What are the best tutorials and API's for Linux and C based USB programming? I want to be able to transfer data at max throughput point to point between two PCs, with USB 3.0.
Load the Ethernet over Usb kernel driver (a howto for setting up one machine is here), set up static IPs on both ends, and use rcp.
You can't connect two Hosts directly over USB, one side must have a device controller (such as the NetChip 228x), in which case you can load the g_ether module (enabled with USB_ETH) and do as suggested by gnud
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I'm using a LPC178 development board and I want to read a file present on a Windows PC. My dev board only has a RS2323 interface to communicate with.
How can I go about transferring the file from my PC to my MCU using a RS232 (serial) link? I found a reference which explains how to transfer data between a MCU and PC but it isn't about file transfers.
Afaik there is no easy solution for this like calling something like "copy" or "fopen" over RS232. I would be happy to be proven wrong here.
The fastest solution might be to write a little programm running on your Windows Host, which listens to your RS232 communication and pipes your communication into/out of the file based on your communication protocol. This can be done with standard file operations in the language of your choice, for example C, C++ or Python.
Your problem is one of the oldest in the book. How do you transfer files without fancy operating system abstractions. For RS232 (or any other serial method) there exists many file transfer protocols.
One of them is kermit. This is a protocol from 1981 and can transfer binary and text files. It is able to be embedded in a micrcontroller and there exists programs to transfer/receive using kermit.
alternative old site for reference
In the simplest case you would use a file transfer protocol such as XMODEM, YMODEM, ZMODEM or Kermit - these protocols were designed in the days before networking and the Internet were ubiquitous and deal with simple point-to-point transfers between two computers. They are supported bu most terminal emulator tools such as TeraTerm Pro or PuTTY so no specific PC software need be written, just the microcontroller end.
A more complex but flexible solution is to implement a TCP/IP stack and a PPP driver, and an FTP application layer - probabaly only practical if using a third-party TCP/IP stack and application layer. You can then use any FTP client for the PC end, so again no PC software required. While this may be overkill if all you need to do is transfer files, it has the advantage of allowing you to use the the single serial port concurrently for other data streams and application protocols such as Telnet. The disadvantage perhaps is that while Windows does support PPP it is buried within the dial-up networking and to be frank a pain to get working.
Very first step you have to do is ensure serial communication is working fine.
Send a byte continuously from mcu to PC and display it on some io console (for example: HyperTerminal, Dock light )
Receive a byte to mcu from PC and echo it back to PC.
Once you are sure that serial communication is working fine then select some file transfer protocol and implement it.
While you can select any of the available protocols or write your own protocol and implement it.
For purpose of discussion i select Xmodem protocol.
If you consider some other protocol you may stop reading answer here.
XMODEM is a simple file transfer protocol.
Refer http://web.mit.edu/6.115/www/amulet/xmodem.htm for detailed information.
You may implement Xmodem mcu side by reading protocol. Or may consider using open source also ( if available )
PC side i prefer to use HyperTerminal io console as it is compatible with Xmodem.
In HyperTerminal all that i have to do is configure settings and select file for transfer to mcu.
Now transfer any file to mcu using Xmodem protocol from PC.
What you do with received file in mcu is up to you : )
I wish to write a Linux device driver which spawns a thread which listens to the comport on /dev/ttyAMA0.
On the comport is an rf device which connects to a host of other devices. I wish I add each rf device as I discover them as if they were physical devices to Linux and upon probing the parameters of each device add files for controlling the device parameters.
I have done quite a bit of searching around this and have already done many of the simple hello world driver tutorials and found how to spawn threads from within a driver.
I already know how to read/write to the comport from user-land c.
My question is; is this approach OK? i.e. a driver which can spawn multiple devices. Should this instead be a service? How about reading/writing to the comport from another device is this ok? What are the best practices? Examples?
N.B. I realise I will have to control access to the comport. I am choosing to ignore that complexity for the moment, but I will achieve this via some sort of semaphore.
This is for a personal project by day I'm mainly a c# developer.
EDIT
I have found this related question, I don't however believe it to be a duplicate. I think recommends not to write drivers over drivers. But I wish to add these external devices as if they were physical devices.
Non-programmable Xbee modules should be configured through a PC (with XCTU) or other devices like Arduino... but can the programmable xbee modules (like xbee-pro zb s2b) autoconfigure themselves, without being connected to another device like a PC or Arduino, by running code stored in their memory?
I mean, can they run orders like the ones you run through XCTU but programming them in the internal memory code? Like scan energy of every channel, select a channel, set a PAN ID, configure the different parameters of the device...
Thank you
Yes, the development kit includes an API for sending AT commands from the co-processor to the radio on those boards.
There's also a passthrough mode that relays the host computer serial port through to the radio processor, which can help with initial setup/configuration of the modules like you might do during manufacturing.
To answer your question:
I mean, can they run orders like the ones you run through XCTU but programming them in the internal memory code?
No. You can not program a sequence of orders/commands into the internal memory of the device. To do anything meaningful the device needs to be "driven" from a host PC or MCU that can send the AT Commands.
