USB ISS Python Module¶

Contents¶

USB-ISS Python Library¶

Python library for the USB-ISS module.

Documentation¶

USB-ISS hardware module:: https://www.robot-electronics.co.uk/htm/usb_iss_tech.htm
USB-ISS Python library (this project):: https://usb-iss.readthedocs.io

Features¶

Supports all USB-ISS functions (I2C, IO, SPI, Serial)
Cross-platform (Windows, Linux, MacOS, BSD)
Comprehensive documentation and unit test suite

Usage Example¶

from usb_iss import UsbIss, defs

# Configure I2C mode

iss = UsbIss()
iss.open("COM3")
iss.setup_i2c()

# Write and read back some data
# NOTE: I2C methods use 7-bit device addresses (0x00 - 0x7F)

iss.i2c.write(0x62, 0, [0, 1, 2]);
data = iss.i2c.read(0x62, 0, 3)

print(data)
# [0, 1, 2]

Installing¶

pip install usb-iss

This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.

usb_iss package¶

class usb_iss.UsbIss(dummy=False, verbose=False)[source]¶

Bases: object

Main object used to interact with the USB_ISS device.

Example

from usb_iss import UsbIss, defs

# Configure I2C mode

iss = UsbIss()
iss.open("COM3")
iss.setup_i2c()

# Write and read back some data
# NOTE: I2C methods use 7-bit device addresses (0x00 - 0x7F)

iss.i2c.write(0x62, 0, [0, 1, 2]);
data = iss.i2c.read(0x62, 0, 3)

print(data)
# [0, 1, 2]

Parameters

dummy (bool) – Use a dummy driver stub, for testing.
verbose (bool) – Print debug output to the console.

i2c¶

Attribute to use for I2C access. See i2c.I2C for the full set of I2C methods.

Type: i2c.I2C

io¶

Attribute to use for pin IO access. See io.IO for the full set of IO methods.

Type: io.IO

spi¶

Attribute to use for SPI access. See spi.SPI for the full set of SPI methods.

Type: spi.SPI

serial¶

Attribute to use for Serial UART access. See serial_.Serial for the full set of Serial methods.

Type: serial_.Serial

open(port)[source]¶

Open the specified serial port for communication with the USB_ISS module.

Parameters: port (str) – Serial port to use for usb_iss communication.

close()[source]¶: Close the serial port.

setup_i2c(clock_khz=400, use_i2c_hardware=True, io1_type=None, io2_type=None)[source]¶

Issue an ISS_MODE command to set the operating mode to I2C + IO.

Parameters

clock_khz (int) – I2C clock rate in kHz. See https://www.robot-electronics.co.uk/htm/usb_iss_tech.htm for a list of valid values.
use_i2c_hardware (bool) – Use the USB_ISS module’s hardware I2C controller.
io1_type (defs.IOType) – IO1 mode (or None for no change)
io2_type (defs.IOType) – IO2 mode (or None for no change)

setup_i2c_serial(clock_khz=400, use_i2c_hardware=True, baud_rate=9600)[source]¶

Issue an ISS_MODE command to set the operating mode to I2C + Serial.

Parameters

clock_khz (int) – I2C clock rate in kHz. See https://www.robot-electronics.co.uk/htm/usb_iss_tech.htm for a list of valid values.
use_i2c_hardware (bool) – Use the USB_ISS module’s hardware I2C controller.
baud_rate (int) – Baud rate for the serial interface.

setup_spi(spi_mode=<SPIMode.TX_ACTIVE_TO_IDLE_IDLE_LOW: 144>, clock_khz=500)[source]¶

Issue an ISS_MODE command to set the operating mode to SPI.

Parameters

spi_mode (defs.SPIMode) – SPI mode option to use.
clock_khz (int) – SPI clock rate in kHz.

setup_io(io1_type=None, io2_type=None, io3_type=None, io4_type=None)[source]¶

Issue an ISS_MODE command to set the operating mode to IO.

Parameters

io1_type (defs.IOType) – IO1 mode (or None for no change)
io2_type (defs.IOType) – IO2 mode (or None for no change)
io3_type (defs.IOType) – IO3 mode (or None for no change)
io4_type (defs.IOType) – IO4 mode (or None for no change)

change_io(io1_type=None, io2_type=None, io3_type=None, io4_type=None)[source]¶

Issue an ISS_MODE command to change the current IO mode without affecting serial or I2C settings.

