alfred v2 schematics

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1

I’ve been working on a custom board to replace the current alfred/alfie
boards
we’re using on the RPi.

The improvements include:

  • Feedback from door activation
  • Filtered and buffered communications to the
  • In-Circuit reprogramming of the AVR
  • Optically isolated bell input
  • Fits nicely over a RPi

Schematics attached, board is mostly layed out now. Any feedback welcome

Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

alfred_v2_r1.pdf (46.2 KB)

2

Looks ace :smiley: . Few thoughts:

  1. Breaking out the extra pins / ADCs for extra sensoring would be good.
    I normally use servo-style connectors for this, (signal, +5v, gnd). I
    know Jim has a shutter sensor in the works that we’ll need an analog input
    for.
  2. Should there be a battery backup for the RTC?
  3. Can we put an i2c accelerometer / gyro on there? See who has closed
    / opened the door the fastest (obviously only for the inner door)
  4. I cant see a connector for an ‘open door’ button as we have on ALVIN.
    Might be a use for the headers mentioned in #1
  5. Can we have an FTDI pinout header on there somewhere for testing
    serial without the pi?On 7 April 2014 11:57, Ben Dooks bjdooks@googlemail.com wrote:

I’ve been working on a custom board to replace the current alfred/alfie
boards
we’re using on the RPi.

The improvements include:

  • Feedback from door activation
  • Filtered and buffered communications to the
  • In-Circuit reprogramming of the AVR
  • Optically isolated bell input
  • Fits nicely over a RPi

Schematics attached, board is mostly layed out now. Any feedback welcome

–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

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3

Looks ace :smiley: . Few thoughts:

  1. Breaking out the extra pins / ADCs for extra sensoring would be
    good. I normally use servo-style connectors for this, (signal, +5v, gnd).
    I know Jim has a shutter sensor in the works that we’ll need an analog
    input for.

Do we really need analogue for an on/off style signal>

  1. Should there be a battery backup for the RTC?

I will see if this can be added.

  1. Can we put an i2c accelerometer / gyro on there? See who has
    closed / opened the door the fastest (obviously only for the inner door)

I will either have long pins to connect external one, or add some i2c pins
for an external one.

  1. I cant see a connector for an ‘open door’ button as we have on
    ALVIN. Might be a use for the headers mentioned in #1

I will look at bringing the unused IO pins out.

  1. Can we have an FTDI pinout header on there somewhere for testing
    serial without the pi?

For testing, it would be easy enough to build a test-rig on some strip
board with the necessary
bits. We’ll need 3.3V as well as 5V for it, so having a fixed reg and a
2x13 strip won’t be too
difficult to build.

Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

4

For RTC backup, would a coin-cell be ok, or should we put a little
rechargeable battery back on it?
I think battery backup for the RTC would be in the 1nA region.On 7 April 2014 12:28, Bob Clough parag0n@ivixor.net wrote:

Looks ace :smiley: . Few thoughts:

  1. Breaking out the extra pins / ADCs for extra sensoring would be
    good. I normally use servo-style connectors for this, (signal, +5v, gnd).
    I know Jim has a shutter sensor in the works that we’ll need an analog
    input for.
  2. Should there be a battery backup for the RTC?
  3. Can we put an i2c accelerometer / gyro on there? See who has
    closed / opened the door the fastest (obviously only for the inner door)
  4. I cant see a connector for an ‘open door’ button as we have on
    ALVIN. Might be a use for the headers mentioned in #1
  5. Can we have an FTDI pinout header on there somewhere for testing
    serial without the pi?

On 7 April 2014 11:57, Ben Dooks bjdooks@googlemail.com wrote:

I’ve been working on a custom board to replace the current alfred/alfie
boards
we’re using on the RPi.

The improvements include:

  • Feedback from door activation
  • Filtered and buffered communications to the
  • In-Circuit reprogramming of the AVR
  • Optically isolated bell input
  • Fits nicely over a RPi

Schematics attached, board is mostly layed out now. Any feedback welcome

–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

–
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Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

5

Breaking out the extra pins / ADCs for extra sensoring would be good. I
normally use servo-style connectors for this, (signal, +5v, gnd). I know
Jim has a shutter sensor in the works that we’ll need an analog input for.

Do we really need analogue for an on/off style signal>

Not once it’s properly calibrated and tested, but I do need an
analogue input until then.

I’m planning on connecting it to the RPi in the door with an SPI ADC
chip, so this particular version of the shutter sensor isn’t relevant
to ALFRED V2.

6

If I can get the board off this week, then we can use the v2 for both
ALFRED and ALFIE
replacements. It is up to you if you want to continue doing this.

PS, IIRC you may find the (minimus, irc) has a spare analogue comparator
input.On 7 April 2014 13:02, Jim MacArthur jim@mode7.co.uk wrote:

On 7 April 2014 12:40, Ben Dooks bjdooks@googlemail.com wrote:

Breaking out the extra pins / ADCs for extra sensoring would be good. I
normally use servo-style connectors for this, (signal, +5v, gnd). I
know

Jim has a shutter sensor in the works that we’ll need an analog input
for.

