USB HID - is it possible with Parallax chips?
OakGraphics
Posts: 202
I was reading the article in Circuit Celler's August 2006 issue (page 29) called "USB Volume Control" where the author made a volume controller for windows based on an max3420e chip,·an Atmel AVR·ATtiny13 microcontroller and a rotery dial.· This seemed very interesting to me as it's close to some things I would like to do, but was hoping to get more of an experiment thing together to learn USB Human Interface Controlling.· The key was the max3420e chip could be controlled via SPI, or could be controlled via a 'bit-banged' SPI.· Also - the ATtiny13 had about 512 words to program.· Is there a comparible solution using parallax chips? (i.e. bs1 (doubtful - not enough program space I figure), BS2, SX, or Propeller)·· I currently have BS1, BS2, and some SX52 development boards that I haven't started playing with, but propeller is very enticing.·
Also - if not the max3420e - then what would be best for this?· I know Parallax has some usb to serial things but I don't think that it is capable of HID - and that would be key I think.
Just looking for a direction to start that won't be impossible from the start. :-)
·
Also - if not the max3420e - then what would be best for this?· I know Parallax has some usb to serial things but I don't think that it is capable of HID - and that would be key I think.
Just looking for a direction to start that won't be impossible from the start. :-)
·
Comments
The USB to serial adapters are not HID devices. They can only provide a serial UART.
Also, The Electronic signals are NRZI, and you cannot cleanly toggle pins against each other (to 'bit bang')·to get a clean enough eye pattern...especially at those speeds.
The best route is to incorporate the FTDI Chip into your design. It contains the low-level USB Protocol stack and is USB Compliant.· I know that's not what you want to hear, but USB is something that generally needs to get implemented into the Silicon.
http://www.parallax.com/detail.asp?product_id=604-00043
Other than that, there are a few PIC chips that have the USB Stack, but I don't care that much for PICs.
...The bad part about a chip with a USB Stack is that you will have to program your device, Class, Interface, and Configuration Descriptors...you will also have to develop your own driver API for the PC.
Unless you hire a full-time USB Development Engineer, you are better off with the drop-in module from FTDI.
Post Edited (Steel) : 9/13/2006 10:15:08 PM GMT
I am also looking for a good primer on HID - because I want to not only have inputs on the controller, but also outputs - like LED bar-graph (like for the volume percentage), and pwm control, as well as something more in the ballpark of 3 rotery digital encoders for input.
Keep in mind that the Stamp program EEPROM can also hold data (DATA/READ/WRITE commands). On the BS2, there's not a lot, but, with the other ones, particularly the BS2pe, there's a lot available.