Parameters

io1_type (defs.IOType) – IO1 mode (or None for no change)
io2_type (defs.IOType) – IO2 mode (or None for no change)
io3_type (defs.IOType) – IO3 mode (or None for no change)
io4_type (defs.IOType) – IO4 mode (or None for no change)

setup_serial(baud_rate=9600, io3_type=None, io4_type=None)[source]¶

Issue an ISS_MODE command to set the operating mode to Serial + IO.

Parameters

baud_rate (int) – Baud rate for the serial interface.
io3_type (defs.IOType) – IO3 mode (or None for no change)
io4_type (defs.IOType) – IO4 mode (or None for no change)

read_module_id()[source]¶

Returns: The USB_ISS module ID (always 7).
Return type: int

read_fw_version()[source]¶

Returns: The USB_ISS firmware version.
Return type: int

read_iss_mode()[source]¶

Returns: The current ISS_MODE operating mode.
Return type: defs.Mode

read_serial_number()[source]¶

Returns: The serial number of the attached USB_ISS module.
Return type: str

exception usb_iss.UsbIssError[source]¶

Bases: Exception

Raised when an error condition is detected by the usb_iss library.

usb_iss.i2c module¶

class usb_iss.i2c.I2C(drv)[source]¶

Bases: object

Use the USB_ISS device to perform I2C accesses.

Example

from usb_iss import UsbIss, defs

# Configure I2C mode

iss = UsbIss()
iss.open("COM3")
iss.setup_i2c()

# Write and read back some data
# NOTE: I2C methods use 7-bit device addresses (0x00 - 0x7F)

iss.i2c.write(0x62, 0, [0, 1, 2]);
data = iss.i2c.read(0x62, 0, 3)

print(data)
# [0, 1, 2]

write(address, register, data)[source]¶

Write multiple bytes to a device with a one-byte internal register address. This is an alias for the write_ad1 method, used by the majority of devices.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
register (int) – Internal register address to write (0x00 - 0xFF).
data (list of int) – List of bytes to write to the device.

read(address, register, byte_count)[source]¶

Read multiple bytes from a device with a one-byte internal register address. This is an alias for the read_ad1 method, used by the majority of devices.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
register (int) – Internal register address to read (0x00 - 0xFF).
byte_count (int) – Number of bytes to read.

Returns

List of bytes read from the device.

Return type

list of int

write_single(address, data_byte)[source]¶

Write a single byte to an I2C device.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
data_byte (int) – Data byte to write to the device.

read_single(address)[source]¶

Read a single byte from an I2C device.

Parameters: address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
Returns: Data byte read from the device.
Return type: int

write_ad0(address, data)[source]¶

Write multiple bytes to a device without internal register addressing, or where the internal register address does not require resetting.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
data (list of int) – List of bytes to write to the device.

read_ad0(address, byte_count)[source]¶

Read multiple bytes from a device without internal register addressing, or where the internal register address does not require resetting.

Parameters

address (int) – 7-bit I2C address of the device.
byte_count (int) – Number of bytes to read.

Returns

List of bytes read from the device.

Return type

list of int

write_ad1(address, register, data)[source]¶

Write multiple bytes to a device with a one-byte internal register address.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
register (int) – Internal register address to write (0x00 - 0xFF).
data (list of int) – List of bytes to write to the device.

read_ad1(address, register, byte_count)[source]¶

Read multiple bytes from a device with a one-byte internal register address.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
register (int) – Internal register address to read (0x00 - 0xFF).
byte_count (int) – Number of bytes to read.

Returns

List of bytes read from the device.

Return type

list of int

write_ad2(address, register, data)[source]¶

Write multiple bytes to a device with a two-byte internal register address.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
register (int) – Internal register address to write (0x0000 - 0xFFFF).
data (list of int) – List of bytes to write to the device.

read_ad2(address, register, byte_count)[source]¶

Read multiple bytes from a device with a two-byte internal register address.

Parameters

address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
register (int) – Internal register address to read (0x0000 - 0xFFFF).
byte_count (int) – Number of bytes to read.

Returns

List of bytes read from the device.

Return type

list of int

direct(data)[source]¶

Send a custom I2C sequence to the device. See https://www.robot-electronics.co.uk/htm/usb_iss_i2c_tech.htm for a full set of examples.

