I'm trying to interface the Mindwave (http://store.neurosky.com/products/mindwave-1) with my Altys board, through the USB UART port. The dongle I'm trying to connect is basically a wireless reciever that outputs serial data stream on the USB connection. I'm trying to read in this serial stream on the FPGA.
The problem I'm seeing is that when I try to Chipscope the UartRx pin (A16), I see no activity on it even though the dongle is supposed to send 0xAA in standby mode.
Since the FPGA does not power the dongle, I have it connected to an external power USB hub and then connect the hub to the FPGA. However I don't see any activity.
Do I need to convert the signals to another level, or invert them? I thought the EXAR chip takes care of it.
Did you try swapping RX and TX?
Did you have acces to a scope? To check you can repeatly send 'U's (0x55) and look with a scope to see which line is RX and which is TX. You can also check the speed of the interface with this method.
Related
I get lost trying to figure out how to parse control data in CDC_Control_FS() function. Can you point me any documentation about that?
Background:
I am using stm32f103, trying to implement USB CDC communication with HAL libraries. I need to detect if usb port is opened by PC, it should handle power on scenario as well as cable reconnetion during runtime. After some research I think that checking DTR signal may be the (most elegant) solution. I know there is CDC_Control_FS() function that delivers all line configuration to stm32f103 from PC driver, but unfortunately I don't know data format / how to extract DTR signal, to be able to set some flag for indicating that usb port is currently open or closed.
I have a third party device that is UART programmable.
I need to create a USB - UART bridge with a functional password (programming only after entering the correct password)
generated the code using the latest version of STM32CubeMX for Atollic TrueSTUDIO for STM32 9.3.0 ...
I transfer data between USB and UART through a buffer (one for usb-uart, and another one for uart-usb)
when I try to transfer several characters everything is OK, but when I try to transfer a large data packet, problems start due to the fact that the USB speed is much higher than the UART ...
there are two questions:
1.How do I tell USB that I need to stop transferring data and wait until the UART (buffer) is busy
2.How on the side of the microcontroller to get the baud rate set on the PC (set when the terminal is connected to the virtual COM port)
USB provides flow control. That's what you need to implement. A general introduction can be found here:
https://medium.com/#manuel.bl/usb-for-microcontrollers-part-4-handling-large-amounts-of-data-f577565c4c7d
Basically, the setup for the USB-to-UART direction should be:
Indicate that the code is ready to receive a USB packet
Receive a USB packet
Indicate that you are no longer ready to receive a USB packet
Transmit the data via UART
Start over
Step 0: Initial setup
Call USBD_CDC_SetRxBuffer to set the buffer for receiving the USB data. Unless you use several buffers to achieve higher throughput, a single call at the start of the program is sufficient.
Step 1: Ready to receive data
Call USBD_CDC_ReceivePacket. Other than what the name implies, this function indicates that the app is ready to receive data. It immediately returns before the data has actually been received.
Step 2: Receive a USB packet
You don't need to do anything here. It will happen automatically. Once it's complete, CDC_Itf_Receive will be called.
Step 3: Indicate that you are no longer ready to receive a USB packet
Nothing to do here. This happens automatically whenever a packet has been received (and double buffering is not enabled).
Step 4: Transmit the data via UART
I guess you know how to do this. It's up to you whether you want to do it in a blocking fashion or using DMA.
Since a callback is involved, you cannot put this code into the main loop. It might be possible to put all code into CDC_Itf_Receive if blocking UART is used. It would appear in the order 2, 3, 4, 1. Additionally, initialization is needed (0 and 1).
In the UART-to-USB direction, you would need to implement flow control on the UART. The USB flow control is managed by the host. Even though USB is much faster than UART, flow control is relevant as the application on the host can process data as slow as it likes to.
Regarding question 2: I'm not sure I understand it... The microcontroller cannot set the baud rate on the host. Either the host can specify a baud rate (transmitted over USB and applied to UART), or if the UART has a fixed baud rate, you can ignore baud rate (any baud rate set on the host side will work as it does not apply to USB).
I am trying to use the Thrustmaster T-Flight Hotas X joystick with my STM32 f407 Discovery board. As you know, the joystick has a USB connection, but actually I do not know how it transmits data and I do not know what kind of protocol it uses...do you have any advice?
Is there a way to connect the joystick to the board?
Yes, you can use the USB OTG port in host mode to connect your joystick.
The joystick will use USB HID protocol - this is documented in detail at usb.org. Short version: The device tells you in its "report descriptor" how the data is formatted. The data itself is transmitted via interrupt endpoint.
Unfortunately, the software side is non-trivial, as you need host mode on the MCU. Parsing the report descriptor is not required if you only ever use the same joystick model - which can be identified using the VID:PID in the device descriptor.
There should be an appnote with some example code for USB host mode on the STM website, but in order to support your joystick you probably have to make some modifications - which are rather difficult for beginners.
I'm looking to create a device that acts as a host to a USB peripheral, format the data, then send it out to another host (the PC). Are on-the-go chips capable of accomplishing this or would you need to implement both a host USB microcontroller and a peripheral USB controller? I don't see much information out there for creating a middleman that performs data molding for USB prior to reaching a host. Any information would be appreciated, hopefully I didn't butcher this concept.
you should use a microcontroller with 2 USB busses.
One should act as a host, and the other as a slave.
You will need to implement them both.
USB OTG is used to create a host and a slave in 1 device with 1 connector,
so it's impossible to use them together at the same time.
I need to make a program that would play a sound as I press a push button switch. My idea is to use the USB port, and that if I short 2 wires from it (like for example the data+ and data-), the program would play a sound repeatedly while the 2 wires are shorted. Is my idea possible and simple to do? Can you please help me do it using VB? Thanks a lot for any help.
No, that is not practical. USB ports do not have that feature is far as I know. There are plenty of small, cheap USB microcontroller boards that are up to the task though.
For example, you could get an A-Star 32U4 Micro, program it using the Arduino IDE, and make it send a certain message on the its virtual COM port (which is accessed from the Serial object) when a button is pressed and another message when it is released. Then in Visual Basc, you would use the SerialPort class to connect to the A-Star's COM port and listen for that message.
USB ports are mainly used for transmitter and receiver communications for data transfers. They are not used for open or closed switch detection. In order to use a USB port for switch detection, you can used a serial to USB conversion breakout board with a specialized IC chip designed to detect an open or closed switch and communicate this via the USB protocols to send out a communications data transmission that a switch has just been open or closed. Then you would program an application in any language to listen on that USB port for this specific data transmission for a closed or open thrown switch. You can potentially detect about 4 switches opened or closed simultaneously if you want. And this serial to USB breakout board can easily be purchased online at:
https://www.sparkfun.com/products/199