nodemcu-firmware/docs/en/modules/gpio.md

GPIO Module

Since	Origin / Contributor	Maintainer	Source
2014-12-22	Zeroday	Zeroday	gpio.c

This module provides access to the GPIO (General Purpose Input/Output) subsystem.

All access is based on the I/O index number on the NodeMCU dev kits, not the internal GPIO pin. For example, the D0 pin on the dev kit is mapped to the internal GPIO pin 16.

If not using a NodeMCU dev kit, please refer to the below GPIO pin maps for the index↔gpio mapping.

IO index	ESP8266 pin	IO index	ESP8266 pin
0 [*]	GPIO16	7	GPIO13
1	GPIO5	8	GPIO15
2	GPIO4	9	GPIO3
3	GPIO0	10	GPIO1
4	GPIO2	11	GPIO9
5	GPIO14	12	GPIO10
6	GPIO12

** [*] D0(GPIO16) can only be used as gpio read/write. No support for open-drain/interrupt/pwm/i2c/ow. **

gpio.mode()

Initialize pin to GPIO mode, set the pin in/out direction, and optional internal weak pull-up.

Syntax

gpio.mode(pin, mode [, pullup])

Parameters

• pin pin to configure, IO index
• mode one of gpio.OUTPUT, gpio.OPENDRAIN, gpio.INPUT, or gpio.INT (interrupt mode)
• pullup gpio.PULLUP enables the weak pull-up resistor; default is gpio.FLOAT

Returns

nil

Example

gpio.mode(0, gpio.OUTPUT)

See also

• gpio.read()
• gpio.write()

gpio.read()

Read digital GPIO pin value.

Syntax

gpio.read(pin)

Parameters

pin pin to read, IO index

Returns

a number, 0 = low, 1 = high

Example

-- read value of gpio 0.
gpio.read(0)

See also

gpio.mode()

gpio.serout()

Serialize output based on a sequence of delay-times in µs. After each delay, the pin is toggled. After the last cycle and last delay the pin is not toggled.

The function works in two modes:

• synchronous - for sub-50 µs resolution, restricted to max. overall duration,
• asynchrounous - synchronous operation with less granularity but virtually unrestricted duration.

Whether the asynchronous mode is chosen is defined by presence of the callback parameter. If present and is of function type the function goes asynchronous and the callback function is invoked when sequence finishes. If the parameter is numeric the function still goes asynchronous but no callback is invoked when done.

For the asynchronous version, the minimum delay time should not be shorter than 50 μs and maximum delay time is 0x7fffff μs (~8.3 seconds). In this mode the function does not block the stack and returns immediately before the output sequence is finalized. HW timer FRC1_SOURCE mode is used to change the states. As there is only a single hardware timer, there are restrictions on which modules can be used at the same time. An error will be raised if the timer is already in use.

Note that the synchronous variant (no or nil callback parameter) function blocks the stack and as such any use of it must adhere to the SDK guidelines (also explained here). Failure to do so may lead to WiFi issues or outright to crashes/reboots. In short it means that the sum of all delay times multiplied by the number of cycles should not exceed 15 ms.

Syntax

gpio.serout(pin, start_level, delay_times [, cycle_num[, callback]])

Parameters

• pin pin to use, IO index
• start_level level to start on, either gpio.HIGH or gpio.LOW
• delay_times an array of delay times in µs between each toggle of the gpio pin.
• cycle_num an optional number of times to run through the sequence. (default is 1)
• callback an optional callback function or number, if present the function returns immediately and goes asynchronous.

