Currently I am working on Yocto OS for my project. My question regarding debugging. In normal practice, the debug information is sent through the serial port. I aware about ssh debug. I have two questions:
Why does every device normally support debugging over serial port?
Is there any possible way to debug through the USB port (without using serial to USB converter) in Yocto?
Because a serial driver can be simple and implemented without interrupts (it’s how the Linux kernel console actually does). This is a requirement due to emergency cases when crash log should be sent as much as possible and as full as possible.
You have a few options:
a) use a USB-2-Serial and /dev/ttyUSB0, or
b) use a USB-2-Ethernet and setup netconsole, or
c) (only on the newest xHCI hardware with debug capability and with additional code to write) you may enable earlyprintk for USB. Note, it requires special debug cable to be connected (note, the blue colored is not the same, you need the orange one), or
d) USB2 (EHCI), which supports debug capability, requires a special device to be connected in between, which is not needed for USB3 (see option c) above).
Variant c) is partially supported in the v4.13-rc1 Linux kernel, there is HOWTO file (in the kernel source tree Documentation/driver-api/usb/usb3-debug-port.rst).
Related
I would like to use a windows machine as a USB488/USBTMC device. USB488/USBTMC is a reimplementation of the good old GPIB/IEEE-488 on USB rails. But most articles on the topic refer to a Windows machine as a host/controller. The Windows USB stack is not well suited for USB device/USB OTG modes. However, if you look at some of the high-end gear like oscilloscopes and spectrum/network analyzers, it is well known that they are often Windows machines inside with some additional hardware. So, how it is done?
To some background: it is a project to retrofit a very old SEM microscope with new hardware. The current one is a 68k custom system with a CRT that uses a GPIB interface for comm with a PC. Things like sample spectroscopy are done as a BASIC program running on a pc and communicating through that gpib port. The plan is to replace that 68k junk with a modern day windows pc with an FPGA on a PCIe bus. For compatibility reasons, it would be nice to have a usb488 port in the new PC. Though I have no idea of how to do it properly. The only solution I have so far is to have some cheap USB-capable micro hanging on the SPI bus on the FPGA facing side and a USBTDM class on the USB side. But maybe Im missing something and there is a specific thing or chip that exists that can do it that Im not aware of.
I can only speculate how high-end oscilloscopes achieve it. The most likely option is that they use a dedicated chip like a MAX3420E. It is connected via SPI. Part of the USB protocol is implemented by the chip, part of it will be implemented by the oscilloscope software.
Most USB controllers chips found in PCs can operate as the host only. And even if they could do a role swap, Windows (for Desktop) has not supported device/peripheral mode until recently. It now does. See USB Dual Role Driver Stack Architecture. But I don't fully understand it to tell you what hardware you would need to purchase where this feature is enabled.
Role swapping is very common on smartphones. It is also implemented in Linux (search for "Linux USB gadget"). Many Apple Macs can run in Target Disk Mode, which is a USB device/peripheral mode as well.
Working with the STM32L062 Cortex-M0 and CubeMX the generated USB CDC-ACM code works fine in Windows. With loopback code running on the STM32 and TerraTerm running on Windows characters typed in the terminal window correctly echo back. However, when this same system is then plugged into a laptop running Ubuntu, the device fails to enumerate. Even worse, the system doesn't appear to respond to the connection whatsoever- no new messages appear via dmesg that even a failed enumeration is going on. Given that the code used is generated by CubeMX wizards it is difficult to know what to start to troubleshoot. Any suggestions?
As an aside, this isn't the first issue presented by CDC-ACM drivers. Implementing a USB CDC-ACM stack for a PIC32MM processor, data can be sent to the host but not received from the host, however, if the driver is switched to plain vanilla CDC then data can be sent both ways no problem. So it seems maybe Ubuntu has some issues with the default USB drivers, but either way, it's very odd that the ST driver gets zero response at all from the system.
How is it possible to determine the commands to operate a usb device, if that device comes from another operating system and traffic monitoring software cannot be installed on that OS. The only method i can think of is sending random commands to the device, until the device responds, but this seems implausible for more complex commands, and potentially dangerous. For example, consider the DualShock 4 controller. Sony has not made an official driver for this device, so what method can i use to create a linux driver for it?
Get a hardware protocol analyzer. Then you won't need to install any software on the host or device under test. Here is one that I have used:
http://www.totalphase.com/products/beagle-usb12/
I need to communicate with some custom hardware that will use either a FTDI or Silicon Labs usb to serial driver.
I found a couple examples but they are older and was hoping for a more up to date example. Plus, I have been confused by the new AppleUSBFTDI kernel driver in how that works with the IOKit and other chips like the Silicon Labs part. It would be nice to have one program that doesn’t care which driver is used.
I have already looked at this example:
FTDI Communication with USB device - Objective C
The nature of these drivers and devices is that they are supposed to function as a standard serial port virtually over USB. So in terms of access it should be no different than accessing a standard RS232 COM port.
I would suggest reading the Serial Programming Guide for POSIX Operating Systems. I'm not sure what older examples you're seeing but serial access itself is many years old, but the idea behind communicating to the serial device is the same in the case of these USB to serial bridge devices.
For information on some Objective-C frameworks, take a look at this Stack Overflow post.
Finally, here is an article directly from the Apple documentation, Working With a Serial Device, and you'll see it also references the POSIX style API.
You should simply need to install the driver associated with your device and plug it in for this to work. In terms of the Silicon Labs CP210x device just download and install the OSX driver. Then plug in your device. This is where the one difference may show up, the name of the tty device on the system (it will show up in the /dev directory). In the case of the CP210x it will show up and be accessible as tty.SLAB_USBtoUART or cu.SLAB_USBtoUART. This will be the name of the device you should open, then use and API from above to start your communication.
I've got a Windows 8 Professional device which has got a Mobile Broadband adapter embedded and I need to be able to send AT commands to the modem, usually I'd connect to the COM port and send the commands. However the device doesn't appear to have any COM ports, instead it presents its self as a network adapter.
I'm wanting to send AT commands to change the APN of the modem and to reset the device, I've looked into the 'netsh mbn add profile' but this command always returns an error advising that the XML profile is incorrect.
Also from looking at the functions of the netsh mbn it doesn't seem to provide as much control as sending AT commands.
The modem that I'm trying to interface to is the Ericsson C5621 GW on a Lenovo ThinkPad Tablet 2.
Is there another way to send AT commands?
Thanks
I do not know this product in particular, but since I worked in Ericsson, later in ST-Ericsson with mobile phone development for over a decade it is doomed to have some of my code in it so I'll answer on a general basis.
Short version is, no unless the device exposes a serial interface over one of the external interfaces (possible interface types are RS-232, IrDA, Bluetooth, USB or CAIF), there is no way of sending AT commands to it1.
Being an embedded device in a laptop and
your since you say it seems to be without serial interfaces I assume it uses CAIF (commonly used in embedded settings. It could also have be using USB with the serial interfaces disabled, but since this press release mentions that it will be available in a version with PCI interface, that is very unlikely). And thus unless the device is set up with any active VEI channels, there is no ways in for AT commands.
There might be other ways of changing the APN though.
1 We had a debug mechanism to inject AT commands onto arbitrary serial interfaces, but this itself was running on a serial interface, started by an AT command. And besides it will not be present in released products.