EM.GPIO 0.0.6
A module to control EM GPIO channels
License: MIT
Keywords: EM GPIO

# Installation

## Using pip

The easiest way to install this library is using `pip`:
```shell
sudo pip install EM.GPIO
```

# Complete library API

The EM GPIO library provides all public APIs provided by the RPi.GPIO
library. The following discusses the use of each API:

#### 1. Importing the libary

To import the EM.GPIO module use:
```python
import EM.GPIO as GPIO
```

This way, you can refer to the module as GPIO throughout the rest of the
application. The module can also be imported using the name RPi.GPIO instead of
EM.GPIO for existing code using the RPi library.

#### 2. Pin numbering

| BOARD ch | BCM ch | function |
| :------:| :-----: | --------|
| 15  | 22 | LCD_RST |
| 29  | 5 | LCD_R/S  |
| 24  | 8 | LCD_CS  |
| 40  | 21 | Charger OTG |
| 38  | 20 | Charger PROCHOT |
| 35  | 19 | Charger CMPOUT |
| 18  | 24 | VOL-  |
| 26  | 7 | VOL+  |
| 41  | 41 | BACK |
| 42  | 42 | OK |
| 43  | 43 | HOME |
| 13  | 27 | LED_R |
| 22  | 25 | LED_B |
| 37  | 26 | LED_G |
| 44  | 44 | BEEP |
| 16  | 23 | MOTOR |
| 45  | 45 | LED_Brightness_EN |
| 36 | 16 | GD32 Boot select |
| 11 | 17 | GD32 Hard reset |

To specify which mode you are using (mandatory), use the following function
call:
```python
GPIO.setmode(GPIO.BOARD)

To check which mode has be set, you can call:
```python
mode = GPIO.getmode()
```

The mode must be one of GPIO.BOARD, GPIO.BCM, GPIO.CVM, GPIO.TEGRA_SOC or
None.

#### 3. Warnings

It is possible that the GPIO you are trying to use is already being used
external to the current application. In such a condition, the Jetson GPIO
library will warn you if the GPIO being used is configured to anything but the
default direction (input). It will also warn you if you try cleaning up before
setting up the mode and channels. To disable warnings, call:
```python
GPIO.setwarnings(False)
```

#### 4. Set up a channel

The GPIO channel must be set up before use as input or output. To configure
the channel as input, call:
```python
# (where channel is based on the pin numbering mode discussed above)
GPIO.setup(channel, GPIO.IN)
```

To set up a channel as output, call:
```python
GPIO.setup(channel, GPIO.OUT)
```

It is also possible to specify an initial value for the output channel:
```python
GPIO.setup(channel, GPIO.OUT, initial=GPIO.HIGH)
```

When setting up a channel as output, it is also possible to set up more than one
channel at once:
```python
# add as many as channels as needed. You can also use tuples: (18,12,13)
channels = [18, 12, 13]
GPIO.setup(channels, GPIO.OUT)
```

#### 5. Input

To read the value of a channel, use:

```python
GPIO.input(channel)
```

This will return either GPIO.LOW or GPIO.HIGH.

#### 6. Output

To set the value of a pin configured as output, use:

```python
GPIO.output(channel, state)
```

where state can be GPIO.LOW or GPIO.HIGH.

You can also output to a list or tuple of channels:

```python
channels = [18, 12, 13] # or use tuples
GPIO.output(channels, GPIO.HIGH) # or GPIO.LOW
# set first channel to LOW and rest to HIGH
GPIO.output(channel, (GPIO.LOW, GPIO.HIGH, GPIO.HIGH))
```

#### 7. Clean up

At the end of the program, it is good to clean up the channels so that all pins
are set in their default state. To clean up all channels used, call:

```python
GPIO.cleanup()
```

If you don't want to clean all channels, it is also possible to clean up
individual channels or a list or tuple of channels:

```python
GPIO.cleanup(chan1) # cleanup only chan1
GPIO.cleanup([chan1, chan2]) # cleanup only chan1 and chan2
GPIO.cleanup((chan1, chan2))  # does the same operation as previous statement
```

#### 8. Jetson Board Information and library version

To get information about the Jetson module, use/read:

```python
GPIO.JETSON_INFO
```

This provides a Python dictionary with the following keys: P1_REVISION, RAM,
REVISION, TYPE, MANUFACTURER and PROCESSOR. All values in the dictionary are
strings with the exception of P1_REVISION which is an integer.

To get information about the library version, use/read:

```python
GPIO.VERSION
```

This provides a string with the X.Y.Z version format.

#### 9. Interrupts

Aside from busy-polling, the library provides three additional ways of
monitoring an input event:

##### The wait_for_edge() function

This function blocks the calling thread until the provided edge(s) is
detected. The function can be called as follows:

```python
GPIO.wait_for_edge(channel, GPIO.RISING)
```

The second parameter specifies the edge to be detected and can be
GPIO.RISING, GPIO.FALLING or GPIO.BOTH. If you only want to limit the wait
to a specified amount of time, a timeout can be optionally set:

```python
# timeout is in milliseconds
GPIO.wait_for_edge(channel, GPIO.RISING, timeout=500)
```

The function returns the channel for which the edge was detected or None if a
timeout occurred.

##### The event_detected() function

This function can be used to periodically check if an event occurred since the
last call. The function can be set up and called as follows:

```python
# set rising edge detection on the channel
GPIO.add_event_detect(channel, GPIO.RISING)
run_other_code()
if GPIO.event_detected(channel):
    do_something()
```

As before, you can detect events for GPIO.RISING, GPIO.FALLING or GPIO.BOTH.

##### A callback function run when an edge is detected

This feature can be used to run a second thread for callback functions. Hence,
the callback function can be run concurrent to your main program in response
to an edge. This feature can be used as follows:

```python
# define callback function
def callback_fn(channel):
    print("Callback called from channel %s" % channel)

# add rising edge detection
GPIO.add_event_detect(channel, GPIO.RISING, callback=callback_fn)
```

More than one callback can also be added if required as follows:

```python
def callback_one(channel):
    print("First Callback")

def callback_two(channel):
    print("Second Callback")

GPIO.add_event_detect(channel, GPIO.RISING)
GPIO.add_event_callback(channel, callback_one)
GPIO.add_event_callback(channel, callback_two)
```

The two callbacks in this case are run sequentially, not concurrently since
there is only thread running all callback functions.

In order to prevent multiple calls to the callback functions by collapsing
multiple events in to a single one, a debounce time can be optionally set:

```python
# bouncetime set in milliseconds
GPIO.add_event_detect(channel, GPIO.RISING, callback=callback_fn,
bouncetime=200)
```

If the edge detection is not longer required it can be removed as follows:

```python
GPIO.remove_event_detect(channel)
```

#### 10. Check function of GPIO channels

This feature allows you to check the function of the provided GPIO channel:

```python
GPIO.gpio_function(channel)
```

The function returns either GPIO.IN or GPIO.OUT.

#### 11. PWM

See `samples/simple_pwm.py` for details on how to use PWM channels.

The Jetson.GPIO library supports PWM only on pins with attached hardware PWM
controllers. Unlike the RPi.GPIO library, the Jetson.GPIO library does not
implement Software emulated PWM. Jetson Nano supports 2 PWM channels, and
Jetson AGX Xavier supports 3 PWM channels. Jetson TX1 and TX2 do not support
any PWM channels.

The system pinmux must be configured to connect the hardware PWM controlller(s)
to the relevant pins. If the pinmux is not configured, PWM signals will not
reach the pins! The Jetson.GPIO library does not dynamically modify the pinmux
configuration to achieve this. Read the L4T documentation for details on how to
configure the pinmux.


jarius@163.com