Returns

nil

Example

gpio.mode(1,gpio.OUTPUT,gpio.PULLUP)
gpio.serout(1,gpio.HIGH,{30,30,60,60,30,30})  -- serial one byte, b10110010
gpio.serout(1,gpio.HIGH,{30,70},8)  -- serial 30% pwm 10k, lasts 8 cycles
gpio.serout(1,gpio.HIGH,{3,7},8)  -- serial 30% pwm 100k, lasts 8 cycles
gpio.serout(1,gpio.HIGH,{0,0},8)  -- serial 50% pwm as fast as possible, lasts 8 cycles
gpio.serout(1,gpio.LOW,{20,10,10,20,10,10,10,100}) -- sim uart one byte 0x5A at about 100kbps
gpio.serout(1,gpio.HIGH,{8,18},8) -- serial 30% pwm 38k, lasts 8 cycles

gpio.serout(1,gpio.HIGH,{5000,995000},100, function() print("done") end) -- asynchronous 100 flashes 5 ms long every second with a callback function when done
gpio.serout(1,gpio.HIGH,{5000,995000},100, 1) -- asynchronous 100 flashes 5 ms long, no callback

gpio.trig()

Establish or clear a callback function to run on interrupt for a pin.

This function is not available if GPIO_INTERRUPT_ENABLE was undefined at compile time.

Syntax

gpio.trig(pin, [type [, callback_function]])

Parameters

• pin 1-12, pin to trigger on, IO index. Note that pin 0 does not support interrupts.
• type "up", "down", "both", "low", "high", which represent rising edge, falling edge, both edges, low level, and high level trigger modes respectivey. If the type is "none" or omitted then the callback function is removed and the interrupt is disabled.
• callback_function(level, when, eventcount) callback function when trigger occurs. The level of the specified pin at the interrupt passed as the first parameter to the callback. The timestamp of the event is passed as the second parameter. This is in microseconds and has the same base as for tmr.now(). This timestamp is grabbed at interrupt level and is more consistent than getting the time in the callback function. This timestamp is normally of the first interrupt detected, but, under overload conditions, might be a later one. The eventcount is the number of interrupts that were elided for this callback. This works best for edge triggered interrupts and enables counting of edges. However, beware of switch bounces -- you can get multiple pulses for a single switch closure. Counting works best when the edges are digitally generated. The previous callback function will be used if the function is omitted.

Returns

nil

Example

do
  -- use pin 1 as the input pulse width counter
  local pin, pulse1, du, now, trig = 1, 0, 0, tmr.now, gpio.trig
  gpio.mode(pin,gpio.INT)
  local function pin1cb(level, pulse2)
    print( level, pulse2 - pulse1 )
    pulse1 = pulse2
    trig(pin, level == gpio.HIGH  and "down" or "up")
  end
  trig(pin, "down", pin1cb)
end

See also

gpio.mode()

gpio.write()

Set digital GPIO pin value.

Syntax

gpio.write(pin, level)

Parameters

• pin pin to write, IO index
• level gpio.HIGH or gpio.LOW

Returns

nil

Example

-- set pin index 1 to GPIO mode, and set the pin to high.
pin=1
gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, gpio.HIGH)

See also

• gpio.mode()
• gpio.read()

gpio.pulse

This covers a set of APIs that allow generation of pulse trains with accurate timing on multiple pins. It is similar to the serout API, but can handle multiple pins and has better timing control.

The basic idea is to build a gpio.pulse object and then control it with methods on that object. Only one gpio.pulse object can be active at a time. The object is built from an array of tables where each inner table represents an action to take and the time to delay before moving to the next action.

One of the uses for this is to generate bipolar impulse for driving clock movements where you want (say) a pulse on Pin 1 on the even second, and a pulse on Pin 2 on the odd second. :getstate and :adjust can be used to keep the pulse synchronized to the RTC clock (that is itself synchronized with NTP).

!!! Configuration This feature is only available if LUA_USE_MODULES_GPIO_PULSE is defined at build time.

gpio.pulse.build

This builds the gpio.pulse object from the supplied argument -- which is a table as described below.