Parameters: data (list of defs.I2CDirect) – List of I2CDirect commands and data.
Returns: List of bytes read from the device.
Return type: list of int

Example

# Equivalent to iss.i2c.write_single(0x20, 0x55)
iss.i2c.direct([
    defs.I2CDirect.START,
    defs.I2CDirect.WRITE2,
    0x40,
    0x55,
    defs.I2CDirect.STOP,
]);

test(address)[source]¶

Check whether a device responds at the specified I2C addresss.

Parameters: address (int) – 7-bit I2C address of the device (0x00 - 0x7F).
Returns: True if the device responds with an ACK.
Return type: bool

usb_iss.io module¶

class usb_iss.io.IO(drv)[source]¶

Bases: object

Use the USB_ISS device to perform IO accesses.

Example

from usb_iss import UsbIss

# Configure IO mode with all outputs low

iss = UsbIss()
iss.open("COM3")
iss.setup_io(io1_type=defs.IOType.OUTPUT_LOW,
             io2_type=defs.IOType.OUTPUT_LOW,
             io3_type=defs.IOType.OUTPUT_LOW,
             io4_type=defs.IOType.OUTPUT_LOW)

# Drive IO1 & IO3 high
iss.io.set_pins(1, 0, 1, 0);

set_pins(io0, io1, io2, io3)[source]¶

Set the digital output pins high or low. This command only operates on pins that have been configured as digital outputs. Digital or analogue inputs or pins that are used for I2C or serial are not affected.

For each argument, set to 0 to drive low and 1 to drive high.

Parameters

io0 (int) – IO0 output value.
io1 (int) – IO1 output value.
io2 (int) – IO2 output value.
io3 (int) – IO3 output value.

get_pins()[source]¶

Get the current state of all digital IO pins.

Returns: List containing the current state of the four digital IO pins (0 = low, 1 = high).
Return type: list of int

get_ad(pin)[source]¶

Get a ADC sample from the specified analogue input pin.

This uses a 10-bit ADC, so the result is between 0-1023 for the voltage swing between VSS and VCC.

Parameters: pin (int) – Input pin to sample.
Returns: Sample value returned by the ADC (0-1023).
Return type: int

usb_iss.serial_ module¶

class usb_iss.serial_.Serial(drv)[source]¶

Bases: object

Use the USB_ISS device to perform Serial UART accesses.

Example

from usb_iss import UsbIss

# Configure Serial mode

iss = UsbIss()
iss.open("COM3")
iss.setup_serial()

# Write and read some data

iss.serial.transmit([0x48, 0x65, 0x6c, 0x6c, 0x6f]);
iss.serial.transmit_string("Hello!")
data = iss.serial.receive()

print(data)
# [72, 105]

transmit(data)[source]¶

Transmit data over the Serial UART interface.

Parameters: data (list of int) – List of bytes to transmit.

transmit_string(string, encoding='utf-8')[source]¶

Transmit a string over the Serial UART interface.

Parameters

string (str) – String to transmit.
encoding (str) – Encoding of the string.

receive(timeout_ms=100)[source]¶

Receive data over the Serial UART interface. Returns once no data is received for timeout_ms.

Parameters: timeout_ms (int) – Returns once no data is received for this period.
Returns: List of bytes received.
Return type: list of int

receive_string(timeout_ms=100, encoding='utf-8')[source]¶

Receive a string over the Serial UART interface. Returns once no data is received for timeout_ms.

Parameters

timeout_ms (int) – Returns once no data is received for this period.
encoding (str) – Encoding of the string.

Returns

String received.

Return type

string

get_rx_count()[source]¶

Return the number of bytes in the receive buffer.

Returns: Number of bytes in the receive buffer.
Return type: int

get_tx_count()[source]¶

Return the number of bytes in the transmit buffer.

Returns: Number of bytes in the transmit buffer.
Return type: int

usb_iss.spi module¶

class usb_iss.spi.SPI(drv)[source]¶

Bases: object

Use the USB_ISS device to perform SPI accesses.

Example

from usb_iss import UsbIss

# Configure SPI mode

iss = UsbIss()
iss.open("COM3")
iss.setup_spi()

# Write and read some data in a single transfer

data = iss.spi.transfer([0, 1, 2]);

print(data)
# [4, 5, 6]

transfer(write_data)[source]¶

Perform an SPI transfer.

