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wlan-slovenja currently develops an IO-shield for an cheap microcontroller development board


  • make a more detailed spec.
  • Send it to Musti
  • get a quote from Musti



  • must be able to power toggle minimum 6 devices
  • must be able to power toggle a minimum 6 Amps per channel
  • must give power consumption per port and in total via USB/serial
  • must be able to send commands to the device via USB/serial
  • must have a watchdog which autonomously power cycles the controller device (== a specific channel) which gets power cycled if the controller device does not “ping” the device anymore via USB/serial
  • the device must be able to run on USB power or via 15V-24V power supply.


  • log and monitor various sensor values:
    • humidity
    • voltage (MUST)
    • temperatur
    • lightning
  • have a second USB/serial interface.
  • support channels with 220V (but these must be electrically isolated from the other channels and from the device)
  • optionally the device should run on / support 48V PoE

managed poe switches/routers

maybe a nice, cheap and outofthe box useable solution for poweycling boards are managed poe switches

and a really cheap one (and infact a router not just a switch) is the mikrotik RB750UP

5port switch, switchable poe passthrough for 4 ports
maximal 500mA (24 bzw 28V) i.e. ~12W max. per device
current monitoring (but not really ready yet)
over-current shutoff (which might create problems with higher powered bootup draws)
1x usb
? poe switching useable with openwrt? infact the (RouterOS) poe-driver kernelmodule is tagged as gpl, but remember this is mikrotik )-;

btw. mikrotik has an switch with SwOS too that has controllable Poe ports, and in SwOS the current monitoring should already work!

ubiquity announced a similar productline too (THOUGH-Switch). FIXME Specifications?
There is a 5 port 24V or 8 port 24/48V version, and they might have no problem in powering/switching 20W boards (or at least an N2800MT should work)

  • Small version: 5(+1) $89, 24V, 400mhz mips32k, 64MB, 1x USB ports likely 800mA per port (as specification says 18W, and max 60W in total)
  • PRO version: 8(+1) $189, 24 or 48V, 400mhz mips32k, 64MB also only max 18W per port? (max 150W in total)

and there are real switches too for 50$, with 4 802.3af ports, but having 48V is likely no benefit for us (we would need 802.3af to passive poe adapters) (max 15.4W (~300mA) per port!)


just powercycle or more?

  • serial
  • network boot server
  • usb-storage client to allow booting from the recovery device

for a board to be useable as a storage device, to do an receover boot of the research device from it needs an client or OTG capable usb port, not “just” host ports.

other boards

nice: carambola 17-22€ 2xLAN, 2xCOM, USB, GPIO, (SPI), 320Mhz raMIPS, 32MB RAM, 8MB flash, 2mm pinheader, development board anaother 17-22€
the carrier has the lan physicals, i.e. outofthe box the small board can not do lan

a bit faster, atheros wifi, and likely more power efficient, and as complete router (ufl, 2xlan,usb,32mb ram, 8mb flash) even cheaper (36$): Alfa Hornet-UB Embedded Board Atheros AR9331

but gpio only available with unsolder/reuse led, caution there are 16/4 and 32/8 (RAM/Flash) variants!
similar:: [[|Alfa Network AIP-W502U PCBA]]

another ramips based openwrt board 35 GBP (mit stm32 expander (coudl act as storage device, lion chargen, gpio, onewire)): Omnima advanced automation systems same company offers also 220V switches, but expensive ones.

microcontroller managed relais

hw/recovery-device.txt · Last modified: 2012/07/17 22:32 by aaron