I have a computer that needs to constantly scan online information and then in accordance to what has been found, the micro controller ( assume an ardunio ) will act in a particular way.
However it seems that most micro controllers cannot be dynamically updated via USB cable. Is there a way to constantly give new instructions or commands to a previously uploaded program into the processor to make it do corresponding actions?
Thank you (I'm sorry if this isn't the right forum to post this question, but I couldn't find one for micro controllers :( )
However it seems that most micro controllers cannot be dynamically updated via USB cable
if you mean programming the microcontroller via usb then it is possible but not at all necessary. you could just send predefined instructions via USB (using LUFA for example) or UART (supported on most microcontrollers) or other data transfer protocols in order to change the state of your program on the hardware side.
if you're new to microcontrollers you should read one of many online tutorials on the subject. arduinos are specially designed for beginners and they have their own forums where you could ask questions. if you choose to go with AVR, i would recommend avrfreaks.
Use serial communications. Install a special driver found on mbed, and then also use PySerial to be able to constanly update the mbed (Any other microcontroller would work)
Related
I recently acquired a Microchip EVB USB7252. I can use it as a USB hub. There are some pins on the board, and I have been looking for ways to use these as an interface between my computer and other devices (preferably my LCD screen).
So I got the IDE + compiler that is supposed to work for this product (MPLAB), but I could find no way to choose my model and get the correct target board.
I was hoping anybody (with likely more experience than me) could steer me in the right direction here. My only previous experience with dev boards is Arduino, where boards show up automatically as COM ports in the IDE. My ultimate goal here is to connect my peripherals to USB without using virtual COM-ports.
https://www.microchip.com/en-us/development-tool/EV33X03A
You can Try The IDE call "MPLAB" you said
and i think arduino CANT use "Microchip EVB USB7252"
So Try it And Good luck
It's a long way because USB is not easy protocol. You need to read USB specs first. Take a look at http://www.usb.org. Generally USB communicate between host and devices. There is special protocol used in this communication.
Perhaps the easiest way to do this will be using Linux and libusb or similar library. When you achieve some experience with this protocol you may be trying to write your own USB driver. I could also recommend to analyse some USB stacks like in Linux or in U-Boot one first.
If you have possibility then I'd also try to use some hardware/software USB protocol analyzers for some overview how does the communication look like.
I've been looking for a detailed description for how USB protocol and cabling works for a long time with no luck. I am looking for a detailed yet not overcomplicated explanation of how things work on the software and hardware side of USB. Links and explanations would be appreciated. I've really run out of ideas, so it would be great if you can help me out.
This is what I do know:
USB hardware carries 4 lines- 5V power, ground, and 2 full duplex lines.
When connecting, the device can ask for a specified amount of current.
The transfer speeds for USB are quite fast compared to traditional serial connections.
When connecting, a device will output descriptors to the host describing itself. These descriptors will also be used for data.
What I don't know:
How does a program in C/C++ write directly to a USB port? Does it write to an address in the port?
How do some devices describe themselves as HID?
How do drivers work?
Everything else...
Thank you!
Identification
Every device has a (unique) Vendor and Product ID. These are provided (sold) by usb.org to identify a device. You can use a library like libusbx to enumerate all connected devices and select the one with the Vendor and Product ID you are looking for.
HID Descriptors
The point of HID descriptors is actually to do away with drivers. HID descriptors are a universal way of describing your device so you don't need to waste time on a driver for every system/architecture/etc/. (Same concept as the JVM.)
Reports
You will use either the input, output, or feature reports to read or write to your device. You send a stream to your device on the input or feature report. This is typically 8 bytes I believe. Only one of which is a single character you wish to write. The HID descriptor contains all the information you need to put together a report. Although I'm struggling to find a related link to clarify this.
Potential Libraries
In an effort to be open-minded here are all the libraries I am familiar with and some info about them.
libusb-0.1
First off is libusb-0.1. This used to be the go to and was built in to many Linux kernels and Windows I believe. It is very easy to use and there is a lot of documentation. However, the owner never updated and it wasn't edited for many years. It supports only synchronous transfers. (If an error occurs, the program can wait infinitely while it expects a transfer.)
libusbx
Next is libusbx. This is what most people would suggest today and I agree. It was published by those frustrated by the owner of libusb-0.1. The code is much more lightweight, up-to-date, and importantly does not require root privileges like libusb-0.1 and libusb-1.0 (Discussed in a second). It supports synchronous or asynchronous transfers.
libusb-1.0
Then there is libusb-1.0. This was the first update to libusb-0.1 in some number of years. It is not compatible with libusb-0.1. This was published the same day as libusbx as a retaliation (I assume) and an attempt to rectify the lack of updated content and conserve a user-base. It supports synchronous or asynchronous transfers.
hid.h
Finally, there is the hid library. This was built on top of libusb as another layer of abstraction. But honestly, I think it's just really confusing and it just adds more overhead than necessary.
Some Good Resources
Understanding HID Descriptors
Control Message Transfer Documentation (Very Good Link IMO)
Rolling Your Own HID Descriptor
Good Visual of HID Reports for Transfers
Great List of bmRequestType constants (You will need this or similar)
A simple terminal app for speaking with DigiSpark using libusbx and libusb-0.1
I know this isn't exactly what you are looking for, but maybe it will get you started!
This website has a general overview of how USB devices work:
https://www.beyondlogic.org/usbnutshell/usb1.shtml
Particular sections give answers to things from the list of things you don't know yet about USB.
E.g. to find out how USB devices identify themselves, read about USB descriptors:
https://www.beyondlogic.org/usbnutshell/usb5.shtml#DeviceDescriptors
To learn how a C/C++ program can talk to a USB device, see examples on using the libusb library:
https://github.com/libusb/libusb/tree/master/examples
To learn how USB drivers work, see a tutorial from Bootlin:
https://bootlin.com/blog/usb-slides/
I want to program a microcontroller (AVR) to control some leds through USB. It's just out of interest in how to build and program USB devices.
There are some AVR microcontrollers that support the USB protocol or I could implement the USB protocol in an another microcontroller myself, but I wonder what to use to write your own drivers on the computer.
My level in system programming: total noob (hence the question)
So what is the literature you people would advice to get good knowledge of the USB technology and how to write your own drivers and beyond?
P.S.: I know:
C (probably will need it here)
Java (probably won't need it here)
Python (hope can use it here)
assembler (hopefully won't need it here XD).
...
P.P.S: driver development differs for different OS's. I use Linux and Windows, so any material related to one or both of these systems is welcome.
Well, although you can develop and write your own USB driver, the beauty of USB is that you don't need to write your own driver. the USB Implementers Forum has defined class specifications for all the standard device classes. If you can make your device fit into a standard device class the driver has already been written for you!
If you truly want to become familiar with USB development, you should start by reviewing the USB approved class specification documents.
If you are into framework for AVR microcontrollers with hardware USB then take a look into LUFA, and if you are into AVRs with software USB then look into V-USB. They have both implemented many USB classes so you don't have to do it on your own - just use them.
That sounds like a great project! I'd suggest starting off with something a little simpler since you're - as you say - a "total n00b". I'm not sure what hardware you currently have (or have in mind) but what I would suggest for the total beginner is the STK500. It's a development board that's very well supported in both Linux and Windows and will give you the most flexibility. It comes with LEDs and switches built in for your projects, but you will need to get a microcontroller. And for that I recommend the ATMega32, a great multi-purpose IC that's also well supported and has lots of documentation on the web.
Once you get those I suggest you do your development on Linux using avr-gcc (make sure to also install avr-libc). If you're using Ubuntu it's easy to get all the packages you need:
% sudo apt-get install gcc-avr avr-libc avrdude
Those should get you up and running. I'd suggest Googling around for help writing your first programs but another good resource is the online materials for this class at Cornell.
That's enough to get your feet wet with AVR microcontrollers and the development tools. The sky is the limit at that point but since you said you want to get into USB I'd suggest using the excellent V-USB framework to have your ATMega32 act as a USB device. After that, as they say, the steps to flipping LEDs are a piece of cake :).
I wonder what to use to write your own
drivers on the computer
libusb (here, here and here)
wdk
WinDriver
For libusb variants info read this
You could us libusb. It's powerful and cross-platform.
But what you're trying to do is a rather simple control interface. You can sidestep most of the complexity by using HIDAPI, I think.
http://www.signal11.us/oss/hidapi/
HID devices often use generic drivers that come packaged into the OS. That way you don't actually have to write any drivers ever, you just make your device compliant with the generic driver and tailor the client software to it.
I think this is what's usually done in the hobbyist electronics field, which is what you're interested in here.
HIDAPI is even recommended for simple communications with HID devices in the libusb FAQ since its a bit more complicated to do it across platforms using libusb.
One good way to go is just to develop a HID device, since the driver is built in to most higher level OSes and pretty flexible for simple IO like you are talking about. Another good option is just using a USB RS232 device or software. I use PICs which have a number of nice devices with USB onboard.
I had built my own test bed based on the ARDUINO UNO and i was using the ionlabs programmer of type usbasp and it worked perfectly fine but it did not allow to convert the TTL back to Rs-232 and hence i couldn't use the features such as serial.print() and i had to install the ftdi cable which allowed me to do this.
The drivers were the libusb 1.xx working just fine.
If you want to program the AVR you can use the ARDUINO software bundle or the stino to upload the programs.
You need to know c(only basics).
I created a USB-keyboard adapter last year for my capstone. I did not do the host programming but used existing code that you can find on the web.But I did program the device side and for that I got a lot of help from this website Teensy Look into their "Code Library" which has code for Keyboard, Mouse and others. Also, the USB protocol handbook will always be useful and you should always consult it when you are doing stuff with USB.
I wonder whether your AVB acts as a host or device. I guess your board is a usb device and you need to light the leds on your board. So, it may be a good way to initialize your board as a HID device. To achieve this goal, you need a HID gadget software stack running on your board. References as follows:
gadget framework in uboot
HID specefication usb org
debug tools such as USB Protocol Analyzer
libusb running on Host PC to send packets
The Microsoft documentation area of the WDK (Windows Development Kit) is recently available on MSDN. There is a section on USB, though you would be best to read the earlier sections first, in particular the "Getting Started" areas. They assume you'll be using C as the programming language for driver development.
WDK Site
WDK - USB Section
For Linux, the Linux USB website should be able to point you in the right direction. In particular you'll want the Programming Guide for Linux USB Device Drivers.
I have been tasked to write a device driver for an embedded device which will communicate with the micro controller via the SPI interface. Eventually, the USB interface will be used to download updated code externally and used during the verification phase.
My question is, does anyone know of a good reference design or documentation or online tutorial which covers the implementation/design of the USB protocol stack/device driver within an embedded system? I am just starting out and reading through the 650 page USB v2.0 spec is a little daunting at the moment.
Just as a FYI, the micro controller that I am using is a Freescale 9S12.
Mark
Based upon goldenmean's (-AD) comments I wanted to add the following info:
1) The embedded device uses a custom executive and makes no use of a COTS or RTOS.
2) The device will use interrupts to indicate data is ready to be retrieved from the device.
3) I have read through some of the docs regarding Linux, but since I am not at all familiar with Linux it isn't very helpful at the moment (though I am hoping it will be very quickly).
4) The design approach, for now at least, it to write a device driver for the USB device then a USB protocol layer (I/O) would reside on top of the device driver to interpret the data. I would assume this would be the best approach, though I could be wrong.
Edit - A year later
I just wanted to share a few items before they vanish from my mind in case I never work on a USB device again. I ran into a few obstacles when developing code and getting it up and running for the first.
The first problem I ran into was that when the USB device was connected to the Host (Windows in my case) was the host issues a Reset request. The USB device would reset and clear the interrupt enable flags. I didn't read the literature enough to know this was happening, thus I was never receiving the Set-Up Request Interrupt. It took me quite a while to figure this out.
The second problem I ran into was not handling the Set-Up Request for Set_Configuration properly. I was handling it, but I was not processing the request correctly in that the USB device was not sending an ACK when this Set-Up Request came in. I eventually found this out by using a hardware USB protocol analyzer.
There were other issues that I ran into, but these were the two biggest ones that took me quite a while to figure out. The other issue I had to worry about is big-endian and little-endian, Freescale 9S12 vs USB data format (Intel), respectively.
