tomu-hardware
github.com / im-tomu
A tiny ARM microprocessor which fits in your USB port.

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ReferencesQtyDescriptionManufacturerMPNManufacturerMPNManufacturerMPNDigikeyMouserRSNewarkFarnell
R3 R42RES SMD 15 OHM 1% 1/16W 0402YAGEO (VA)RC0402FR-0715RL311-15LRCT-ND603RC0402FR0715RL678880026M67829239014
U11IC MCU 32BIT 64KB FLASH 24QFNSILICON LABORATORIES INCEFM32HG309F64G-B-QFN24SILICON LABORATORIES INCEFM32HG309F64G-A-QFN24336-3896-ND634HG309F64GBQFN24872710447Y07792475985
C1 C22CAP CER 1uF 10V X5R 0402AVX CORPORATION (VA)0402ZD105KAT2ATaiyo YudenTMK105BJ105MV-FMurataGRM155R61A105ME15D587-3245-1-ND963TMK105BJ105MVF814523706M40411740588
C31CAP CER 4.7uF 6.3V X5R 0402MURATA ELECTRONICS (VA)GRM155R60J475ME47DTaiyo YudenJMK105BBJ475MV-F587-2787-6-ND963JMK105BBJ475MVF814523068X27802426952
D11LED GREEN CLEAR 0402 SMDKINGBRIGHT COMPANY LLC (VA)APG1005VGC-T-5MAV754-1815-1-ND604APG1005VGCT5MAV124687423X47942062324
R1 R22RES SMD 52.3 OHM 1% 1/16W 0402YAGEO (VA)RC0402FR-0752R3LYAG3180CT-ND603RC0402FR0752R3L701444490W39292140645
D21LED RED 0402 SMDPANASONIC ELECTRONIC COMPONENTS (VA)LNJ247W82RALNJ247W82RACT-ND667LNJ247W82RA787020766W24252112119

Tomu HArdware

I'm Tomu a tiny ARM microprocessor which fits in your USB port. I have two buttons and two LEDs.

We're available on mailing lists and IRC:

Built out of a 3D printed part + 2 layer "thin" PCB. LCA2018 and Crowd Supply boards are 0.6mm.

Designs and documentation are available in:

  • pcb/: KiCad design files
  • docs/: PDF schematics, pin-out diagrams, and 3D renders

The board requirements are very lo-fi:

  • 6mil traces
  • 6mil clearance
  • 0.3mm drill / 0.6mm vias

The primary MCU is a Silicon Labs EFM32HG309 (datasheet, reference manual).

The important features are:

These make something which is almost hand solder-able fit into the tiny size.

All parts are available from Digikey, and are readily available from other suppliers.

  • Resistors
    • 2 x 0402 - 15 Ohm - Digikey
    • 2 x 0402 - ~50 Ohm (Depends on LED choice)
  • Capacitors - Digikey Capacitors 0402, >1uF
    • 2 x Capacitor 1uF 0402
    • 1 x Capacitor >10uF 0402
  • 2 x LED 0402
  • 1 x EFM32HG309 or EMF32HG308

The PCB is thinner than a USB socket, and has exposed contacts on the reverse side, so it needs a case in order to make proper contact with the USB pins, and to not short on the shield of the USB port.

Early prototypes used a business card that had been folded over, however the crowd funding campaign made enough to cut steel and make a case.

Designs are available in the case/ directory. Cases for earlier board versions tend to require higher tolerance on 3D printers.

The aim was to prove that a device which fits in your USB port could be createdby hobbyists in small quantities extremely cheaply.

TOMU comes from the abbreviation "Tim's Open Micro USB".

What ever you want! If you do create something, please send me the info!

The contents of this repository excluding third_partydirectory is released under your choice of the following two licences: