Interface for communicating with various densitometers via the USB port

[dkonigsberg]

This feature is an internal interface layer that is primarily needed to support #5 .

Various densitometers have mechanisms for interfacing with a computer to ease data input for processing measurements. They primarily do this via a serial-like interface. To make step-wedge-based paper profiles a lot less tedious to create, we should support this whenever possible.

For starters, using the USB port on the Printalyzer, it should be possible to directly capture readings from the following two densitometers:

• Heiland TRD-2 /w USB option
  • Presents itself as a USB serial port
  • Has a fairly simple protocol where it streams readings
• X-Rite 810TR
  • Has an RS-232 serial port on the back
  • Should be able to use a common USB-to-Serial adapter to interface with this (not sure if that code can be universal, or if it'll need specific support for specific chipsets)
  • Has a more sophisticated interface, where we can control the device's modes and take readings

[dkonigsberg]

The actual serial interfaces for both of these densitometers are almost trivial to handle. The real challenge appears to be that USB serial interfaces are not USB CDC class devices with existing support, and tend to use a vendor-specific device class. So, a prerequisite to adding this feature is implementing drivers for relevant popular USB serial chips.

As both the TRD-2 and my spare USB-to-Serial adapters use the FTDI FT232R chip, it probably makes sense to focus on support for that as a first step.

[dkonigsberg]

USB<->Serial adapter support added by: 8f39fe3e4f696fdabf6a5ff56dc742bcab0c58be c6ba9401a1326361b2ecbd35e770a2da240a4940 c92295699a10020d62b87e4733b849f8173a264a 894a3f0dc69531b906cc4c6330b4b1fb60d6c766 59690e0fd5dfe73d8c142b0391324d747fe70d15 1a5529376789b01d827b437e531bbedd0742e59b cf627fea2c7d3e3f12102f26b0492aa7e92eeea4 a864b34d06475cab1e2a191ce63983a1a6d96d49