Re: An interesting chip for USB applications

From: Marko Mäkelä (
Date: 2006-10-08 16:12:43

Hi Wolfgang,

On Sat, Oct 07, 2006 at 11:38:44PM +0200, Wolfgang Moser wrote:
> Hello Marko,
> Marko Mäkelä schrieb:
> >A friend of mine recently told me about the MAX3421E from Maxim
> ><>.
> >He ordered some samples, but the estimated delivery time is in March 
> >2007.
> >Also, there are virtually no programming examples yet.
> >
> >The chip implements a USB interface, and it is controlled via SPI bus.
> >It seems to support enough primitives to implement any USB protocol.
> to me this chip looks like just another USB to any other
> general availability serial bus. Beside RS232 (ft232bm or
> pl2302) or 8-bit parallel fifo (ft245) a SPI this time.

Those chips you mention use their own proprietary USB protocols and
need special drivers on the PC.  The MAX3421E (as well as its precursor
MAX3420E) allow you to define your own protocol over the USB by
controlling the chip over the SPI bus.  I would guess that the two most
popular protocol classes to implement would be usb-hid (human interface
device, i.e., keyboards, mice, joysticks, or low-bandwidth sensors) and
usb-storage (block device).  Both classes are natively supported by
operating systems.

> At first there's the Cypress EZ-USB series with the FX
> and FX2 µCs.

The Keyspan usb-to-serial converters have been built using that chip.
Do you know if it supports USB 2.0 or USB-on-the-go? Is it available
in small quantities?

> Secondly there are Microchips PICs with builtin USB cores
> I heard about some Cons regarding the USB implementation,
> but that may be bad rumors only from people not having
> fully understood the specs or the concepts.

That would be understandable, as USB is a very complex standard.

> The dual chip solutions always have one clear
> advantage over the integrated USB chips: You don't
> need any USB programming knowledge, when the chip
> manufacturer delivers proper USV drivers as well.

I think that you are slightly mistaken about the Maxim chip.
It requires quite a bit of USB programming knowledge,
although it seems to handle some low-level stuff, such as
retransmissions.  I do not have any experience in low-level
USB programming yet, though.


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