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Hi,
I'm using uVision 4 with the MCB2300 development board. I'm developing a software that periodically transmits data (status information) from the device to the host (as first step, the data are sent without being explicitly requested by the host as soon as a connection has been established). Thereto I've modified the USBCDC example included with uVision. The software transmits 20 bytes periodically, using USB_WriteEP (in usbhw.c, which uses the register interface). This works fine so far. Now I would like to use the DMA engine to avoid copying the bytes word by word into the register. I've enabled DMA in the USB configuration for logical IN endpoint 2 (physical endpoint 5 which is called CDC_DEP_IN in the example), and I have managed to set up DMA descriptors. But how do I trigger a DMA transfer? I've tried several combinations of USB_DMA_Setup and USB_DMA_Enable. Manually setting the appropriate bit in DMA_REQ_SET to trigger the interrupt results in an error state. What am I doing wrong? Could anyone please give me some hints concerning USB DMA? Thanks a lot. I'll be back in January, after my Christmas vacation. I wish everybody a merry Christmas and a happy new year!
CC
unfortunately it seems to be very complicated to use ZLPs....
void SendDataToHost() { USB_DMA_DESCRIPTOR DD; DD.BufAdr = (unsigned int)pStartBufAddr; /* DMA Buffer Address */ DD.BufLen = 256; /* DMA Packet-size */ DD.MaxSize = 64; /* 64Byte for bulk-transfer */ //DD.Cfg.Type.IsoEP = 0; //DD.Cfg.Type.ATLE = 0; DD.Cfg.Val = 0; /* Initial DMA Configuration */ USB_DMA_Setup (CDC_DEP_IN, &DD); /* Setup DMA */ /* ************* ZLP **********/ DD.BufLen = 0; DD.MaxSize = 64; DD.Cfg.Val = 0; USB_DMA_Setup (CDC_DEP_IN, &DD); USB_DMA_Enable(CDC_DEP_IN); /* Enable DMA */ LPC_USB->USBDMARSet = 1 << EPAdr(CDC_DEP_IN); }
With this code my usb device will send only 0-byte packets to the host; even if the host didn't open the serial port....
"DD.Cfg.Type.Link = 1" must be, for chained DD.
If I will call the SendDataToHost() method immediately after the last one, then I have to use Link = 1? How can I determine if the dma is still in progress with the last descriptor?
void test() { SendDataToHost(); //tx 400bytes SendDataToHost(); //tx 400bytes SendDataToHost(); //tx 400bytes } /* timer isr will be called every 20ms */ void Timer0_ISR() { test(); }
If I will do this, only 384-bytes will be transmitted instead of 400bytes. If set the "DD.Cfg.Type.Link = 0".
DMA Descriptors are managed in a linked list, for each endpoint. When USB_DMA_Setup() is called with "DD.Cfg.Type.Link = 1", on the same EP, new DD is chained after the last one.
void SendDataToHost() { USB_DMA_DESCRIPTOR DD; DD.BufAdr = (unsigned int)pStartBufAddr; /* DMA Buffer Address */ DD.BufLen = 256; /* DMA Packet-size */ DD.MaxSize = 64; /* 64Byte for bulk-transfer */ //DD.Cfg.Type.IsoEP = 0; //DD.Cfg.Type.ATLE = 0; DD.Cfg.Val = 0; /* Initial DMA Desc Configuration */ USB_DMA_Setup (CDC_DEP_IN, &DD); /* Register DD */ /* ************* ZLP **********/ DD.BufLen = 0; // Zero-Length DD.MaxSize = 64; DD.Cfg.Val = 0; // Clear config parameters DD.Cfg.Type.Link = 1; // link this DD after above first DD <-------- Add this line USB_DMA_Setup (CDC_DEP_IN, &DD); /* Register DD */ USB_DMA_Enable(CDC_DEP_IN); /* Enable DMA */ LPC_USB->USBDMARSet = 1 << EPAdr(CDC_DEP_IN); }
> How can I determine if the dma is still in progress with the last descriptor?
Raise a flag in SendDataToHost(). In USB_EndPoint2() callback, catch (event == USB_EVT_IN_DMA_NDR) and drop the flag
Tsuneo
Hi Tsuneo,
do you know a suitable solution to determine the time when the host is ready to receive the first byte of data?
As well as, I'm searching for a good solution to switch between receive / and transmit data. The LPC processor is able to receive or to transmit data but both directions are not possilbe at the same time. Is it a good point to add a additional HID interface with one endpoint(in) so that I can change the direction?
> do you know a suitable solution to determine the time when the host is ready to receive the first byte of data?
PC application should actively notify the timing to the device. As you are working on CDC,
a) PC application sends a command (start / stop data streaming) over serial TX The device receives this command over the bulk OUT EP.
b) PC application enables / disables DTR The device receives Set_Control_Line_State request
Just after enumeration, usbser.sys (Windows CDC driver) drops DTR by Set_Control_Line_State CloseHandle() of the device handle also drops DTR by Set_Control_Line_State CreateFile() does nothing for DTR > The LPC processor is able to receive or to transmit data but both directions are not possilbe at the same time.
