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product:usb2ax:specs [2013/04/01 05:36] xevel [USB2AX: Technical Specifications] |
product:usb2ax:specs [2013/04/01 06:06] xevel |
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The hardware of the USB2AX is relatively simple: only 17 components and a 16x20mm PCB. | The hardware of the USB2AX is relatively simple: only 17 components and a 16x20mm PCB. | ||
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+ | {{product:usb2ax:USB2AXv31_front_euro_s.jpg}} | ||
At its core is an ATMega32u2, an USB-enabled 8bit MCU with 32KB of FLASH, 2.5KB of RAM and 1KB of EEPROM, running at 16MHz. | At its core is an ATMega32u2, an USB-enabled 8bit MCU with 32KB of FLASH, 2.5KB of RAM and 1KB of EEPROM, running at 16MHz. | ||
- | The USB2AX v3.1 has a double LED (Red/Green), ESD protection on both connectors (USB and serial), breakout pads for RST, GND, HWB and the 4 SPI pins (PB0 to PB3). | + | The USB2AX v3.1 has a double LED (Red/Green), ESD protection on both connectors (USB and serial), 0.1" breakout pads for RST, GND, HWB and the 4 SPI pins (PB0 to PB3). |
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+ | To achieve Half-duplex operation on DATA, TX and RX are shorted together and the firmware alternatively turns ON the transmission or reception side of the MCU's UART. This is inspired by the [[http://www.vanadiumlabs.com/arbotix.html|Arbotix]]. | ||
==== Schematics ==== | ==== Schematics ==== | ||
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[[https://paranoidstudio.assembla.com/code/paranoidstudio/git/nodes/master/usb2ax/elec|All Eagle files]] | [[https://paranoidstudio.assembla.com/code/paranoidstudio/git/nodes/master/usb2ax/elec|All Eagle files]] | ||
- | The protection circuitry for TX and RX comes from the [[http://ruggedcircuits.com/html/ruggeduino.html|Ruggeduino]], and makes it possible to withstand applying 12V to DATA indefinitely, which can easily happen in real life with a shoddy custom cable, or a damage cable. | + | The protection circuitry for DATA, with the zener diode and PTC resistor, comes from the [[http://ruggedcircuits.com/html/ruggeduino.html|Ruggeduino]], and makes it possible to withstand applying 12V to DATA indefinitely. More detailed explanation of how it works [[http://forums.trossenrobotics.com/showthread.php?5675-USB2AX-v3.1&p=53101#post53101|here]]. This situation can easily happen in real life with a shoddy custom or damaged cable, and improper protection could result in a fried motherboard... |
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==== Mechanical ==== | ==== Mechanical ==== | ||
- | Size: 16mm x 36mm x 7mm (without heat-shrink tubing) | + | Size: 16mm x 36mm x ~7mm (without heat-shrink tubing) |
[[http://www.xevel.fr/other/usb2ax_v3.1.stl|3D CAD file (stl)]] | [[http://www.xevel.fr/other/usb2ax_v3.1.stl|3D CAD file (stl)]] | ||