I ended up building the USB device driver similar to UART device drivers I had done in the past. I have posted the code to this at the following URL.
http://lordhog.wordpress.com/2010/12/13/usb-drive
I tend to use structures a lot, so people may not like them since they are not as portal as using #defines (e.g., MAX3420_SETUP_DATA_AVAIL_INT_REQR 0x20), but I like them since it makes the code more readable for me. If anyone has questions regarding it please feel free to e-mail and I can try to give some insight to it. The book "USB Complete: The Developer's Guide" was helpful, so long as you knew what areas to concentrate on. This was a simple application and only used low-speed USB.
While writing a device driver for any interface (USB, Parallel port, etc...) the code needed to be developed would depend upon whether there is any Operating System(OS), RTOS running on that Processor/Micro controller.
e.g. if thats going to run say WinCE - It will have its own Driver development Kit , and steps to be followed in the device driver development. Same for any other OS like Linux, symbian.
If its going to be a plain firmware code(No OS) which is going to control the processor/microcontroller, then it's a different situation altogether.
So based on either of the above situation u are in, one needs to read & understand:-
1.) The Hardware Specification of the processor/micro controller development board - Register files, ports, memory layout, etc.
2.) USB spec
3.) Couple of pointers i found quickly. Google shud be ur friend!
http://www.lrr.in.tum.de/Par/arch/usb/usbdoc/ - Linux USB device driver
http://www.microsoft.com/technet/archive/wce/support/usbce.mspx
-AD
I've used an earlier edition of USB Complete by Jan Axelson. Indeed very complete.
From the editorial review:
Now in its fourth edition, this developer's guide to the Universal Serial Bus (USB) interface covers all aspects of project development, such as hardware design, device firmware, and host application software.
I'm curious, why did you pick the 9S12? I used it at a previous job, and was not pleased.
It had lousy gcc support so we used Metrowerks
which may have been okay for C, but often generated buggy C++
had a lousy IDE with binary project files!
The 9s12 was also slow, a lot of instructions executed in 5 cycles.
Not very power efficient, either.
no barrel shifter, made operations that are common in embedded code slow
not that cheap.
About the only thing I dislike more is an 8051. I'm using an ARM CortexM3 at my current job, it's better than a 9S12 in every way (faster clock, more work done per clock, less power consumption, cheaper, good gcc support, 32-bit vs. 16-bit).
I don't know which hardware you're planning to use but assuming that's flexible, STMicro offers a line of microcontrollers with USB/SPI support and a library of C-code that can be used with their parts. -- I've used their ARM7 series micros for years with great success.
Here is an excellent site maintained by Jonathan Valvano, a professor at the University of Texas. He teaches four courses over there (three undergraduate, one graduate), all are about using a 9S12 microcontroller. His site contains all the lecture notes, lab manuals, and more importantly, starter files, that he uses for all his classes.
The website looks like it's from the 90's, but just dig around a bit and you should find everything you need.
users.ece.utexas.edu/~valvano/
Consider AVR for your next MCU project because of it's wonderful LUFA and V-USB libraries.
I'm working on a project using the Atmel V71. The processor is very powerful and among lot's of high end connectivity offered on chip is a USB engine that will do device or host modes for 480 Mhz or 48Mhz (not USB 3.0). The tools are free and come with a number of host and device USB example projects with all the USB stack code right there. It supports 10 end points and all the transfers are done via DMA so you have most of the processor horsepower available for other tasks. The Atmel USB stack works without needing an RTOS
I'm planning to build a USB device that has buttons that some software needs to respond to, and indicators that the software needs to control. I'm new to USB, so I'm looking for any pointers that will get me started.
When I did some USB development a while ago, I found the information at USB Central extremely valuable.
For low bandwidth requirements, you can use something like the FT232R which is a single-chip USB serial implementation. The FTDI drivers are readily available and make the device appear as a regular serial port to the host computer. This is orders of magnitude easier than rolling your own USB implementation (for either end!).
Kinda vague, but in the past I've done a little bit of USB development. The easiest stuff tends to be HID related device as the subset of USB used to commincate is very to implement on both sides. There are hardware devices which are essentially stubbed out to work with HID, you just customize some circuity and go.
The USB standard is actually quite readable. Though it might be a bit overkill if you just want to create a simple device. You could probably get something like this, which is basically an 8051 controller with a USB connector together with firmware and a DLL.
Checkout WinDriver, which is a commercial multiplatform tool what give you easy way to implement usb drivers in user mode, source code compatible between Linux and Windows.