Endpoints run concurrently, time-shared in the split unit of transaction. Then, even whille your device sends long long data over the bulk IN EP, the bulk OUT EP can receive commands from PC application. LPC hardware also runs in this way, including DMA.
That means you will have to disable the usb interrupt, setting up the flag together with the usb dma descriptor in the SendDataToHost method. And easily drop the flag in the endpoint USB ISR. IS it not possible to miss an important usb interrupt during the settin up a new dma descriptor?
void SendDataToHost() { //set up dma descriptor //disable usb interrupts //if flag is set -> add Link = 1 USB_DMA_Setup (CDC_DEP_IN, &DD); //enable usb interrupts again /* and these two lines must only be called if the flag was not set... right? */ USB_DMA_Enable(CDC_DEP_IN); /* Enable DMA */ LPC_USB->USBDMARSet = 1 << EPAdr(CDC_DEP_IN); }
a) PC application sends a command (start / stop data streaming) over serial TX The device receives this command over the bulk OUT EP. Which command would that be - start transmitting/receiving?
::CreateFile() SetCommState (); Readfile() or Writefile() - is there a call to the usb device?
is it possible to get the number of bytes which were received by the last packet to determine if the packet was a normal data packet or a command packet? Is it also possible to use USB_ReadEP() because I will also use DMA for the BULK out endpoints?
void EndpointISR() { /* use of dma */ if(event & USB_EVT_OUT_DMA_EOT) { /* End of Transfer */ if (USB_DMA_BufAdr(CDC_DEP_OUT) != ((unsigned int)DataBuf0 + DataIn0)) { /* Data Available */ /* determine if the rxd data is a cmd or a dmx data pkt */ /* is it possible to get the size of the rxd packet to determine if the packet is a data packet or a command packet? */ if(command_pkt) { USB_ReadEP(CDC_DEP_OUT, &CommandReq[0]); SetupCommand(&CommandReq[0]); return; } } } if (event & (USB_EVT_OUT_DMA_EOT) | (USB_EVT_OUT_DMA_NDR)) { /* End of Transfer or New Descriptor Request */ DD.BufAdr = (unsigned int)DataBuf0 + DataIn0; DD.BufLen = DATA_TX_PKT_LEN; DD.MaxSize = 64; /* 64Byte for bulk-transfer */ DD.Cfg.Val = 0; /* Initial DMA Configuration */ USB_DMA_Setup (CDC_DEP_OUT, &DD); /* Setup DMA */ USB_DMA_Enable(CDC_DEP_OUT); } /* 2) */ if(event & USB_EVT_IN_DMA_NDR) dmaInProgress &= ~(1 << EPAdr(CDC_DEP_IN)); }
>> Raise a flag in SendDataToHost(). In USB_EndPoint2() callback, catch (event == USB_EVT_IN_DMA_NDR) and drop the flag
> That means you will have to disable the usb interrupt, setting up the flag together with the usb dma descriptor in the SendDataToHost method. And easily drop the flag in the endpoint USB ISR. IS it not possible to miss an important usb interrupt during the settin up a new dma descriptor?
Keil's USB_DMA_Setup() expects that the DD linked list is not touched by the firmware while DMA is going on the target EP. Therefore, while above flag raises, your firmware should not call SendDataToHost() for new transfer.
If you want to run the linked list dynamically, you'll need more elaboration in the USB_DMA_Setup() - Firstly, reserve a new DD on USB_RAM, populate it by the function parameter (Next_DD_valid = false). - If there is no DD on the linked list, assign the new DD as the top of the linked list. - Else, find the tail DD on the linked list of the EP - - Fill Next_DD_pointer on the tail DD with the new DD - - Raise Next_DD_valid on the tail DD - checks EPxx_DMA_ENABLE bit for the target EP, by reading USBEpDMASt register. - If the bit drops, enable it by calling USB_DMA_Enable() routine. For IN EP, start DMA manually, like above post.
> is it possible to get the number of bytes which were received by the last packet to determine if the packet was a normal data packet or a command packet?
The byte size of received transfer is written-back to the DD for OUT EP.
> Is it also possible to use USB_ReadEP() because I will also use DMA for the BULK out endpoints?
No. USB_ReadEP() is not available for the OUT EP, while DMA is enabled on the EP.
I'm back from Christmas vacation and first want to thank you all for your replies. And I have some good news: my example works now. My solution was almost correct, the only problem was that the data buffer the DMA descriptor points to was not located in USB RAM (obviously this is required - thanks for the hint). I've moved it to USB RAM (a higher region starting at 0x7fd01f00), and now my code works as expected. The next thing I'm going to do is to implement DMA for OUT endpoints...