I'm going through the process of coding up an xHC interface following the Intel xHCI guide. I'm at the point where I need to give the controller the memory buffer address for the command ring (using the CRCR_LO and CRCR_HI registers).
However, after I write these values, I am not able to read it back to verify. The documentation indicates that the value will be updated after the next doorbell, but that doesn't seem to happen either.
I do see the CRR bit go high (command ring running), so it's at least doing something. But I am also not getting command responses in my event ring (though I am getting port status change messages in the event ring).
Can someone clarify how this register works? Is there a way to verify that command ring buffer address?
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I am writing a driver for the xHCI and I have been having a problem with the address assignment.
Here's what I am doing:
Reset the controller by writing 1 to the USBCMD.HCRST and wait for USBSTATUS.CONTROLLER_NOT_READY flag to clear.
Set the maximum slots enabled in the config register to 16 (which is the max supported by my xHC).
Allocate the device context base address register on a 64 byte aligned memory location and write that address to the dcbaap register.
allocate scratchpad buffers, write their addresses in an array, then write the address of that array in the 0th entry of the dcbaap.
Allocate a command ring and write its address in CRCR.
Set the R/S bit and wait for the controller not ready flag CNR to clear.
Allocate event ring, and event ring segment table with one entry, and write the address of table in ERSTBA
Then the software waits until a device is connected on port 12, I connect the device to port 12 and I can see the port goes to the enabled state as indicated by PP, CCS, PED being 1, and PR and PLS being 0.
Submit an enable slot command and I get an event on the event ring with a success completion code and a slot ID.
allocate output and input device contexts data structures and initialize them to valid values.
allocate transfer ring and write its address to the input context.
Submit the first address device command with BSR = 1 and I get an event on the event ring with success completion code.
Here is where things go wrong: submit the second address device command with BSR = 0, and I get USB transaction error for the completion code.
In the xhci spec rev 1.2, it says the USB transaction error is the result of a USB3 DPP(Data Packet Payload) Error. I looked in the USB3.2 rev 1 and it said DPP error could happen due to any of the following:
1.CRC incorrect
2.DPP aborted
3.DPP missing
4.Data Length in the Setup DPH does not match the actual data payload length.
I've been trying on this for about 2-3 weeks now and getting nowhere. I did see a post here where someone had this issue with the EHCI and they fixed it by reducing their delays. I tried to do a similar thing but still didn't fix it.
Does anyone have an idea why am I getting this error or how do I go about fixing it?
Something I want to note is that if skip step 8, an continue to enable slot command, I still get the same results. So I still get a device slot and I still get a successful first Address Device command even though there is no device connected. Which makes me think that the usb device isn't even talking? I'm using a thumb drive, I tried different thumb drives and different ports and still the same issue. I'm using a USB 3.0 thumb drive on a SS port.
I was able to make a working HID USB stack on my "StartUSB for PIC" board for the 18F2550 microcontroller. I based it on one of the MLA libraries, which was made for the 18F45K50 (MLA 2018_11_26, hid_custom, picdem_fs_usb_k50.x), but I converted it to work with the 18F2550 (there might have been easier ways, but only learned to work with PIC about 1 month ago). On the host side, I'm using LibUsbDotNet (also here, there might be easier ways - the documentation on this library really sucks) on a Windows 10 machine.
I'm using the HID class, full speed, and all seems to work. Although, I get some random errors on the host PC (see below), but doing one close/re-open cycle on the host side when getting the error is kind of solving it. Dirty, but it works. So I kind of ignore this now.
Win32Error:Win32Error:GetOverlappedResult Ep 0x01
995:The I/O operation has been aborted because of either a thread exit or an application request.
I'm not an expert on USB (yet). But all examples I'm seeing are based on 1) you send first a command to the device and 2) then you retrieve the answer from the device. I did some performance tests, and see that this indeed shows that I can do about 500 cycles/second. I think that is correct, because each cycle, sending command and retrieving answer, each takes 1 msec.
But do I really need to send a command? Can't I just keep reading endlessly, and when the device has somthing to say, it does send the data in an IN transaction, and when not it ignores which creates a timeout on the host side. That would mean that I can poll at 1000 cycles/second? Unfortunately, I have tried it by changing my implementation on the PIC, but I get very weird results. I think I have issues with suspend mode. That brings me to another question - how can I make the device get out of suspend mode (means that not the host, but the device should be triggering this event). I have searched the MLA library for command such as "wakeup", "resume", ... but couldn't find anything.
So, to summarize, 2 questions:
Conceptual: Can I send data from device to host without being requested for it by a command from the host?
For PIC experts: How can I have a device trigger for a wakeup from suspend mode?
And indeed, the answer is Yes on the first question.
In the meantime, I found another link on the web that contains a Visual Studio C# implementation of a USB library including all the source files.
If you're interested, this is the link
This C# host implementation works as a charm. Without sending a command to the device, I get notified immediately if a button is pressed. Great!
It also proofs that my earlier device implementation based on the original MicroChip MLA, is 100% correct. I stress tested the implementation by sending a "toggle LED command" as fast as I could, and I reach 1000 commands/second. Again great!
I think that LibUsbDotNet isn't that perfect after all. As I wrote above, I get rather unstable communication (Win32Error). But with this implementation, I don't get a single error, even after running for half an hour # 1000 commands/second.
So for me, case closed.
I'm trying to start a DMA transfer on my stm32f412, and I've got everything set up to the point where I'm setting the control registers on the DMA channels/streams for TX and RX. I am able to set the enable (Bit 0) on the TX, but not the RX.
The datasheet has 3 options for the bit being cleared by hardware: 1.) On a DMA end of transfer (stream ready to be configured) 2.) If a transfer error occurs on the AHB master buses 3.) When the FIFO threshold on memory AHB port is not compatible with the size of the burst.
I don't think it could be the first or the third, because the DMA transfer hasn't even started yet, and there isn't a burst configured, it's just a single transfer. I'm not quite certain what the second means, but there aren't transfer errors marked in the error registers.
Any avenues to look into would be appreciated
Edit: Ugh, I was looking at the wrong registers for to find the DMA_LISR and _HISR. There was a transfer error on my RX channel.
From the description of DMA_SxCR_EN bit in the reference manual:
Note: Before setting EN bit to '1' to start a new transfer, the event flags corresponding to the
stream in DMA_LISR or DMA_HISR register must be cleared.
In my experience, these event flags include not only the error flags, but also the regular event flags like Transfer Complete or Half Transfer. In some cases, I also ended up clearing FIFO error flag, although I can't remember the reason behind it.
This problem manifests itself as "DMA works only once". In your case, it doesn't work even once, so there can be other problems. Still, I think it's worth trying to clear all the status flags before enabling the stream.
I have a SPI for MSP430 written. If I send WRSR(01h) or RDSR(05h) to M25P64 flash.
The response I get from the Flash SPI_MISO is FFh.
So my question is "Is the response I have obtained is it right?"
How do I come to an understanding that handshaking between my SPI and Flash is correct?
Thanks
AK
Is the response I have obtained is it right?
The response is wrong. 30 seconds on Google and in the datasheet will tell you that. Things to check (since you have not provided any information):
How do I come to an understanding that handshaking between my SPI and Flash is correct?
Is this a new piece of SPI code? If so have you checked with an oscilloscope to see what you send out (clock and MOSI) is what you expect and matches what the datasheet says the device expects? It's the definitive way to be sure.
Does your SPI code work with any other devices?
Are your IO pins configured correctly on the MSP430?
Have you got the SPI module configured correctly for phase and polarity?
Did you forget to assert the chip select line?
What about HOLD?
Did you remember to send a dummy byte after the RDSR command so that the device would send the status register value?
Do you see a response from the device on an oscilloscope? Does the MSP430 read that value or a different one?
You are sometimes better first of all trying to read the device ID rather than the status register for a new piece of code. The reason for that is the device ID will never change, whereas the status register might change (although that depends on the device).
it seems that as soon as data is ready for the host (such as when I use WriteFile to send a command to the HID in which I tell the HID to give back some data such as the port value) and the in packet ready bit is set, the host reads it (as confirmed by another USB interrupt) before ReadFile ever is called. ReadFile is later used to put this data into a buffer on the host. Is this the way it should happen? I would have expected the ReadFile call to cause the in interrupt.
So here is my problem: I have a GUI and HID that work well together. The HID can do I2C to another IC, and the GUI can tell the HID to do I2C just fine. Upon startup, the GUI reads data from the HID and gets a correct value (say, 0x49). Opening a second GUI to the same HID does the same initial data read from the HID and gets the correct value (say, 0x49; it should be the same as the first GUI's read). Now, if I go to the first GUI, and do an I2C read, the readback value is 0x49, which was the value that the 2nd GUI had requested from the HID. It seems that the HID puts this value on the in endpoint for all devices attached to it. Thus the 1st GUI incorrectly thinks that this is the correct value.
Per Jan Axelson's HID FAQ, "every open handle to the HID has its own report queue. Every report a device sends goes into all of the queues so multiple applications can read the same report." I believe this is my problem. How do I purge this and clear the endpoint before the 1st GUI does its request so that the correct value (which the HID does send per the debugger) gets through? I tried HidD_FlushQueue, but it keeps returning False (not working; keep getting "handle is invalid" errors, although the handle is valid per WriteFile/ReadFile success with the same handles). Any ideas?
Thanks!
You might not like this suggestion, but one option would be to only allow one GUI at a time to have an open handle. Use your favorite resource allocation lock mechanism and make the GUIs ask for the HID resource before opening the handle and using it.