In general, the extended reset cause supercedes the raw code. The raw code is kept for backwards compatibility only. For new applications it is highly recommended to use the extended reset cause instead.
In case of extended reset cause 3 (exception reset), additional values are returned containing the crash information. These are, in order, EXCCAUSE, EPC1, EPC2, EPC3, EXCVADDR, and DEPC.
Enters deep sleep mode. When the processor wakes back up depends on the supplied `options`. Unlike light sleep, waking from deep sleep restarts the processor, therefore this API never returns. Wake up can be triggered by a time period, or when a GPIO (or GPIOs) change level, or when a touchpad event occurs. If multiple different wakeup sources are specified, the processor will wake when any of them occur. Use [`node.bootreason()`](#nodebootreason) to determine what caused the wakeup.
Only RTC GPIO pins can be used to trigger wake from deep sleep, and they should be configured as inputs prior to calling this API. On the ESP32, the RTC pins are GPIOs 0, 2, 4, 12-15, 25-27, and 32-39. An error will be raised if any of the specified pins are not RTC-capable. If multiple pins are specified and `level=1` (which is the default), the wakeup will occur if *any* of the pins are high. If `level=0` then the wakeup will only occur if *all* the specified pins are low.
-`secs`, a number of seconds to sleep. This permits longer sleep periods compared to using the `us` parameter.
-`us`, a number of microseconds to sleep. If both `secs` and `us` are provided, the values are combined.
-`gpio`, a single GPIO number or a list of GPIOs. These pins must all be RTC-capable otherwise an error is raised.
-`level`. Whether to trigger when *any* of the GPIOs are high (`level=1`, which is the default if not specified), or when *all* the GPIOs are low (`level=0`).
-`isolate`. A list of GPIOs to isolate. Isolating a GPIO disables input, output, pullup, pulldown, and enables hold feature for an RTC IO. Use this option if an RTC IO needs to be disconnected from internal circuits in deep sleep, to minimize leakage current.
-`pull`, boolean, whether to keep powering previously-configured internal pullup/pulldown resistors. Default is `false` if not specified.
-`touch`, boolean, whether to trigger wakeup from any previously-configured touchpads. Default is `false` if not specified.
If an empty options table is specified, ie no wakeup sources, then the chip will sleep forever with no way to wake it (except for power cycling or triggering the reset pin/button).
-`type`: type is either string "long" or "short". long: press the key for 3 seconds, short: press shortly(less than 3 seconds)
-`function`: user defined function which is called when key is pressed. If nil, remove the user defined function. Default function: long: change LED blinking rate, short: reset chip
Do **not** attempt to `print()` or otherwise induce the Lua interpreter to produce output from within the callback function. Doing so results in infinite recursion, and leads to a watchdog-triggered restart.
-`output_fn(str)` a function accept every output as str, and can send the output to a socket (or maybe a file). `nil` to unregister the previous function.
-`serial_output` 1 output also sent out the serial port. 0: no serial output. Defaults to 1 if not specified.
Redirects the debugging output from the Espressif SDK to a callback function allowing it to be captured or processed in Lua.
####Syntax
`node.osoutput(function(str))`
#### Parameters
-`function(str)` a function accepts debugging output as str, and can send the output to a socket (or maybe a file). `nil` to unregister the previous function.
Enters light sleep mode, which saves power without losing state. The state of the CPU and peripherals is preserved during light sleep and is resumed once the processor wakes up. When the processor wakes back up depends on the supplied `options`. Wake up from light sleep can be triggered by a time period, or when a GPIO (or GPIOs) change level, when a touchpad event occurs, when data is received on a UART, or by the ULP (ultra low power processor, generally not used by NodeMCU). If multiple different wakeup sources are specified, the processor will wake when any of them occur. The return value of the function can be used to determine which source caused the wakeup. The function does not return until a wakeup occurs (and therefore may not return at all if a wakeup trigger never happens).
UART buffers are not flushed on entering light sleep, rather they are suspended and resumed on wakeup, meaning that some data written before entering light sleep may not be output over the UART until after wakeup.
Timers created with `tmr` will not fire during light sleep, and the time spent sleeping is not factored in to their remaining time after wakeup. They are paused, and resumed automatically after wakeup. For example, if a timer has 2 seconds remaining when light sleep starts, it will still have 2 seconds remaining after wakeup, regardless of how much time elapsed during the sleep or what triggered the wakeup. The value returned by [`node.uptime()`](#nodeuptime) however _is_ updated by however long is spent in light sleep, and can therefore be used to calculate how much time was spent asleep.
Although a time period to sleep for can be specified in microseconds, the actual amount of time spent asleep will not be that precise.
Unlike with the [`dsleep()`](#nodedsleep) API, _any_ GPIO (not just the RTC-capable pins) may be used to trigger wakeup from light sleep. To configure which GPIOs should trigger wakeup, and under what circumstances, call [`gpio.wakeup()`](gpio.md#gpiowakeup) prior to calling `node.sleep()`. If a GPIO wakeup occurs, then any callbacks configured with [`gpio.trig()`](gpio.md#gpiotrig) will be called as normal after wakeup. In other words, interrupts do not get 'lost' during light sleep, and all other state such as pullups and drive strength is preserved.
