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SuperDave
Joined: 22 May 2008
Posts: 63
Location: Madison, TN
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| USB_Put_Packet length question |
 Posted: Wed Jul 02, 2014 2:46 pm |
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Given this line
usb_put_packet(endpoint,data,length,toggle)
and
data is a 32 word array of 16 BIT integers
and
the descriptor defines a 64 BYTE endpoint.
Is length 32 or 64? |
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jeremiah
Joined: 20 Jul 2010
Posts: 1353
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| Posted: Wed Jul 02, 2014 4:56 pm |
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| In the file where the function is defined, you should see what the parameter variable types are. If the parameter for data is int8*, then the length will be in reference to an 8bit value array. If the parameter for data is int16*, then the length will in reference to a 16 bit value array |
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oxo
Joined: 13 Nov 2012
Posts: 219
Location: France
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| Re: USB_Put_Packet length question |
| Posted: Thu Jul 03, 2014 2:47 am |
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| SuperDave wrote: | Given this line
usb_put_packet(endpoint,data,length,toggle)
and
data is a 32 word array of 16 BIT integers
and
the descriptor defines a 64 BYTE endpoint.
Is length 32 or 64? |
32 x 16 bit values == 64 bytes. Where is the confusion? |
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SuperDave
Joined: 22 May 2008
Posts: 63
Location: Madison, TN
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| Posted: Thu Jul 03, 2014 5:14 am |
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Thanks jeremiah.
The function in usb_hw_layer.h is | Code: | | int1 usb_put_packet(unsigned int8 endpoint, unsigned int8 * ptr, unsigned int16 len, USB_DTS_BIT tgl); |
So the data is treated as a byte and the length becomes 64.
I was wondering if a 16 bit processor changed that but it doesn't. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19535
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| Posted: Thu Jul 03, 2014 6:57 am |
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USB, only transfers in bytes. Doesn't make any difference whether the processor is 8, 16, 32 or 64 bits.
The data being transferred is addressed by:
unsigned int8 * ptr
A pointer to a block of bytes. |
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