MCU + USB

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Hi,

I don't know if there is a better group to ask about USB.

I want to create a device that will communicate with a PC via USB. I
prefer USB to RS232 because I plan to power the device from the USB
supply.

I guess I have (at least) two options:
1) I use an MCU with integrated USB interface.
2) I use any MCU, plus an FTDI FT232R (USB-UART device), or
equivalent.

Option 2 makes programming very simple (I don't need to write firmware
to manage USB), but its hardware is more expensive than that of option
1 (those FT232R's are quite expensive (2.50 GBP + taxes)).

Option 1 would allow the cheapest hardware, but coding would be
harder. And here is where I start needing your help.
- Do I need to write a new USB windows driver, to communicate with my
hardware? Are there predefined "classes" of drivers that already allow
something so simple as asynchronously sending bytes back and forth?
- If I need to write a new driver, how difficult is this?
- Does anyone know of a MCU which includes: USB (even low speed would
be ok) + ADC (8 ch x 10 bit, min) + PWM (4 ch x 8 bit, min) + flash +
ISP?

For me, the best would be to find an MCU that connects directly to the
USB bus, but including an USB-UART converter inside, so that I don't
need to write USB code, but only UART code. That would really simplify
things.

Thanks a lot,
Mochuelo

Re: MCU + USB

Quoted text here. Click to load it

You missed out the most important critera to answer your question. How
many units are you going to sell? How fast do you need to get it to the
market place? What percentage of the final unit cost does the USB costs
represent?


Re: MCU + USB

Quoted text here. Click to load it

I uyse the cypress FX series of 8051/USB devices. FX2LP..  They give you the
driver and the api. It does work. I have three products using it right now.
Not _that_ hard to get up and running but not a simple task either. I chose
not to go the FTDI route because in the end.. it would have simply been a
slow serial interface. After the initial learning curve I can now implement
USB anywhere.

I believe the cypress parts are actually cheaper than the FTDI part.

YOu can also get a little FX2 Usb development board from bitwise systems.
google it.




Re: MCU + USB

Quoted text here. Click to load it

I would gladly accept some learning curve. I do like challenges, but I
would prefer taking them with a core newer than the 8051.

Quoted text here. Click to load it

Yes, and so are some 8-bit (e.g. Freescale 908JBx) and 32-bit (e.g.
Philips LPC214x) MCUs. I specially like the LPC214x option because
those MCUs are cheap, powerful, and already include the other
peripherals I mentioned I need. If someone tells me that Philips
provides similar tools to develop the USB driver, I could go for
option 1.

Is there anything similar to http://www.jungo.com/usb_device.html but
for ARM7 LPC214x devices?

Quoted text here. Click to load it


Re: MCU + USB

Quoted text here. Click to load it
the
now.
chose
implement

4 clock/48Mhz device. Pretty quick for most things.




Re: MCU + USB
Quoted text here. Click to load it

You should also look at the ARM SAM7 CPUs from Atmel.

The USB ARM CPUs (LPC214? and SAM7) are very different from the
8051 based EZusb/FX2.  In fact, they are so different, that you
shouldn't even be considering them as alternatives for the same
application.

The ARM chips are much more powerful CPUs, but they are only
full-speed USB (12mbps) capable.  The EZusb/FX2 is high-speed
USB (480mbps), 40 times the bandwidth.  The 8051 core is not a
limitation, because the chip has integrated high speed FIFOs, and
a programable interface, so the 8051 just sets everything up, and
then gets out of the way.  The data then moves between the GPIF,
FIFOs and USB with no CPU intervention.

So if your application is very data intensive, with little need
for computing power on the client end, the EZusb/FX2 is a
good choice.

If your data bandwidth needs are more modest, but you want
some CPU horsepower, or the convenience of a high level
language, then the ARM CPUs (LPC214? or SAM7) would be
good choices.

There is an active Yahoo group for LPC2???:
http://groups.yahoo.com/group/lpc2000
Engineers from Philips participate in the group regularly.

Quoted text here. Click to load it

Don't know.  I am not a Windows guy.  My desktop is running
FreeBSD, so instead of going to jungo.com and paying $3000,
I just type "cd /usr/ports/misc/ezload; make install".


Re: MCU + USB

Quoted text here. Click to load it

Also, is it true that if I go for option 1 I need to buy a (USB)
vendor ID, and that this is expensive?



Re: MCU + USB


Quoted text here. Click to load it

NOt necessarily. I am not sure what you are doing but a Vendor ID is $1500.
Although you can run with the Cypress VID using their driver.. or you can
fake your own for in-house use.


Quoted text here. Click to load it



Re: MCU + USB
I'm using the PIC18F2455 for a USB interface. It's available in DIL,
which makes it easy for prototyping, and includes the transceivers. I'm
designing the PCB, so I won't know how easy or difficult it is until I
have the prototype hardware working.

Leon


Re: MCU + USB
Quoted text here. Click to load it

SiLabs C8051F320 have FLASH + USB, and Atmel AT89C513x series have
Flash/USB, but are light on the ADCs.
Cypress have a number of choices, with good maturity.

.. but if the F232R WILL do all you need, without development times,
you need to look at the volumes carefully to justify using something
else. ( and then, FTDI caim $1.80/10K)

-jg




Re: MCU + USB
Quoted text here. Click to load it

I should add the ST uPSD34xx series, with full speed USB,
and Maxim have an interesting SPI<->USB device, the MAX3420,
if you want serial (low pin count), but faster than FT232R.
-jg


Re: MCU + USB
On Sun, 11 Dec 2005 14:00:53 +1300, Jim Granville
Quoted text here. Click to load it

Yes, I'm having a headache about this.

Quoted text here. Click to load it

I'm curious. Where did you read that price? The WebShop at the FTDI
page sells the FT232RL for 3.83 EUR, in units, but doesn't say any
other price for larger volumes.



Re: MCU + USB
On Sun, 11 Dec 2005 12:23:17 +0100, Mochuelo

Quoted text here. Click to load it

Sorry, it does say:
US$4.5000/pc, in units.
US$3.6024/pc, for 100 pcs.


Re: MCU + USB

Quoted text here. Click to load it

Google on [FT232R price ], and near the top is
http://www.eeproductcenter.com/logic/brief/showArticle.jhtml?articleID17%4900139



Re: MCU + USB
Quoted text here. Click to load it

Lookup the "Communication device class" (or just CDC) on usb.org.   This
provides a standard way of providing a virtual COM port that is supported by
Win98 onwards.  No Windows side programming is required.

If you take a look at the SAM7X lwIP demo application in the FreeRTOS.org
download (link below) you will find some sample source code.   When you
connect the USB to Windows it registers as a normal COM port so can be
accessed just like a 232 port.

Regards,
Richard.

http://www.FreeRTOS.org




Site Timeline