Similarly, if `touch = true` is specified and a touch event triggers wakeup, the touch callback will be called as normal after wakeup.
Wakeup from light sleep can also be triggered by incoming data on UART0 or UART1, (but not UART2) by passing in `uart = 0` or `uart = 1` (or `uart = {0, 1}` to wake on either). Note that the byte(s) which trigger the wakeup are consumed in the process, and will therefore not be seen by the UART after wakeup. Before using uart wakeup for the first time, you must call [`uart.wakeup()`](uart.md#uartwakeup) to configure what data should trigger wakeup.
WiFi and Bluetooth must be switched off before entering light sleep, otherwise an error will be thrown.
#### Syntax
`node.sleep(options)`
#### Parameters
-`options`, a table containing some of:
-`secs`, a number of seconds to sleep. This permits longer sleep periods compared to using the `us` parameter.
-`us`, a number of microseconds to sleep. If both `secs` and `us` are provided, the values are combined.
-`gpio`, a boolean, whether to allow wakeup by GPIOs. Default is `false` if not specified.
-`touch`, boolean, whether to trigger wakeup from any previously-configured touchpads. Default is `false` if not specified.
-`uart`, an integer or list of integers. Which UARTs should trigger wakeup. Default is the empty list if not specified.
-`ulp`, a boolean, whether to allow the ULP to trigger wakeup. Default is `false` if not specified.
If an empty options table is specified, ie no wakeup sources, then the chip will light sleep forever with no way to wake it (except for power cycling or triggering the reset pin/button).
#### Returns
One of the following values, depending on what triggered the wakeup.
-`node.wakeup.GPIO`
-`node.wakeup.TIMER`
-`node.wakeup.TOUCHPAD`
-`node.wakeup.UART`
-`node.wakeup.ULP`
#### Example
```lua
-- sleep 10 seconds then continue
node.sleep({ secs = 10 })
-- sleep until 10 seconds have elapsed or either of GPIO 13 or 15 becomes high
gpio.wakeup(13, gpio.INTR_HIGH)
gpio.wakeup(15, gpio.INTR_HIGH)
node.sleep({ secs = 10, gpio = true })
-- Sleep forever until a previously-configured touchpad is touched, or a byte
Controls the amount of debug information kept during [`node.compile()`](#nodecompile), and allows removal of debug information from already compiled Lua code.
If no arguments are given then the current default setting is returned. If function is omitted, this is the default setting for future compiles. The function argument uses the same rules as for `setfenv()`.
Returns the value of the system counter, which counts in microseconds starting at 0 when the device is booted. Because a 32-bit signed integer can only fit 35 minutes' worth of microseconds before wrapping, when using integer-only 32-bit Lua this API returns 2 results, the first being the bottom 31 bits of the counter, and the second being the next 31 bits (ie bits 31 through 62 of the underlying 64-bit counter).
Therefore the first result will wrap back to 0 after about 35 minutes (2^31 microseconds), at which point the second result will increment by one. It is important to consider both values, or otherwise handle the first result wrapping, when for example using this function to [debounce or throttle GPIO input](https://github.com/hackhitchin/esp8266-co-uk/issues/2).
When using floating-point Lua, hundreds of years of microseconds can fit in a single value with no loss of precision. In such configurations, the first result will be the bottom 53 bits of the system counter as a floating-point number, and the second result will be the top 11 bits, which in practice will always be zero unless the system counter exceeds 285 years.
#### Syntax
`node.uptime()`
#### Parameters
none
#### Returns
Two results `lowbits, highbits`. The first is the time in microseconds since boot or the last time the counter wrapped, and the second is the number of times the counter has wrapped. Depending on whether Lua was compiled with floating-point support or not determines when the counter wraps.
#### Example
```lua
print(node.uptime())
print(node.uptime())
lowbits, highbits = node.uptime()
print(lowbits, "microseconds have elapsed since the uptime last wrapped")
print(string.format("Uptime has wrapped %d times", highbits))
-`node.egc.NOT_ACTIVE` EGC inactive, no collection cycle will be forced in low memory situations
-`node.egc.ON_ALLOC_FAILURE` Try to allocate a new block of memory, and run the garbage collector if the allocation fails. If the allocation fails even after running the garbage collector, the allocator will return with error.
-`node.egc.ON_MEM_LIMIT` Run the garbage collector when the memory used by the Lua script goes beyond an upper `limit`. If the upper limit can't be satisfied even after running the garbage collector, the allocator will return with error.
-`node.egc.ALWAYS` Run the garbage collector before each memory allocation. If the allocation fails even after running the garbage collector, the allocator will return with error. This mode is very efficient with regards to memory savings, but it's also the slowest.
-`level` in the case of `node.egc.ON_MEM_LIMIT`, this specifies the memory limit.
