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Questions tagged [usb-device]

Quesions about the design of USB devices that connect to a USB host, such as a PC.

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84
votes
10answers
146k views

How to get more than 100mA from a USB port

I heard that the current limit for a USB port is 100mA. However, I also heard that some devices can get up to 1.8A from a port. How do you get past the 100mA limit?
6
votes
1answer
12k views

switch between battery and usb power no microcontroller circuit

Following an earlier question about how to switch between battery and USB power, I would love to implement the TC2014 LDO as suggested by Russell McMahon. That way I could switch between 4AA ...
4
votes
3answers
4k views

Structure of a usb 2.0 connector [duplicate]

What is the role of the outer metal connector? (the one with two square holes) Does it have a potential? Is it insulated from the 4 pins? Are the 4 pins insulated from each other?
16
votes
2answers
10k views

Does a self-powered USB device have to connect to VCC from the host port?

A self-powered USB peripheral provides its own power, so is it okay to connect just D+, D- and GND to the host port, or do you always have to connect +5V as well, then wait for the negotiation phase ...
19
votes
3answers
15k views

How to limit inrush current?

I'm designing a device powered from USB. The device uses FTDI FT2232 chip for USB connection. Upon a command from a computer FT2232 chip should enable power via a MOSFET switch to rest of the circuit. ...
5
votes
1answer
2k views

USB composite device driver

I am wondering if it possible to create a USB device (in following the device) composed from a custom circuit (eg arduino) and ...
2
votes
1answer
81 views

Can I use the USB 2.0 and 3.x channels simultaneously in a USB 3.x port?

I am designing an FPGA development board for myself. I want a moderately high speed link (400-500MB/s) to the host PC and I'm considering several options, including an FTDI FT-60x bridge IC. The ...
1
vote
3answers
9k views

Supply power to USB with external power supply

I have a device (pyro-electric array detector) that connects to the Pc vis a usb. The device itself has an additonal power supply as well. Now a strange thing happens: If I connect the device to a Pc-...
0
votes
1answer
75 views

How do I build a USB joystick/button encoder board without using an Arduino or Teensy [closed]

I am making a macro keys button box and need something to convert the buttons into keyboard inputs on a PC, such as a shortcut key in a game. Previously I have used an Arduino Pro Micro, although in ...
20
votes
2answers
73k views

What exactly are the differences between a USB host and device

Came across some doubts: What exactly are the differences between a USB host and device? Is it just that who powers the bus? When two devices connect how the device say "hey I will be the host and ...
5
votes
6answers
2k views

Need a device that can take single input and covert to a keyboard key press on USB

Let me explain what I'm doing currently. We have made a finger heart rate monitor, each time your heart pulses a transistor is switched on via its base. The collector and emitter of the transistor ...
5
votes
3answers
3k views

Switch two USB ports via relay

I hava a tablet where I plug a PCB (with a microcontroller) on it. Because the tablet has only one USB port I have to connent and disconnect all the time the PCB, bacause I have to connect the ...
4
votes
2answers
1k views

Power a circuit off USB the correct way

I'd like to properly power a gadget off USB (2.4A USB powerbank https://www.amazon.com/Anker-20100mAh-Portable-Charger-PowerCore/dp/B00X5RV14Y/ref=sr_1_3?ie=UTF8&qid=1512261941&sr=8-3) ...
2
votes
2answers
4k views

Problems trying to wire a USB-C cable

I have been trying to figure out how to custom wire a USB-C to USB-A cable for a while, with no luck.I have tried some different connectors, but wanted to get some outside ideas on what I might be ...
1
vote
3answers
21k views

FT232R eeprom problem .. how to make PC recognize it

it's my first time to use FT232R .. when i connected it to the USB for the first time .. my Windows recognized it well, and its drivers were successfully installed .. and even after programming it ...
3
votes
2answers
2k views

USB data transfer without charge

This is a total hardware noob question, but I really need an answer to this one: I have 2 devices, A & B that are both self-powered. I would like to disable the +5VDC cord inside USB port, but ...
2
votes
1answer
3k views

How can I communicate between micro-controller and PC without the use of RS232/USB Adapter?

