Drive the MCP2200 with python

MCP2200 is the Microchip USB-Serial transceiver. Datasheet

The USB link is also used to configure the device, and, as a bonus, to easily manage some GPIO and EEPROM on the device.

When connected to a computer, it creates 2 new USB devices

• A USB CDC that's the actual virtual serial port any tool will use to communicate.
• A USB HID, that can be used to personalize and configure the chip.

The MCP2200 is delivered along with a user interface that helps easily configuring it. BUT... it's pure Windows !!

Thanksfully, Microchip delivers this document as well : The fully documented HID protocol

This project implements the microchip specifications at 3 levels :

• The graphical configuration tool
• The USB HID specification
• The API as described in the component's datasheet

Install

git clone https://github.com/cdtx/mcp2200.git
cd mcp2200
pip install -r requirements.txt
python setup install

GUI

Example at USB HID level

from cdtx.mcp2200.device import MCP2200Device

try:
    dev = mcp2200Device(autoConnect=True)
except:
    sys.exit('Cannot connect the device')

try:
    # Set GPIO 0 as output and set it
    config = dev.read_all()
    # Reset bit0 of IO_bmap
    config['IO_bmap'] &= 0xFE
    dev.configure(**config)
    dev.set_clear_outputs(Set_bmap=0x01, Clear_bmap=0x00)
finally:
    mcp2200.disconnects()

Example at API level

from cdtx.mcp2200.api import SimpleIOClass

# Init class and connect device
dev = SimpleIOClass()
dev.InitMCP2200(0x04d8, 0x00df)
assert dev.GetNoOfDevices() == 1

# Set GPIO 0 as output and set it
dev.SelectDevice(0)
assert dev.IsConnected() == True
# Set all pins as outputs
dev.ConfigureIO(0x00)
dev.SetPin(0)
assert dev.ReadPinValue(0) == 1

Problem with permissions ?

1. Quick and dirty solution is to install and run as root

2. Prefer allowing current user to manage USB devices

Add the following rule to file /etc/udev/rules.d/50-myrules.rules (create if necessary)
```
ATTRS{idVendor}=="04d8", ATTRS{idProduct}=="00df", GROUP:="plugdev", MODE="0660"
```

The current user must belong to the __plugdev__ group
```
sudo usermode -a -G plugdev ${USER}
```

[Source](https://askubuntu.com/questions/112568/how-do-i-allow-a-non-default-user-to-use-serial-device-ttyusb0)