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Discussion Groups | LPC2000 | Setting up DMA transfer using LPC2148
Discussion group dedicated to the Philips LPC2000 family of ARM MCUs
Setting up DMA transfer using LPC2148 - Charly - Oct 27 0:33:50 2007
Hi all,
I need to transfer large amount of data via Bulk Endpoint with DMA to a
USB Host.
1. How exactly is the communication between USB Host and Device (LPC)
to the DMA-enabled endpoint?
For example,
A. Host is already requesting for data and therefore IN token is sent
to device but device does not have data yet to transfer. What interrupt
takes place? isit NewDD interrupt? INAK-BI? how is the mechanism of new
DD interrupt? if slavemode is disabled, how can we receive Interrupt to
indicate host request?
B. Device has data to send to host, but host has not requested. Should
the DMA be enabled at this point? or device need to wait for host to
request then enable the DMA?
Basically Im stil not clear in terms of the set of messages/interrupt
that should happen during the process (from Host or Device) and how
should they be handled
2. In the DMA Descriptor, what is the content of Word 2? address of the
databuffer? can the databuffer located outside of the USB_RAM? or
databuffer needs to be copied first into USB_RAM before enabling DMA?
3. if data tobe transffered is greater than 64 bytes, does it mean it
requires more than one DD to transmit? do we have to prepare all DDs
(for example 4 DDs to transfer 64*4 bytes) before we actually send (or
enable the DMA)?
Regards
Charly
(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )
I need to transfer large amount of data via Bulk Endpoint with DMA to a
USB Host.
1. How exactly is the communication between USB Host and Device (LPC)
to the DMA-enabled endpoint?
For example,
A. Host is already requesting for data and therefore IN token is sent
to device but device does not have data yet to transfer. What interrupt
takes place? isit NewDD interrupt? INAK-BI? how is the mechanism of new
DD interrupt? if slavemode is disabled, how can we receive Interrupt to
indicate host request?
B. Device has data to send to host, but host has not requested. Should
the DMA be enabled at this point? or device need to wait for host to
request then enable the DMA?
Basically Im stil not clear in terms of the set of messages/interrupt
that should happen during the process (from Host or Device) and how
should they be handled
2. In the DMA Descriptor, what is the content of Word 2? address of the
databuffer? can the databuffer located outside of the USB_RAM? or
databuffer needs to be copied first into USB_RAM before enabling DMA?
3. if data tobe transffered is greater than 64 bytes, does it mean it
requires more than one DD to transmit? do we have to prepare all DDs
(for example 4 DDs to transfer 64*4 bytes) before we actually send (or
enable the DMA)?
Regards
Charly
(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )