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Author Topic: FT900 D2XX and CDC ACM Bridge  (Read 1399 times)

Pranash

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FT900 D2XX and CDC ACM Bridge
« on: January 13, 2021, 02:53:40 PM »

Hello All,

I'm building a USB bridge to UART and CAN, I used D2XX for UARTs and for CAN I need to use CDC ACM, as FT900 supports only 3 D2XX interfaces and I need 4 interfaces in total.
Can anybody help me to understand how to configure D2XX and CDC ACM in the same program to show 4 virtual COM ports?

Thank you.
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Re: FT900 D2XX and CDC ACM Bridge
« Reply #1 on: January 14, 2021, 04:19:05 PM »

Hello,

Yes the number of D2xx interfaces is limited to 3 on FT900.
There are 7 D2xx interfaces on our FT930 products, but they have no CAN interfaces unfortunately.

So what you need to do is to concatenate some code. We have a few examples in AN_360 FT9xx Example Applications to help you:

D2XX Example 1
D2XX Example UART Bridge
USBD Example CDCACM

The other alternative is to create 4 x CDCACM interfaces and don't use the D2XX interfaces.

Full source code the for examples is provided with the FT9xx Toolchain:

C:\Users\Username\Documents\Bridgetek\FT9xx\2.5.0\Examples

It is possible that other BRT community users have done something similar to help you.

Best Regards,
BRT Community
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Pranash

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Re: FT900 D2XX and CDC ACM Bridge
« Reply #2 on: January 14, 2021, 04:52:52 PM »

So what you need to do is to concatenate some code. We have a few examples in AN_360 FT9xx Example Applications to help you:

D2XX Example 1
D2XX Example UART Bridge
USBD Example CDCACM

I tried to do this, but for some reason only CDCACM port is visible and D2XX ports aren't. That's why I came here to see if anyone has any better idea to do this.

The other alternative is to create 4 x CDCACM interfaces and don't use the D2XX interfaces.

Full source code the for examples is provided with the FT9xx Toolchain:

C:\Users\Username\Documents\Bridgetek\FT9xx\2.5.0\Examples

For this, how can manage the endpoints, as there are only 6 data endpoints are available and all are unidirectional. So, are you suggesting to share the endpoints between multiple CDCACM interfaces? I'm not sure if the buffer will be sufficient in that case, and I don't think I can go to high power mode.
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Re: FT900 D2XX and CDC ACM Bridge
« Reply #3 on: January 18, 2021, 04:35:34 PM »

Hello,

There are only 7 IN/OUT endpoints for the USB Device controller on FT900.

If you are using all three D2XX interfaces on FT900, there is only one IN/OUT endpoint left.
So you cannot add an additional CDC ACM device as that would need more than the number of endpoints available for the data and communication interface.

Maybe you would like to consolidate your design to use say 2 x D2xx interfaces and 1 x CDC interface.

Best Regards,
BRT Community
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Pranash

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Re: FT900 D2XX and CDC ACM Bridge
« Reply #4 on: January 18, 2021, 05:44:44 PM »

But that won't solve the problem, as I want 4 interfaces in total, are you saying that it's impossible with FT900?
Also, in your earlier reply you suggested that I can configure 4 x CDCACM interfaces, can you help me in understanding how can I do that?

Thanks,
Pranash
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Re: FT900 D2XX and CDC ACM Bridge
« Reply #5 on: January 20, 2021, 04:44:14 PM »

Hello,

Yes this is impossible with the FT900 due to the number of USB Device endpoints available.

The previous post was written before checking the number of endpoints available.

Best Regards,
BRT Community
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