Do I need FAT on both ends of a USB link? - usb

I have a product consisting of two boxes, both running an RTOS (not picked yet, say FreeRTOS):
Box A will have:
an SD card and a FAT stack
an "external" USB device port with MSD to allow PC access to the SD card
"internal" USB device port to Box B with MSD
Box B
an "internal" USB host port to Box A with MSD
QUESTION: do I need a FAT stack in Box B to be able to access the SD card in Box A?
I realize this is a very basic question but I have not been able to find the answer anywhere.
Thank you

As it turns out you do not need FAT on both ends. You need it at the Host end not the Device end. MSD takes over the SD Card at a low level so the file system is actually on the Host side. The way to access storage being managed at the Device end is to use MTP instead of MSD.

Related

Read Data Across USB Port

I'm playing around with an old Trackball I purchased from Sparkfun. My trackball powers on, but it doesn't actually work. All the lights flash, and it indicates that I've left and right clicked, but the mouse on my screen does nothing.
I want to monitor the input values of the trackball across a USB port so I can track down the problem. I've looked for code I can run on Netbeans, but came up empty handed.
Please advise
You didn't specified what OS are you using. You need dedicated driver for this device. In case of Linux you would need to write your own driver for the kernel. But first you need to have specification of protocol which this device is using over usb and also usb protocol itself. It is quite sophisticated task to do...
In case of Windows there are some programs for dumping transmission between usb host (PC) and device (trackball), but at the moment I can't give you any name of such program. In case of Linux you can dump the transmission using tcpdump or wireshark commands.

USB port to detect "close" or "open" switch

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

Zebra ZM400 USB Printing in WINCE 5.0 and VB.NET

I have an application in VB.NET, for smart devices, that prints labels containing some product information such as manufacturar name, product name, product weight and a barcode with the product name. In the past I used to print it using the serial port of my device but, due to a hardware change, the new device my company bought doesn't have the serial port anymore, but it has more USB ports than the old device.
I googled for answers but most of them didn't point me to an answer, due to most, or all of them, don't use the .NET CF to print in Zebras. Many of topics I found explain how to create a connection to USB port but, obviously, when moved to WIN CE, it didn't work.
I have the code for Zebra printing (ZPL II), just need a way to send it to one of my USB ports and check if it's printing the correct information.
Thanks in advance.
You need a driver for the printer. Windows CE provide a generic USB print transport driver that should work with many of those text-based printers, you may add it to your Windows CE OS image and try it.
If it works you may be able to send data to the printer by using PRN*: instead of COM*: as device name (PRN1:, PRN2: etc.).

Choosing a GPS to read position from VB.net 2010? Which one I should buy?

I'm trying to build a device to read the current GPS coordinates. The device will include a small computer inside running Windows 7.
I'm looking for a usb GPS to connect it to the computer and be able to read the GPS coordinates from my VB.net 2010 program. Of course, here the most important thing is what hardware I need to accomplish that. Suggest me some GPS models.
Do I need only a GPS receptor or do I need even more hardware?
In addition to jcibar's answer:
For Bluetooth GPS or most USB devices you probably don't even have to set the classic RS232 communication settings like "baud rate". It will just work, whatever baud rate you set.
Look at the "Ports (COM & LPT)" list of the Windows Device Manager - One of the "COM" devices listed should be the GPS receiver and it many times includes a description that indicates what it is.
E.g. on my Win7 x64 notebook I have a "Sierra Wireless Gobi 2000 HS-USB NMEA 9001 (COM8)" port, which is the notebook's built-in GPS. It will just start communicating the moment I open the port:
17.09.2013 10:12:01.890 [RX] - $GPGSA,A,1,,,,,,,,,,,,,,,*1E<CR><LF>
$GPGSV,4,1,16,10,,,,21,,,,20,,,,32,,,*7A<CR><LF>
$GPGSV,4,2,16,31,,,,30,,,,29,,,,28,,,*78<CR><LF>
$GPGSV,4,3,16,27,,,,26,,,,25,,,,24,,,*79<CR><LF>
$GPGSV,4,4,16,23,,,,22,,,,19,,,,18,,,*7E<CR><LF>
$GPGGA,,,,,,0,,,,,,,,*66<CR><LF>
$PQXFI,,,,,,,,,,*56<CR><LF>
$GPVTG,,T,,M,,N,,K,N*2C<CR><LF>
$GPRMC,,V,,,,,,,,,,N*53<CR><LF>
You can use any serial COM port / RS232 logger to test this.
You can use any GPS (USB, Bluetooth) that provides a RS232-level serial interface (serial port). The GPS will create a virtual serial port (e.g. COM13) that you can use in your VB.net program to read serial data (NMEA frames tipically at 4800 bauds).
For instance, for USB you could use something like this: Haicom HI-206USB.

Accessing specific USB ports for VB.net

New to VB.NET here.
I was wondering if there is a way to determine if there is something connected to a specific USB port. For example, I noticed that in the Device Manager under Universal Serial Bus controllers, there are Generic USB Hubs. For one of them, the Location is Port_#0001.Hub_#0003.
For what I am doing, I just want to know if something is connected to that specific USB port. It doesn't matter if it is a flash drive, USB HID, or even a microcontroller.
Thanks