USB Interface, using FT232R

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hm_fa_da

Joined: 16 Sep 2003
Posts: 193
Helped: 6

15 Jul 2007 10:09 ft232r interface

Hi ,

I have bought FT232 and going to use it in my project, but i have some questions ,
i want to have something about 10 Mb/s so i should use full speed mode which is 12 Mb/s ,
but i have read in FT232R datasheet that :
"Data transfer rates from 300 baud to 3 Megabaud (RS422 / RS485 and at TTL levels) and 300 baud to 1 Megabaud (RS232)."

it means the maximum speed is 3Mb/s ?
if yes , what should i do to have more speed ... , i want to connect the chip directly to my MCU .

i have read in PCIUSBD12 ( Philips ) USB interface chip that it supports :
"High-speed (2 MB/s) parallel interface to any external microcontroller or
microprocessor"

i think i can use this but if there is other ways and easy to use chips , i'll be glad to know .

Thanks & Regards.

foxabilo

Joined: 16 Jul 2007
Posts: 67
Helped: 12
Location: Derby, England

16 Jul 2007 22:19 ft232r hid

Hello,

The term "Full Speed" in USB terms is very confusing, it usually refers to compatibility with USB2.0 host controllers. A USB2.0 Real full speed device is capable of 480Mbs in theory, so 12 is a little misleading.

Also, the 12Mb/s rate stated is for Block Transfer mode only, the slower speeds you are seeing are being quoted as RS232 or RS232alike drivers which usually don't go over 1Mb/s but can sometimes go higher, the RS232 driver is installed on the PC and simulated a com port to any application needing it, the slower speed is due to the overheads in the transfer. i.e encoding RTS, CTS etc into each data packet sent and simple compatibility reasons, no real RS232 device went much over 1Mb/s most not even over 115,000 baud so most applications only use this range.

So to answer your question you will need to look at using USB Block transfer mode and not any of the much simpler HID and RS232 emulator drivers, if you use CCS C there are examples for simple block transfer mode in the SCOPE.C but I am sure examples exist for other compilers/micro controllers
Fox

hm_fa_da

Joined: 16 Sep 2003
Posts: 193
Helped: 6

17 Jul 2007 8:28 scope ft232r

Quote:

The term "Full Speed" in USB terms is very confusing, it usually refers to compatibility with USB2.0 host controllers. A USB2.0 Real full speed device is capable of 480Mbs in theory, so 12 is a little misleading.

480 Mb/s is named high speed , 12 Mb/s full speed in both USB 1.1 and USB 2.

however thanks for your answer , but do you know any chip which handles these processes and i be able to have something about 8Mb/s data transfer between my board and PC ?

foxabilo

Joined: 16 Jul 2007
Posts: 67
Helped: 12
Location: Derby, England

17 Jul 2007 9:00 pic usb interface with ft232rl

Thanks for the correction Smile

, any of the USB chips i.e PIC18F4550 etc will do 2-5Mps if you use the "bulk mode transfer" (last post I said it was block mode, my bad). There are many examples of PIC block mode available too, http://forum.microchip.com/printable.aspx?m=94120 but the fastest speed as I mentioned is around the 5Mb/s rate and the slowest was ~1.4Mb/s.

I'll hazard a guess that you are transferring video data if you require that bandwidth. The problem with the PIC range is that the chip is clocked at 48Mhz and each instruction needs 4 clocks so your down to 12Mips , and as you know, you need to loop to send data so you have at least 1 instruction + 2 instructions for the jump in the loop dividing the value of 12 by 3 already so your now down to 4Mb/s.

I have successfully overclocked the 4550 to run at 96Mhz giving 24 Mips but that's not really a proper solution unless this is a one off project for yourself, and even then it would only just scrape in at 8Mb/s.

I dont have experience with AVR's but they do at least run Clock to instruction 1:1 for most things so they end up being faster, basicaly to be idea you require about 36 Mips to be safe unless you can use some form of DMA transfer but that is going out of my knowledge range

hm_fa_da

Joined: 16 Sep 2003
Posts: 193
Helped: 6

17 Jul 2007 11:38 ft232r using

Thanks for your answer dear , i usually use AVR MCU in my projects and wont use PIC , however i may go to use FPGA too , in fact i want to use a Chip like FT232R for USB handling ... ,

if you know some chip like FT232R which supports higher speeds , i'll be thankful to know it ...

blueroomelectronics

Joined: 17 Sep 2006
Posts: 1681
Helped: 99
Location: Toronto, Canada

18 Jul 2007 17:38 interface for ft 232r

Too bad you don't like PICs some dsPICs run at 30MIPs

wek

Joined: 21 Dec 2004
Posts: 239
Helped: 26

23 Jul 2007 11:37 using ft232r

Have you had a look at the FT245's? Although still Full speed, you might be able to squeeze out slightly more off them...

JW

aa2206

Joined: 29 Jun 2007
Posts: 4

23 Jul 2007 17:53 rts cts ft232r

Although still Full speed??

hm_fa_da

Joined: 16 Sep 2003
Posts: 193
Helped: 6

23 Jul 2007 23:00 ft232r host

the problem is not being full speed or not, it is that it only gives 3M baud for data transfer ... means 3Mb/s and i need more speed ...

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segmex

Joined: 25 Oct 2006
Posts: 223
Helped: 6

24 Jul 2007 6:22 ft232r fpga

any example ???

ho83

Joined: 29 Jul 2007
Posts: 21

10 Aug 2007 9:34 ft232r interfejs

check ft245bBM , it is capable of reahing 1M Byte /s using the D2xx driver. make sure to install the driver so that your application will see the the device as usb device, and not as a vitual com.