Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [usb-device]

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

647 questions
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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?
200ok404notfound
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Why put a 10k resistor between VUSB and GND?

I recently came across Yet Another RP2040 Trinket (the Beetle RP2040.) In their linked schematic something caught my attention: It is R10 below - a 10k resistor straight between VUSB and GND. I can't come up with a reason why you'd want it to be…
tylerl
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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 you be the device?" Can one device acts as a host…
Kozlov
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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 for the device to tell the host that it is…
kbro
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3 answers

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. This additional circuit has a capacitance of…
ibiza
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2 answers

How do I make the Fairchild FSA9280/FSA9480/FSA880 BOOT pin trigger? (Samsung Galaxy S)

this is a bit of a long shot but I'm hoping someone has access to the full data sheet for one of the chips listed in the title, and can tell me what combination of VBUS_IN and resistors on ID_CON will make it trigger the BOOT pin on the chip.…
TheBeano
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6 answers

USB B, mini B, or micro B for product design

I'm trying to decide which connector I should use for a USB peripheral I'm designing. Is there a guide for choosing one? The device is a portable electronic scoreboard that's 16"x10"x1". It will be outside, possibly in wet conditions. It will not…
Bob Baddeley
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Where exactly is the USB spec that explains what to do when the cable is first connected?

So I know about the USB 2.0 spec located at the USB.org site. I am a little lazy and impatient. Can someone tell me where to go to find out exactly what is expected of my peripheral device when the USB cable is connected? For example, if my…
robert bristow-johnson
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How can V-USB screw up the built-in SPI of an ATmega328p?

I'm working on a V-USB project that shows up as a Keyboard using an ATmega328p. The USB part is working great (it's not my first V-USB project), but after I start the V-USB stack with usbInit(), all calls to the SD card library fail. If I call the…
dnet
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RS232 vs USB CDC quality of service / should messages contain a checksum?

Does USB have a quality of service guarantee for data sent between my USB-CDC device and the USB host? I know with traditional RS232 in a noisy situation (e.g. automotive diagnostic port) bad bits happen often enough that checksums are important to…
Steven T. Snyder
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What is a product ID in USB and do I need to buy it for my project?

I am trying to develop a portable device that will allow me to transfer data from one USB storage device to another without a using PC/Laptop. I was reading the developers guide by Jan Axelson where I came across a section that said that one must…
Infusion of Wormwood n Asfodel
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Stability of USB +5V output

So i am designing a device that is supposed to connect to the PC via USB and draw power from the VBUS (+5v) of the USB. I am wondering if I need to put a voltage regulator in between the +5v from the USB and the microcontroller on my device. I've…
umps
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USB device with 2 ports - how to protect against user plugging in both

I've got a Full speed USB device which I want to provide 2 ports for - one each on opposite ends of the enclosure. This is so the cable can be connected wherever is most convenient. My MCU (atmega32u4) has only one interface, so the physical ports…
monty
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5 answers

Protecting a laptop from USB connected devices

In the past couple of months I've managed to destroy 2 perfectly good laptops through programming development electronics through USB. I've been wondering what could be done to prevent this. A couple of ideas I've had (not sure how practical): USB…
andowt
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Is a valid USB VID/PID necessary for strictly embedded use of the Bus?

So the system of USB VID/PIDs as far as I understand it is to avoid conflicts between devices and the USB-IF is handling the distribution of these IDs and wants a fee if you need a VID and a corresponding PID block. Now how is the situation looking…
timonsku
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