Hello,
I need to design a board which should send data to a computer via USB. The data is composed of a packet of about 25/30 bytes sent every 10 ms. A software running on the PC side should receive this information and store it on a file.
I'm wondering if it's better to use an FTDI chip and make the things easy using a virtual COM port or to implement a "true" USB communication (HID?).
I'm afraid about the speed needed to receive and save the string into a file.
What do you recommend? Marco
On a sunny day (Sun, 17 Oct 2010 22:23:47 +0200) it happened Marco Trapanese wrote in :
30 bytes means 300 bits, (x 10 because 1 start -, 8 data - , and 1 stop bit added). 100 x per second makes = 30000 bps. Standard baudrates above that are 38400, 57600, or 115200. If you use 115200 Bd you should be fine with a serial to USB converter, if I did the math right.Tim
-- Deep Friar: a very philosophical monk. Website:
What makes you think that a virtual COM port with an FTDI chip is not "true" USB communication?
HID is a USB class, and makes sense if you are making a mouse or a keyboard, or something that will act like a mouse or keyboard. It certainly does not sound like that's what you are doing.
A virtual COM port (using FTDI chips, or some other kind) is almost certainly the easiest solution. You can pretend the FTDI chip is just an RS-232 driver - you connect to it with a UART, and at the other end you've got a new comms port on the computer. It works with any system (plug and play on Linux, or by installing FTDI's drivers on Windows), and you can use a whole range of baud rates up to about 3 MBaud.
FTDI chip, Then you don't need a PID and VID since its in the FTDI already.
Cheers
Il 17/10/2010 23:57, David Brown ha scritto:
The "other end". On the pc side if I use a virtual COM port I need to receive data from it. I was thinking that a custom driver that get data directly from a USB class could be faster.
You're right. I used HID to make my own joystick controller, but I saw people that use HID to exchange data.
Ok, I got it. I thank all other guys who answered me.
Marco
Il 17/10/2010 23:43, Tim Williams ha scritto:
*Very* interesting!Thanks! Marco
You can talk directly to the FTDI driver you don't have to use it as a virtual comport.
and you data rate is extremely slow for usb, a few 100 times faster shouldn't be problem even for a virtual comport
I think that is mostly to avoid the need for a driver
-Lasse
Have a look at that..
It probably make more sense to implement it as USB Mass Storage Device, with or without file system encoded. Since you are storing data as a file and the PC reading data as a file, it should be a file storage device.
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