View Full Version : USB Host for Propeller Platform

11-17-2010, 05:48 PM
Here's a little board I'm having made right now.
It's based on the MAX3421E.

It plugs right into the Propeller platform and uses a 4-pin SPI interface to communicate. There are also 2 optional pins for interrupts.

The board also has 8 general purpose inputs and 8 general purpose outputs.

The MAX3421E can also act as a USB peripheral controller, which is why there are 2 USB connectors.... The little one is when you want to act as a peripheral, the big one is to host.

Assuming it works, it should allow a lot of USB devices to be connected to the Prop....

11-17-2010, 06:31 PM
It should cost more or less like a propeller and has 8I and 8 Os... very neat !

11-18-2010, 02:18 PM
Chip cost is a problem... But, there's lots of code out there for interfacing this chip with all types of USB devices. What I like about this chip is that it is very small and simple to use.

11-18-2010, 03:40 PM
Actually, I'm starting to think I should use the Vinculum II chip instead. It's cheaper and has 2 host interfaces, so it could do keyboard and mouse...

Nick McClick
11-18-2010, 05:37 PM
I've been looking at the Vinculum II - there's also a good article series on it in Nuts & Volts - looks like a really cool chip and the pricing is better than the FT232R. It does require more external discretes, though.

11-18-2010, 10:55 PM
It appears that using the Vinculum2 to replace the FT232R would require custom firmware. But, they now give out (free?) tools to build custom firmware, so that should be doable.

The strange thing is that you need a FT232R connected to the Vinculum2 to do development. (That's not completely true because you can use the serial port to upload firmware).

I think I'd rather stick with the MAX chip, but looking at $12 for 2 USB ports verses $4 with Vinculum2 makes me like that way better.

Nick McClick
11-19-2010, 12:23 AM
That looked like the other downside for the Vinculum 2. I wonder if there's a way to program it with a Prop Plug...

11-19-2010, 12:50 AM
Don't think so... You need access to a couple pins that aren't brought out...

For people like me that use the bigger, pinned version, you could solder wires to the pins you need in a pinch....

11-19-2010, 12:57 AM
One thing I want to try is fitting a VNC2-48LQFP to the existing parallax datalogger, which in my opinion is very well priced at $35. I've ordered both bits, but was secretly hoping someone else eg Parallax would try it first
http://www.parallax.com/tabid/768/List/0/ProductID/434/Default.asp (http://www.parallax.com/tabid/768/List/0/ProductID/434/Default.aspx)

I believe the VNC2-48 is pin compatible with VNC1, but yes new software may be required, but surely VNC1 emulation would be high on FTDI's priority list

11-19-2010, 01:40 AM
I believe there is firmware available that would make the 48 pin chip behave exactly like it's predecessor.

11-19-2010, 01:41 AM
One interesting new feature is the SPI host. Somebody'd have to write the code, but that should allow SD card access from the VNC2...

Wait a minute... I just thought of a great idea...

Ok, I was thinking about making a board that plugged into the SD card socket, but the Prop Platform makes that not such a good idea since you already have access to the SD card's pins...

After thinking about this some more, the only reason I'm leaning toward the VNC2 over the MAX chip is the presumed ability to talk to a mouse and a keyboard using only a 4 pin SPI bus.

11-19-2010, 12:51 PM
Ok, now I'm flip-flopping back the the MAX3421E. The VNC2 may be a better fit for Prop1, but I'm already thinking about Prop2. The Prop2 will supposedly be able to do the job of the MAX3421E, but it will still need similar SPIN or assembly code to interface with various devices. So, any code that is written for this chip will carry over to Prop2...

Oldbitcollector (Jeff)
12-01-2010, 05:12 PM
Not sure how I missed this!

Can we get an update on this project? This is big news indeed.


12-01-2010, 10:59 PM
OBC, No news yet... I have the board and the Maxim chip, but haven't tried it yet (I'm fixated on putting a Prop in my Coby keychain photoviewer).

09-24-2011, 08:04 AM
Hi Rayman.

I made USB_Host curcuit(same as MAXIM's sample curcuirt) with MAX3421E.
I translated MAXIM's code to PropForth.
Prop can read mouse's Descriptor.
But in case of FullSpeed Device(USB memory), prop can't read it.
MAX3421E return hrJERR after sending first setup-token to USB-device.
Do you know this trouble?

09-24-2011, 12:39 PM
I'm embarrased to say that I never did anything with my poor circuit... I decided it would take a huge investment of time to make it work. And then, that chip costs so much, I didn't think anybody else would use it...

BTW: I'm now looking at Vinculum II chips to do the same thing. They are half the price and have 2 USB host controllers. But, this will also take a huge effort to get going (so it may not happen).

11-21-2012, 09:45 PM
Someone is asking offline about this and so I'm posting the ExpressPCB files for this project here in case anybody wants to pursue it...