Do we really need analogue for an on/off style signal>

Not once it’s properly calibrated and tested, but I do need an
analogue input until then.

I’m planning on connecting it to the RPi in the door with an SPI ADC
chip, so this particular version of the shutter sensor isn’t relevant
to ALFRED V2.

–
You received this message because you are subscribed to the Google Groups
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Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

7

coin cell should outlast the door.On 7 April 2014 12:49, Ben Dooks bjdooks@googlemail.com wrote:

For RTC backup, would a coin-cell be ok, or should we put a little
rechargeable battery back on it?
I think battery backup for the RTC would be in the 1nA region.

On 7 April 2014 12:28, Bob Clough parag0n@ivixor.net wrote:

Looks ace :smiley: . Few thoughts:

  1. Breaking out the extra pins / ADCs for extra sensoring would be
    good. I normally use servo-style connectors for this, (signal, +5v, gnd).
    I know Jim has a shutter sensor in the works that we’ll need an analog
    input for.
  2. Should there be a battery backup for the RTC?
  3. Can we put an i2c accelerometer / gyro on there? See who has
    closed / opened the door the fastest (obviously only for the inner door)
  4. I cant see a connector for an ‘open door’ button as we have on
    ALVIN. Might be a use for the headers mentioned in #1
  5. Can we have an FTDI pinout header on there somewhere for testing
    serial without the pi?

On 7 April 2014 11:57, Ben Dooks bjdooks@googlemail.com wrote:

I’ve been working on a custom board to replace the current alfred/alfie
boards
we’re using on the RPi.

The improvements include:

  • Feedback from door activation
  • Filtered and buffered communications to the
  • In-Circuit reprogramming of the AVR
  • Optically isolated bell input
  • Fits nicely over a RPi

Schematics attached, board is mostly layed out now. Any feedback welcome

–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

–
You received this message because you are subscribed to the Google
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–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

–
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8

Connecting the shutter sensor to Alfie or the minimus both seem more
complicated than attaching it to the RPi. I only have to add code to
the RPi if I use an ADC chip.On 7 April 2014 13:11, Ben Dooks bjdooks@googlemail.com wrote:

If I can get the board off this week, then we can use the v2 for both ALFRED
and ALFIE
replacements. It is up to you if you want to continue doing this.

PS, IIRC you may find the (minimus, irc) has a spare analogue comparator
input.

On 7 April 2014 13:02, Jim MacArthur jim@mode7.co.uk wrote:

On 7 April 2014 12:40, Ben Dooks bjdooks@googlemail.com wrote:

Breaking out the extra pins / ADCs for extra sensoring would be good.
I
normally use servo-style connectors for this, (signal, +5v, gnd). I
know
Jim has a shutter sensor in the works that we’ll need an analog input
for.

Do we really need analogue for an on/off style signal>

Not once it’s properly calibrated and tested, but I do need an
analogue input until then.

I’m planning on connecting it to the RPi in the door with an SPI ADC
chip, so this particular version of the shutter sensor isn’t relevant
to ALFRED V2.

–
You received this message because you are subscribed to the Google Groups
"Hackspace Manchester" group.
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Visit this group at http://groups.google.com/group/hacman.
For more options, visit https://groups.google.com/d/optout.

–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

–
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9

If you are attaching the shutter sensor to the downstairs shutter, then that
will be handled by the new v2 alfred, and you won’t have the SPI bus to
access as it is being used elsewhere.

The V2 board will have a pair of ADC pins available. If we want to use the
"SPARE" line on the output, then I can have that connected to an ADC for
use in checking the shutter status.On 7 April 2014 13:28, Jim MacArthur jim@mode7.co.uk wrote:

Connecting the shutter sensor to Alfie or the minimus both seem more
complicated than attaching it to the RPi. I only have to add code to
the RPi if I use an ADC chip.

On 7 April 2014 13:11, Ben Dooks bjdooks@googlemail.com wrote:

If I can get the board off this week, then we can use the v2 for both
ALFRED
and ALFIE
replacements. It is up to you if you want to continue doing this.

PS, IIRC you may find the (minimus, irc) has a spare analogue comparator
input.

On 7 April 2014 13:02, Jim MacArthur jim@mode7.co.uk wrote:

On 7 April 2014 12:40, Ben Dooks bjdooks@googlemail.com wrote:

Breaking out the extra pins / ADCs for extra sensoring would be good.
I
normally use servo-style connectors for this, (signal, +5v, gnd). I
know
Jim has a shutter sensor in the works that we’ll need an analog input
for.

Do we really need analogue for an on/off style signal>

Not once it’s properly calibrated and tested, but I do need an
analogue input until then.

I’m planning on connecting it to the RPi in the door with an SPI ADC
chip, so this particular version of the shutter sensor isn’t relevant
to ALFRED V2.

–
You received this message because you are subscribed to the Google
Groups

“Hackspace Manchester” group.
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an

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–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com

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Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com