8-bit MicrocontrollersのトピックJM series as virtual com port

JM series as virtual com port

Juls — Mon, 23 Aug 2010 07:20:51 GMT

I need a little cpu with some flash

and usb too

two choice open to me

a simple cpu with a sci and a ftdi chip for the usb

or a JM serie JM60 or a coldfire jm serie (I got a demoJM to test things up)

Is at possible to make a virtual com port from the usb controller on the cpu

I read something about cdc device but not sure its what im looking for

is there any example or application note about this?

Thanks guys

Re: JM series as virtual com port

rocco — Mon, 23 Aug 2010 10:56:15 GMT

Hi Juls,

It really depends what you intend to do with it. A CDC device is typically used for modems, and would be the obvious interface if you're building a modem or similar device. If you need USB simply to re-flash firmware, it might not be appropriate.

I have hooked the FTDI FT232RL chip to the SCI, and I doubt anything else is easier to implement. But there are sacrifices with that approach.

With the FTDI approach, you can configure the FTDI chip to act as a virtual comm-port, or configure it as a custom device. You have no firmware to write if you already have SCI firmware (as I did). With a virtual comm-port, you also have no host driver to write. If you need to write host software, it is simpler if it is written for a comm-port.

But the final interface would not be as flexible as with a native USB device on a JM processor. It also would not be as fast, as the fastest SCIs are limited to 1 mega-baud. But then again, there is the USB firmware to write and maintain, which is far from trivial.

In my case, none of the JM devices had the peripherals my application needed, so FTDI was the obvious answer.

Just a few of the things to consider.

Re: JM series as virtual com port

Juls — Mon, 23 Aug 2010 18:46:03 GMT

The goal is to make the JM act like the ft232R chip configured as VCP

so windows see it as a com port and no driver must be write

Re: JM series as virtual com port

DSchwertb — Tue, 24 Aug 2010 04:42:01 GMT

Hi Juls,

the documentation for the JM is spread over many application notes and other files and so it's difficult to find a good starting point.

The CMX USB stack that you can download from the Freescale web site includes a demo "cdc-terminal-demo".

(Just use the keyword search to look for "S08JM_USB_Lite_CMX".)

Have a look at that. I think that's a good starting point for you.

Alternatively, have a look at http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=USBJM_TRAINING for an approach which does not use CDC.

Regards,

Dietmar

Re: JM series as virtual com port

Juls — Tue, 24 Aug 2010 20:38:04 GMT

I just tried

C:\CMXUSB_LITE_V1\usb-peripheral\projects\CodeWarrior-6.x\mcf51xx\cdc-demo

using MCF51J128 on DEMOJM

And it work as expected

will require a few modification to my setup

and will probably work on 9s08 too

Thanks all