Parameters: write_data (list of int) – List of bytes to write to the device during the transfer.
Returns: List of bytes read from the device during the transfer.
Return type: list of int

usb_iss.defs module¶

Definitions from http://www.robot-electronics.co.uk/htm/usb_iss_tech.htm.

class usb_iss.defs.Command[source]¶

Bases: enum.Enum

Command code sent as the first byte.

I2C_SGL = 83¶

I2C_AD0 = 84¶

I2C_AD1 = 85¶

I2C_AD2 = 86¶

I2C_DIRECT = 87¶

I2C_TEST = 88¶

USB_ISS = 90¶

SPI = 97¶

SERIAL = 98¶

SET_PINS = 99¶

GET_PINS = 100¶

GET_AD = 101¶

class usb_iss.defs.SubCommand[source]¶

Bases: enum.Enum

Internal subcommand used with Command.USB_ISS.

ISS_VERSION = 1¶

ISS_MODE = 2¶

GET_SER_NUM = 3¶

class usb_iss.defs.Mode[source]¶

Bases: enum.Enum

USB-ISS module operating modes.

IO_MODE = 0¶

IO_CHANGE = 16¶

I2C_S_20KHZ = 32¶

I2C_S_50KHZ = 48¶

I2C_S_100KHZ = 64¶

I2C_S_400KHZ = 80¶

I2C_H_100KHZ = 96¶

I2C_H_400KHZ = 112¶

I2C_H_1000KHZ = 128¶

SPI_MODE = 144¶

SERIAL = 1¶

SERIAL_I2C_S_20KHZ = 33¶

SERIAL_I2C_S_50KHZ = 49¶

SERIAL_I2C_S_100KHZ = 65¶

SERIAL_I2C_S_400KHZ = 81¶

SERIAL_I2C_H_100KHZ = 97¶

SERIAL_I2C_H_400KHZ = 113¶

SERIAL_I2C_H_1000KHZ = 129¶

class usb_iss.defs.IOType[source]¶

Bases: enum.Enum

IO configuration for a single pin.

OUTPUT_LOW = 0¶

OUTPUT_HIGH = 1¶

DIGITAL_INPUT = 2¶

ANALOGUE_INPUT = 3¶

class usb_iss.defs.SPIMode[source]¶

Bases: enum.Enum

SPI clock phase setting.

TX_ACTIVE_TO_IDLE_IDLE_LOW = 144¶

TX_ACTIVE_TO_IDLE_IDLE_HIGH = 145¶

TX_IDLE_TO_ACTIVE_IDLE_LOW = 146¶

TX_IDLE_TO_ACTIVE_IDLE_HIGH = 147¶

class usb_iss.defs.I2CDirect[source]¶

Bases: enum.Enum

I2C_DIRECT commands.

START = 1¶

RESTART = 2¶

STOP = 3¶

NACK = 4¶

READ1 = 32¶

READ2 = 33¶

READ3 = 34¶

READ4 = 35¶

READ5 = 36¶

READ6 = 37¶

READ7 = 38¶

READ8 = 39¶

READ9 = 40¶

READ10 = 41¶

READ11 = 42¶

READ12 = 43¶

READ13 = 44¶

READ14 = 45¶

READ15 = 46¶

READ16 = 47¶

WRITE1 = 48¶

WRITE2 = 49¶

WRITE3 = 50¶

WRITE4 = 51¶

WRITE5 = 52¶

WRITE6 = 53¶

WRITE7 = 54¶

WRITE8 = 55¶

WRITE9 = 56¶

WRITE10 = 57¶

WRITE11 = 58¶

WRITE12 = 59¶

WRITE13 = 60¶

WRITE14 = 61¶

WRITE15 = 62¶

WRITE16 = 63¶

class usb_iss.defs.ResponseCode[source]¶

Bases: enum.Enum

First byte of a response. Note: For I2C: NACK = 0x00, ACK = Non-zero.

NACK = 0¶

ACK = 255¶

class usb_iss.defs.ModeError[source]¶

Bases: enum.Enum

Error codes for the mode setting commands (second byte of the response).