I use an NXP micro-controller, P89V51RD2, and use a RS232 to USB converter to program it. I'd like to communicate with the computer to send data but without using the RS232 adapter and convert serial ...
1
vote
4answers
578 views

Which TWO wires to disconnect to disable USB mouse

As there is more choice in DPDT switches than there is for 4PDT switches I am wondering which TWO connections are the best to disconnect to disable a USB mouse? I need an easy to use switch that ...
0
votes
2answers
279 views

USB-C as a high current power source

I'd like to power up a PCB that I'm design with USB-C. The main reasoning is that the connector is low-profile, reversible and can carry 5A at 5V. This PCB will have an ATmega2560 chip onboard, which ...
4
votes
2answers
2k views

Arduino programming on Uno fails using USB download on Windows 2000

I have a number of W2K systems that we are trying to use to program the new Arduino Uno and Mega devices. These boards now come with a USB connection, an upgrade from the prior FTDI. I'm not able to ...
3
votes
3answers
484 views

What is the source of this shape on my USB eye diagram?

I have designed a USB device around an STM32F105. It is USB 2.0 Full Speed CDC device configured as a Virtual COM Port using ST's USB Library. It uses the STM32's built-in PHY, and runs at 12 Mbps. ...
2
votes
1answer
2k views

FTDI chip (FT2232D) malfunction

I'd designed a USB-JTAG Programmer with FT2232D. I programmed Xilinx spartan3 FPGA 2 times yesterday and everything was perfect. But today when I connect it to my laptop I see the following message: "...
2
votes
0answers
205 views

Interfacing NAND flash with USBMSD

I'm trying to read files from a NAND flash (K9LAG08U0M) that I took off an old MP3 player, so far I've been able to read the NAND contents successfully by interfacing it to my PC as a USBMSD (Mass ...
2
votes
1answer
1k views

Pin of micro USB connector in Smartphone

The image below shows a Micro USB connector in a smartphone. I understand what the first 5 pins of the USB are i.e. USB_DM, USB_DP, USB_ID , VBUS and GND. The pin S1 is connected to VBAT (battery ...
1
vote
0answers
238 views

Atmel ARM, USB, and an SD Card as a MSD?

I'm currently trying to run the SAM L21 as both a CDC and an MSD over USB. Thankfully there is example code here to get me started. I can move files into the on-board ram just like any other storage ...
1
vote
3answers
3k views

Will cutting the data lines of USB still let the power to go through?

I am trying to Charge a USB connected device through a computer without transferring data. An USB 2.0 cable should have 4 wires: Vcc, Data+, Data- and Ground. If I only cut the Data wires and let the ...
1
vote
2answers
1k views

What type of USB Protocol for Datalogger

I am attempting to create a USB datalogger and would like to first start with creating a program that transmits Hello World over USB not using some kind of CDC communication. I am trying to figure ...
1
vote
1answer
278 views

Does USB CDC always use a UART channel?

I'm working with an Atmel SAM4 ARM Cortex M4 microcontroller and every example I've seen using USB CDC mode bridges a UART channel, and it looks like checks the UART's registers to read the data. Is ...
1
vote
2answers
1k views

Can i connect Power source (like usb charger) parallel connection with power bank output for keep Uninterruptible power supply (UPS)

I have a question about uninterruptible power supply (do it yourself). I have a simple power bank and relay (or light) i want that my relay will be always on even the power adapter are disconnected. ...
1
vote
1answer
238 views

Simple Audio Sampler And Looper

I am seeking to build a small drum pad that can trigger short mp3 files. Here there are a lot of specifications and I don't expect to have everything explained, but any tips on how to go about making ...
0
votes
1answer
4k views

USB-C cable layout

I want to hook up something to a usb-c cable, only for power. See it as lighting a LED with usb-c. However, once I cut the wire, I was surprised. I found a twisted pair (green, white) a yellow wire (I ...
0
votes
2answers
390 views

Do I need an OS in my device?

I am planning to build a device that will help transfer data from one USB storage device to another.I am planning to incorporate a touch screen interface to provide the user with more control over ...
0
votes
1answer
390 views

MCP2200 - which GPIOs for DTR, DCD, DSR and RI?

Due to the recent controversy surrounding FTDI, I'm looking for a replacement for future designs. I'm looking very hard at the MCP2200. The only thing I can't figure out is that they have several GPIO ...
0
votes
3answers
5k views

Modifying USB Battery (Portable Power Banks) to charge while charging (to use as ups)

I've been checking all the questions and can find many similar ones, but unfortunately none that addresses my problem. I ended up reading many interesting questions and answers (including e.g. this ...