Arduino mega pinout serial usb B series#

According to the datasheet, it will hold a 500mA current load without tripping, then there is a grey area between 500mA and 1A where it would probably take a few minutes to heat up. They list a Bourns part number of MF-MSMF050-2. The circuit stays open until you deenergize the circuit and allow the PTC to cool off (takes less than a second). If you’re powering your Arduino from the USB cable, and attempt to draw too much current, say by short circuiting your +5V connection straight to ground (oh the many ways I’ve done this), the current spike causes a sharp increase in temperature within the PTC, causing it to immediately open the circuit. This provides over-current protection from blowing up the USB host controller circuit in your computer. This is a Positive Temperature Coefficient (PTC) Resettable Fuse.

Arduino mega pinout serial usb B series#

In series with this connection, and before USBVCC goes anywhere else, there is a black box on the schematic, reference designator F1. The upshot is that there is a direct connection from the V BUS connection in the USB socket to both the MOSFET Drain and the 16U2 UVCC pin. Fortunately, I have a PCBGrip System that is like a circuit testing tinker toy. Testing this is a little difficult, because to be absolutely sure, we need to use a multimeter to verify a path from the V BUS pin of the USB socket, which is only accessible under the board, to Pin 31 of the 16U2, located on the top of the board, and has a ridiculously small pin pitch. You can see I drew my own bright red line on the schematic with a question mark, because it’s unclear if there is a direct connection there, or if the USBVCC goes off to the MOSFET first, before connecting to the 16U2. Connect the USB jack shield, the metal housing that surrounds it, in a safe way so that doesn’t zap you, or zap the circuit.Connect the USB Ground pin inside the USB jack to the UGND pin of the 16U2, pin 28.Connect the D+ pin inside the USB jack to the D+ pin of the 16U2, pin 29.Connect the D- pin inside the USB jack to the D- pin of the 16U2, pin 30.Bring the USBVCC connection from the USB Type B jack, listed as V BUS in the USB documentation, to both the MOSFET in the voltage management section, and to the UVCC pin, USB Voltage pin 31, of the ATMEGA16U2 (henceforth referred to as the “16U2”) microcontroller.To try to clean it up a bit, I’ve blanked out all the portions that don’t directly involve the USB subsystem, but even after having done that, and enlarged the view slightly, part names and reference designators still sit on top of each other and make it a little daunting. This is the official schematic covering the details of the Arduino USB connection. As before, we’ll take this step by step and part by part. Further, there are enigmatic symbols on there, like big black rectangles, that don’t really give you an immediate understanding of just what component was placed there, or what it’s purpose might be. There are a lot of things on the left hand side of the schematic, and they all seem to be crammed together tightly, so that the drawing doesn’t flow off the left side of the page. I would highly recommend grabbing a cup of coffee and a donut, because this is a longish post.īuild An Arduino UNO R3 from Scratch Table of ContentsĪ Confusing Arduino USB Connection Schematic We now leave the op-amps and power management behind and move into the Arduino USB connection that allows us to connect a computer to the Arduino to send and receive data. In Part 6, we covered the how and the why of the Pin 13 LED, along with the related op-amp that appears there.