Computing stuff tied to the physical world

Meet the Slave Plug

In AVR, Hardware on Nov 12, 2011 at 00:01

While fooling around with the ATtiny85 for the first AC current measurement tests, I found that ATtiny85 to be a pretty neat little chip in and by itself.

So why not create a plug for it, eh? Here’s the new Slave Plug:

DSC 2707

It’s all through-hole, so that it’s easy to assemble and easy to replace the ATtiny85 (or other compatible unit).

There are just enough pins to act as a (daisy-chainable) I2C slave and to drive a 6-pin header with 3..4 I/O pins:

Screen Shot 2011 11 08 at 23 14 11

With some care, that header can be made compatible with JeeNode ports, which means that this plug could even be used to act as host for another plug. Sort of an offloaded task for the “main” JeeNode. Or perhaps stand-alone, just to drive that single plug. Note also that the ATtiny85 supports differential ADC and an optional 20x gain stage, so that full scale voltages down to ≈ 55 mV can be measured (using the internal 1.1V bandgap as reference).

Here’s the schematic:

Screen Shot 2011 11 08 at 23 12 50

Pin 1 of the side header can be tied to either PWR (to create a port) or to the ATtiny’s RESET (SJ1).

And the port’s IRQ pin can optionally be connected to the ATtiny’s RESET pin via a solder jumper (SJ2).

Using a fuse setting, the ATtiny’s RESET pin can be turned into an I/O pin, but this means you’ll need a high-voltage programmer to re-flash the chip and lose the normal ISP programmability.

I’ll add it to the shop shortly, along with the other new boards.

It’s called v2, because there has been an (SMD) Slave Plug before, but that never made it into the real world.

  1. Tips for coding small simple programs for the tiny 45/85 using the arduino-IDE and a arduino as programmer.

    http://hlt.media.mit.edu/?p=1229

    The following Arduino commands should be supported:

    pinMode()
digitalWrite()
digitalRead()
analogRead()
analogWrite()
shiftOut()
pulseIn()
millis()
micros()
delay()
delayMicroseconds()

    And there is a SPI lib

    B Mathias Johansson 12 November 2011 at 10am

    • Nice library. Is the digitalWrite/Read code really stripped down for size and speed? I ask as the original Arduino port I/O is incredibly slow and well, huge! I tend to go straight for port bit banging these days.

      TankSlappa 12 November 2011 at 5pm

  2. Just a thought – how about using this slave board as Power Consumption Tracker v2? With differential inputs, this board should even be able to measure its own power consumption ;-)

    Tis the dark season, so more time for Jeexperimentation in the upcoming months…

    Ed Voncken 12 November 2011 at 12pm

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