The ATtiny85 microcontroller has three types of sleep modes, each allowing for a different level of power-saving functionality by letting users disable different sets of peripherals in the controller.
In idle mode, the clock to IO, ADC, and PLL oscillator will be active. In ADC noise reduction mode, only the ADC clock will be active. In power-down mode, all clock sources will be halted, resulting in the lowest power consumption among the sleep modes.
To put the ATtiny85 into sleep mode, you must first set the sleep mode sleep enable (set the SE bit) and issue the SLEEP command. This can be done with the aid of the 'sleep.h' library, which is a header file that is part of avr-libc. The relevant parts will be inlined by the compiler, and any unused parts of the header file will not be included in the compiled result. The following code can be used:
Set_sleep_mode(SLEEP_MODE_PWR_DOWN);
Sleep_enable();
Sleep_cpu();
If you do not want to use the 'sleep.h' library, you can set the sleep mode and sleep enable via 3 bits (SM [1:0] and SE). However, you will still need to issue the SLEEP command.
It is important to configure the wakeup sources (such as interrupts, ADC, and USI) before putting the controller into a sleep state. Failing to do so will result in the controller entering sleep mode without any way to wake it up. To wake the controller from sleep, you can use the configured wakeup source.
Additionally, putting the output pins into input before sleep mode can save a significant amount of current. This can be an effective way to reduce power consumption and increase the battery life of devices using the ATtiny85 microcontroller.
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Frequently asked questions
To use sleep in ATtiny, you need to set the sleep mode, enable sleep, and then issue the SLEEP command. This can be done using the 'sleep.h' library or by setting the sleep mode and sleep enable via 3 bits (SM [1:0] and SE).
The different sleep modes in ATtiny include idle mode, ADC noise reduction mode, and power-down mode. In idle mode, the clock to IO, ADC, and PLL oscillator will be active, while in ADC noise reduction mode, only the ADC clock will be active. Power-down mode halts all clock sources, resulting in the lowest power consumption.
The ATtiny can be woken up from sleep by various sources, including interrupts, ADC, USI, and watch dog interrupts. It is important to configure the wakeup sources before putting the controller to sleep, as failing to do so may result in the controller entering sleep mode without any way to wake it up.
The power consumption of ATtiny in sleep mode depends on various factors, such as the enabled modules and the sleep mode used. In power-down mode, the power consumption is typically the lowest. For example, one user reported a consumption of 69μA in sleep mode, including 20μA from the brown-out detector.
Yes, it is possible to use a button to enable and disable sleep mode in ATtiny. This can be achieved by configuring the interrupt service routine (ISR) and setting the pins to 'interrupt-on-change' and 'wake-on-interrupt'. When the button is pressed, the interrupt is triggered, and the ATtiny can wake up from sleep mode.
