open-drop 0.2.post21

Arduino RPC node packaged as Python package.

# open-drop # Control package for OpenDrop Digital Microfluidics Platform

## Overview ##

This package contains:

• Firmware compatible with Arduino Uno or Mega2560.

• Installable Python package for interfacing with Arduino firmware through serial port or i2c (through a serial-to-i2c proxy).

## Install ##

The Python package can be installed through pip using the following command:

pip install open-drop

## Upload firmware ##

To upload the pre-compiled firmware included in the Python package, run the following command:

python -m open_drop.bin.upload <board type>

replacing <board type> with either uno or mega2560, depending on the model of the board.

This will attempt to upload the firmware by automatically discovering the serial port. On systems with multiple serial ports, use the -p command line argument to specify the serial port to use. For example:

python -m open_drop.bin.upload -p COM3 uno

---

## Usage ##

After uploading the firmware to the board, the open_drop.Proxy class can be used to interact with the Arduino device.

See the session log below for example usage.

### Example interactive session ###

>>> from serial import Serial
>>> from open_drop import Proxy

Connect to serial device.

>>> serial_device = Serial('/dev/ttyUSB0', baudrate=115200)

Initialize a device proxy using existing serial connection.

>>> proxy = Proxy(serial_device)

Query the number of bytes free in device RAM.

>>> proxy.ram_free()
409

Query descriptive properties of device.

>>> proxy.properties()
base_node_software_version                               0.9.post8.dev141722557
name                                                                  open_drop
manufacturer                                                        Wheeler Lab
url                           http://github.com/wheeler-microfluidics/open-d...
software_version                                                            0.1
dtype: object

Use Arduino API methods interactively.

>>> # Set pin 13 as output
>>> proxy.pin_mode(13, 1)
>>> # Turn led on
>>> proxy.digital_write(13, 1)
>>> # Turn led off
>>> proxy.digital_write(13, 0)

Query number of available channels.

>>> proxy.channel_count()
40

Query state of channels array.

>>> proxy.state_of_channels
array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], dtype=uint8)

Turn on every other channel.

>>> proxy.state_of_channels = 20 * [0, 1]

Query updated state of channels array.

>>> proxy.state_of_channels
array([0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
       1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1], dtype=uint8)

### Configuration and state ###

The device stores a configuration and a state. The configuration is serialized and stored in EEPROM, allowing settings to persist across device resets. The state is stored in device memory and is reinitialized each time the device starts up.

Print (non-default) configuration values.

>>> print proxy.config
serial_number: 2
baud_rate: 115200
i2c_address: 17

>>> proxy.config.
proxy.config.max_waveform_frequency  proxy.config.max_waveform_voltage
>>> proxy.config.max_waveform_voltage
200
>>> proxy.config.max_waveform_frequency
10000

Set voltage and frequency.

>>> result_code = proxy.update_state(voltage=100, frequency=1e3)
>>> print proxy.state
voltage: 100.0
frequency: 1000.0

#### Validation ####

Note that negative values are not allowed for voltage or frequency.

>>> result_code = proxy.update_state(voltage=-1)  # Negative voltage
>>> print proxy.state
voltage: 100.0
frequency: 1000.0

Voltage/frequency updates are restricted to allowable range.

>>> result_code = proxy.update_state(voltage=300)  # Voltage greater than max
>>> print proxy.state  # Voltage remains unchanged
voltage: 100.0
frequency: 1000.0

Max values can be increased by updating the configuration.

>>> result_code = proxy.update_config(max_waveform_voltage=300)
>>> result_code = proxy.update_state(voltage=300)  # Voltage now <= max
>>> print proxy.state  # Voltage changed
voltage: 300.0
frequency: 1000.0

To persist changes to configuration across device reset - not state - use save_config method.

>>> proxy.save_config()

### Other methods ###

Below is a list of the attributes of the open_drop.Proxy Python class. Note that many of the [Arduino API][1] functions (e.g., pin_mode, digital_write, etc.) are exposed through the RPC API.

>>> proxy.
proxy.analog_read                      proxy.microseconds
proxy.analog_write                     proxy.milliseconds
proxy.array_length                     proxy.name
proxy.base_node_software_version       proxy.on_config_baud_rate_changed
proxy.begin                            proxy.on_config_i2c_address_changed
proxy.buffer_size                      proxy.on_config_serial_number_changed
proxy.channel_count                    proxy.on_state_frequency_changed
proxy.config                           proxy.on_state_voltage_changed
proxy.delay_ms                         proxy.pin_mode
proxy.delay_us                         proxy.properties
proxy.digital_read                     proxy.ram_free
proxy.digital_write                    proxy.read_eeprom_block
proxy.echo_array                       proxy.reset_config
proxy.get_buffer                       proxy.reset_state
proxy.i2c_address                      proxy.save_config
proxy.i2c_available                    proxy.serialize_config
proxy.i2c_buffer_size                  proxy.serialize_state
proxy.i2c_read                         proxy.set_i2c_address
proxy.i2c_read_byte                    proxy.set_state_of_channels
proxy.i2c_request                      proxy.software_version
proxy.i2c_request_from                 proxy.state
proxy.i2c_scan                         proxy.state_of_channels
proxy.i2c_write                        proxy.str_echo
proxy.load_config                      proxy.update_config
proxy.manufacturer                     proxy.update_eeprom_block
proxy.max_i2c_payload_size             proxy.update_state
proxy.max_serial_payload_size          proxy.url

---

## Firmware development ##

The Arduino firmware/sketch is located in the open_drop/Arduino/open_drop directory. The key functionality is defined in the open_drop::Node class in the file Node.h.

Running the following command will build the firmware using [SCons][2] for Arduino Uno and Arduino Mega2560, and will package the resulting firmware in a Python package, ready for distribution.

paver sdist

### Adding new remote procedure call (RPC) methods ###

New methods may be added to the RPC API by adding new methods to the open_drop::Node class in the file Node.h.

# Author #

Copyright 2015 Christian Fobel <[e-mail]>

[1]: https://www.arduino.cc/en/Reference/HomePage [2]: http://www.scons.org/