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Martin Hepperle · 07-16-2018, 02:24 PM

(07-16-2018 01:39 PM)ijabbott Wrote: ...
Even for USB serial devices, there are quite a few different types (FTDI, Prolific, Silicon Labs, WInChipHead, to name a few) each with their own protocols for embedding data, line control and status information into USB packets. There are some devices that use standard USB serial device protocols such as USB CDC to appear as some sort of "modem", but the common ones I listed don't. It all gets very complicated!

My 5 cents:

Let's look at the success of Arduino and similar platforms which are also used in education. This ecosystem provides a huge number of sensors and devices.
Projects typically consist of the microcontroller board which is combined with one or more external sensors and output devices.
In the majority of projects the following types of Interfaces are used:

serial at 5V or 3.3 V level ( not true RS232) for e.g. GPS sensors or links to other computers,
the I2C bus (TWI) to sensors and displays,
only a few use limited USB CDC capabilities to mimic keyboards and mice.

A "simple" USB to TTL converter cable and associated read/write commands would enable many applications e.g. in the education world. Optionally one could also think about combining this with an I2C Interface (Tony Duell built one many years ago for the HP-48). But this would already become complex.
Such an simple serial interface could be tailored to be connected to an Arduino or similar which could then translate and forward commands (sent via serial) to e.g. I2C or other systems. A small library could be created to encourage people to tinker, using the Prime as a controller, doing calculations and displaying results. This would replace keyboard and display on the Arduino.

The old Fourier sensor thing was probably o.k., but expensive. Today it seems to be outdated and not really suitable for tinkering by kids. Maybe something to discuss with physics teachers etc. I have no idea whether this is really a market.

As this interface would contain a single USB chip (e.g. Prolific or whatever), the firmware in the Prime would only need to be adapted to talk to this chip. Not a generic USB interface with drivers for lots of different USB chips.

- rant mode on -
In general USB seems to be rather volatile technology - it has burnt many people due to e.g. Windows driver policy "arbitrary" dropping support for certain USB chips, manufacturers dropping support for older USB devices. How many different USB cables do you own (A,B,C, mini, micro, power, data, ...)?
The plain old serial (TTL or RS232) interfaces are independent of such "modern technology" and astonishingly resilient. Many POS printers still use RS232 and talk ESC/p - surviving since the 1980s.
- rant mode off -

Martin