UNKNOWN_COMMAND = 5¶

INTERNAL_ERROR_1 = 6¶

INTERNAL_ERROR_2 = 7¶

class usb_iss.defs.I2CDirectError[source]¶

Bases: enum.Enum

Error codes for the I2C_DIRECT command (second byte of the response).

DEVICE_ERROR = 1¶

BUFFER_OVERFLOW = 2¶

BUFFER_UNDERFLOW = 3¶

UNKNOWN_COMMAND = 4¶

usb_iss.exceptions module¶

exception usb_iss.exceptions.UsbIssError[source]¶

Bases: Exception

Raised when an error condition is detected by the usb_iss library.

Contributing¶

Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

You can contribute in many ways:

Types of Contributions¶

Report Bugs¶

Report bugs at https://github.com/sneakypete81/usb_iss/issues.

If you are reporting a bug, please include:

Your operating system name and version.
Any details about your local setup that might be helpful in troubleshooting.
Detailed steps to reproduce the bug.

Fix Bugs¶

Look through the GitHub issues for bugs. Anything tagged with “bug” and “help wanted” is open to whoever wants to implement it.

Implement Features¶

Look through the GitHub issues for features. Anything tagged with “enhancement” and “help wanted” is open to whoever wants to implement it.

Write Documentation¶

The USB-ISS Python Library could always use more documentation, whether as part of the official USB-ISS Python Library docs, in docstrings, or even on the web in blog posts, articles, and such.

Submit Feedback¶

The best way to send feedback is to file an issue at https://github.com/sneakypete81/usb_iss/issues.

If you are proposing a feature:

Explain in detail how it would work.
Keep the scope as narrow as possible, to make it easier to implement.
Remember that this is a volunteer-driven project, and that contributions are welcome :)

Get Started!¶

Ready to contribute? Here’s how to set up usb_iss for local development.

Fork the usb_iss repo on GitHub.

Clone your fork locally:

$ git clone git@github.com:your_name_here/usb_iss.git
$ cd usb_iss

Install your local clone (plus developer dependencies) into a virtualenv and activate it:
```
$ pip install virtualenv
$ make develop
$ . .venv/bin/activate
```
Create a branch for local development:
```
$ git checkout -b name-of-your-bugfix-or-feature
```
Now you can make your changes locally.
When you’re done making changes, check that your changes pass flake8 and the tests, including testing other Python versions with tox:
```
$ make test-all
```

Commit your changes and push your branch to GitHub:

$ git add .
$ git commit -m "Your detailed description of your changes."
$ git push origin name-of-your-bugfix-or-feature

Submit a pull request through the GitHub website.

Pull Request Guidelines¶

Before you submit a pull request, check that it meets these guidelines:

The pull request should include tests.
If the pull request adds functionality, the docs should be updated. Put your new functionality into a function with a docstring.
The pull request should work for Python 3.5 and later. Check https://travis-ci.org/sneakypete81/usb_iss/pull_requests and make sure that the tests pass for all supported Python versions.

Tips¶

To run the tests in the default python environment quickly:

$ make test

Deploying¶

A reminder for the maintainers on how to deploy:

$ # Update CHANGELOG.rst
$ bumpversion [major|minor|patch]
$ git push
$ git push --tags

Travis will then deploy to PyPI if tests pass.

Changelog¶

2.0.1 (2021-01-21)¶

Add serial+I2C operating modes to read_iss_mode()

2.0.0 (2019-11-04)¶

BREAKING CHANGE: Use 7-bit I2C device addresses

1.0.0 (2019-10-16)¶

BREAKING CHANGE: Remember the previous IO state in the setup_* methods (thanks SamP20)
BREAKING CHANGE: Improve the serial mode API
Add verbose logging option

0.3.1 (2018-07-02)¶

Fix Python2 serial interface

0.3.0 (2018-05-28)¶

Add SPI support
Add Serial UART support
Improve test coverage

0.2.4 (2018-05-23)¶

Add SPI, Serial and IO setup methods

0.2.3 (2018-05-22)¶

Fix and test Travis PyPI auto-deploy

0.2.0 (2018-05-21)¶

Generate documentation
Add dummy driver option for test purposes
Configure I/O as input by default
Add i2c.read/write aliases for read_ad1/write_ad1
Update setup_i2c to split out clk_khz and use_i2c_hardware parameters

0.1.0 (2018-04-19)¶

Initial release