[TriEmbed] Chain-able EEPROM or Similar

[Shane Trent]

Adam,

You could use an 8-pin ATTiny to as your 0th element in each array and have
the data in flow through but a command to the new 0th element would return
your string length. Bit-bang to match your desired protocol and you are
good to go. As a side note, here is a cool article where they measured the
power supply drop to determine the number of addressable LEDs on a string.
You would need a seperate data line for each string or to have ALL of the
LEDs in series but it is food for thought.

https://cpldcpu.wordpress.com/2014/11/16/ws2812_length/

Shane

On Mon, Nov 30, 2015 at 2:15 PM, Carl Nobile via TriEmbed <
triembed at triembed.org> wrote:

> Adam,
>
> The only thing I can think of that may work in your situation are 8 bit
> latching shift registers. Here are two links to PDF datasheets that could
> help.
>
> https://www.fairchildsemi.com/datasheets/MM/MM74HC595.pdf
>
> http://www.ti.com/lit/ds/symlink/sn74ls673.pdf
>
> ~Carl
>
> On Mon, Nov 30, 2015 at 2:08 PM, Adam Haile via TriEmbed <
> triembed at triembed.org> wrote:
>
>> Oh... yeah. Important part. The data in the chip needs to be non-volatile!
>> So, the data would be stored on each chip individually and then read
>> serially.
>>
>> On Mon, Nov 30, 2015 at 2:07 PM, Brian <triembed at undecidedgames.net>
>> wrote:
>>
>>> If you can spare three pins, shift registers are (maybe) exactly what
>>> you need.
>>>
>>> You didn't mention how the bytes get there to begin with, which does
>>> affect the answer.
>>>
>>> Most (?) serial-out shift registers support chaining out-of-the-box;
>>> they have a latch signal to preload their internal flip-flops as well as an
>>> external serial input.  By their very nature, the first (n) bits clocked
>>> out will be their own bits, followed by whatever bits clock in on the
>>> serial input.  Natural chaining.
>>>
>>> If you have parallel inputs that can all be latched at once, a single
>>> latch + clock-out + data-in is all you need on the host MCU.
>>>
>>> If the data comes into the registers serially, well, that's a bit more
>>> complicated.
>>>
>>> -B
>>>
>>>
>>> On 11/30/2015 1:35 PM, Adam Haile via TriEmbed wrote:
>>>
>>>> I have /no/ idea if this technically is something that exists, but I
>>>> have to imagine it's possible.
>>>>
>>>> I need a small, cheap (isn't it always?) chip that can store a few bytes
>>>> of data. Actually a single byte is all I need. And can be accessed kind
>>>> of like a shift register where I can query an unknown number of devices
>>>> int the chain and get, in order, the byte that each one stores.
>>>>
>>>> The intent here is  so that I can have multiple, pre-wired, sets of LEDs
>>>> with an arbitrary order and number of LEDs on each. This chip would
>>>> store the LED count for each pre-wired section. Without knowing anything
>>>> about the pre-wired sections, I need to be able to poll all these chips
>>>> and from that know how many pre-wired sections there are, how many LEDs
>>>> each has, and in what order. The data returned just needs to basically
>>>> look like: 48, 36, 24, 18 (4 sections with 48, 36, 24, 18 LEDs, in that
>>>> order).
>>>>
>>>> I assume it would use an SPI-like interface... not exactly since I can't
>>>> use chip selects. Since I would have an arbitrary number. A 2 wire
>>>> interface would be great. Is it possible to do something like this with
>>>> I2C? Basically, I know what I need, but don't know what to call it.
>>>>
>>>> Any thoughts?
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>
>>
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>>
>>
>
>
> --
>
> -------------------------------------------------------------------------------
> Carl J. Nobile (Software Engineer)
> carl.nobile at gmail.com
>
> -------------------------------------------------------------------------------
>
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>


-- 

A blog about some of my projects.  http://fettricks.blogspot.com/
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