If you want 1 device solution that does not require a Host MCU then you will need to use a ZigBee SoC (System on Chip), such as the CC2538 - http://www.ti.com/product/cc2538 running a ZgBee SDK (Software Development Kit) - http://www.ti.com/tool/z-stack (ZStack-Home). However this will require you to develop the ZigBee application SW.
Regards,
TC.
My question is going to be rather vague but I will try to explain as detailed as I can what I am trying to resolve.
Trying to learn Linux kernel USB stack I have started to think of making a simple USB driver for my Atmel evaluation board based on ARM M0+ MCU to run away from Windows tools (Visual Studio plugin).
I have spent few days learning kernel's USB API and come to conclusion of how to make this. My driver aims to make my board connected to PC through USB cable act like a simple USB flash drive. Making that I then can easily program it with a new version of firmware written by me.
I have found that I need to find out specific interface (I am talking about interface in terms of USB specification, not interface we used to use as a code abstraction) that holds an endpoint (pipe) responsible for interaction with flash memory. And then I can map it to character device and interact with it using standard I/O operations that are described in struct file_operations structure.
Simply using cat on /proc/* file descriptor that was created by USB Core subsystem I have investigated that interface responsible for interaction with flash memory holds bulk endpoint (likewise, this terms come from USB specification, CMIIAW) that act as a "descriptor". Linux kernel USB Core subsystem gives neat interfaces to talk to different kind of endpoints whether it control, interrupt, bulk or asynchronous endpoint.
Now I have come closer to my very question.
Also the main transfer unit in communication between two USB devices is abstraction called urb - you allocate it, you fill it, you send it to USB Core subsystem, you read it if it was IN type of urb and, finally, you free it. What is confusing for me and tightly related to my question is the next API include/linux/usb.h:
static inline void usb_fill_bulk_urb(struct urb *urb,
struct usb_device *dev,
unsigned int pipe,
void *transfer_buffer,
int buffer_length,
usb_complete_t complete_fn,
void *context)
Assume I have obtained an information from board's datasheet about where to write a program code. Let's say, we have 0x00100 - 0x10000 memory region. I will compile my code, obtain a binary and then using standard Linux tools or writing a simple user-space wrapper application I will use lseek to set file's offset to 0x00100 and write system call provided with a buffer (binary compiled previously) and it's length.
In kernel space, I will have to allocate urb in write system call handler, fill it with a buffer sent from user space and submit this urb to USB Core.
BUT I can not find a way how to specify an OFFSET set earlier by lseek. Do I miss something? Maybe I missed some concepts or, perhaps, I am watching in a wrong way?
When your embedded Linux device acts as a USB mass storage device, the flash as a peripheral on Linux device is unmounted, and the gadget driver is loaded. Linux then loses control to the flash, and now the PC connected to your Linux device fully controls the flash. This is because a flash as a USB device can only has one USb host.
The gadget driver works purely in kernel space. It does not receive or transmit data from/to user space. It calls vfs_read() and vfs_write() to access the files on the flash, with an field offset. The offset is got from the USB commands sent from your host - Windows PC.
There is no way to specify offset using USB subsystem's API. I misunderstood whole conception of USB as communication protocol, unwise me. You must first learn underlying protocol your device uses to communicate with others.
If your device acts as a USB HID device then learning specification of how to exchange data with USB HID device is the way to go. If there is something proprietary then you can do nothing but reverse engineer it (listening USB packets with a sniffer on system where a driver for your device exists).
As for my board it has embedded debugger that serves as a communication module besides being debugger itself. Specifically, my device is equipped with EDBG and here is a link on description of protocol it uses for communication.
I am doing IO programming in C in Ubuntu. And I need the base address of the port to write data.
My laptop dont have a parallel port. So I bought a USB to Parallel port connector. I plugged in the device and its getting detected in /dev/usb/lp0
I ran "lsusb" to see the list of devices and I can see the ID also. But how can I get the base address ? For the usual hardware parallel devices, the base address is 0x0378. this address is not getting detected while using USB to Parallel device.
Please help.
A USB parallel port doesn't have a base address - it's not a meaningful concept for USB. I'm afraid the days of doing I/O on PC hardware via in and out instructions ended a few years ago, though lots of old tutorials still survive on the web.
You can write bytes to the parallel port as a character device, and these will appear on the printer port pins. The USB adapter will expect the other end to handshake data exactly like a printer. If you want to do general I/O prototyping, you're probably better off with a simple USB microcontroller like an Arduino.
Further discussion here.
If you are still interested to use this USB-to-parallel-printer device for your own bit-banging, it's important to know that their built-in firmware always allows controlling of D0..D7, INIT (as outputs), /ERR, ONL, PE (as inputs), but never for /ACK, BUSY (inputs), /STB, /AF, /SEL (outputs) pins.
And you need an 8-bit latch (e.g. 74HCT574) for catching data while strobing.
See here (https://www-user.tu-chemnitz.de/~ygu/bastelecke/PC/USB2LPT/faq#DIY)
especially for possible data rates.
Accessing from software side is a bit complicated but possible, and you may have to re-structure your software and hardware for making such adapters useable. I don't know for Linux case how to access, but IMHO you don't need to write a kernel-mode driver.