I am currently evaluating a CFA635 for integration in my custom system. From capturing traces with a USB bus analyzer when the CFA635 is connected to a PC, I can see the initialization sequence and the transactions that occur to run a command from the Windows demo/test program to the CFA635.
The USB transaction sequence for running a command matches what is described in the documentation. For example, I see the command/response packets when I write to the LCD from the test program. I do however see the device respond with a 2-byte packet every 15 msec rather than just continuously NAK. After several of these 2-byte packets, the actual command response is sent. What are these 2-byte interim packets?
I cannot find documentation for some of the USB transactions that I see during initialization. I see the standard USB setup get descriptor requests and the device response appropriately, but then I see several non-standard setup requests sent to the device. Can someone point me to some documentation for these non-standard setup requests? Are they custom to the CFA6xx or are they part of some "standard" USB-serial protocol? Since my system is running a custom OS, I cannot use the Windows or Linux driver directly.
Thanks.
The USB transaction sequence for running a command matches what is described in the documentation. For example, I see the command/response packets when I write to the LCD from the test program. I do however see the device respond with a 2-byte packet every 15 msec rather than just continuously NAK. After several of these 2-byte packets, the actual command response is sent. What are these 2-byte interim packets?
I cannot find documentation for some of the USB transactions that I see during initialization. I see the standard USB setup get descriptor requests and the device response appropriately, but then I see several non-standard setup requests sent to the device. Can someone point me to some documentation for these non-standard setup requests? Are they custom to the CFA6xx or are they part of some "standard" USB-serial protocol? Since my system is running a custom OS, I cannot use the Windows or Linux driver directly.
Thanks.
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