Syntax

gpio.pulse.build(table)

Parameter

table this is view as an array of instructions. Each instruction is represented by a table as follows:

• All numeric keys are considered to be pin numbers. The values of each are the value to be set onto the respective GPIO line. For example { [1] = gpio.HIGH } would set pin 1 to be high. Note this that is the pin number and not the GPIO number. Multiple pins can be set at the same time.
• delay specifies the number of microseconds after setting the pin values to wait until moving to the next state. The actual delay may be longer than this value depending on whether interrupts are enabled at the end time.
• min and max can be used to specify (along with delay) that this time can be varied. If one time interval overruns, then the extra time will be deducted from a time period which has a min or max specified. The actual time can also be adjusted with the :adjust API below.
• count and loop allow simple looping. When a state with count and loop is completed, the next state is at loop (provided that count has not decremented to zero). The first state is state 1.

Returns

gpio.pulse object.

Example

gpio.mode(1,gpio.OUTPUT,gpio.PULLUP)
gpio.mode(2,gpio.OUTPUT,gpio.PULLUP)

pulser = gpio.pulse.build( {
  { [1] = gpio.HIGH, [2] = gpio.LOW, delay=100000 },
  { [1] = gpio.LOW, [2] = gpio.HIGH, delay=100000, loop=1, count=100, min=90000, max=110000 }
})

gpio.pulse:start

This starts the output operations.

Syntax

pulser:start([adjust, ] callback)

Parameter

• adjust This is the number of microseconds to add to the next adjustable period. If this value is so large that it would push the delay past the min or max, then the remainder is held over until the next adjustable period.
• callback This callback is executed when the pulses are complete. The callback is invoked with the same four parameters that are described as the return values of gpio.pulse:getstate.

Returns

nil

Example

pulser:start(function(pos, steps, offset, now)
             print (pos, steps, offset, now)
             end)

gpio.pulse:getstate

This returns the current state. These four values are also passed into the callback functions.

Syntax

pulser:getstate()

Returns

• position is the index of the currently active state. The first state is state 1. This is nil if the output operation is complete.
• steps is the number of states that have been executed (including the current one). This allows monitoring of progress when there are loops.
• offset is the time (in microseconds) until the next state transition. This will be negative once the output operation is complete.
• now is the value of the tmr.now() function at the instant when the offset was calculated.

Example

pos, steps, offset, new = pulser:getstate()
print (pos, steps, offset, now)

gpio.pulse:stop

This stops the output operation at some future time.

Syntax

pulser:stop([position ,] callback)

Parameters

• position is the index to stop at. The stopping happens on entry to this state. If not specified, then stops on the next state transition.
• callback is invoked (with the same arguments as are returned by :getstate) when the operation has been stopped.

Returns

true if the stop will happen.

Example

pulser:stop(function(pos, steps, offset, now)
            print (pos, steps, offset, now)
            end)

gpio.pulse:cancel

This stops the output operation immediately.

Syntax

pulser:cancel()

Returns

• position is the index of the currently active state. The first state is state 1. This is nil if the output operation is complete.
• steps is the number of states that have been executed (including the current one). This allows monitoring of progress when there are loops.
• offset is the time (in microseconds) until the next state transition. This will be negative once the output operation is complete.
• now is the value of the tmr.now() function at the instant when the offset was calculated.

Example

pulser:cancel(function(pos, steps, offset, now)
              print (pos, steps, offset, now)
              end)

gpio.pulse:adjust

This adds (or subtracts) time that will get used in the min / max delay case. This is useful if you are trying to synchronize a particular state to a particular time or external event.

Syntax

pulser:adjust(offset)

Parameters

• offset is the number of microseconds to be used in subsequent min / max delays. This overwrites any pending offset.

Returns

• position is the index of the currently active state. The first state is state 1. This is nil if the output operation is complete.
• steps is the number of states that have been executed (including the current one). This allows monitoring of progress when there are loops.
• offset is the time (in microseconds) until the next state transition. This will be negative once the output operation is complete.
• now is the value of the tmr.now() function at the instant when the offset was calculated.

Example

pulser:adjust(177)