[TriEmbed] Chain-able EEPROM or Similar

Carl Nobile carl.nobile at gmail.com
Mon Nov 30 13:15:39 CST 2015


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?
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Triangle, NC Embedded Computing mailing list
>>> TriEmbed at triembed.org
>>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>>> TriEmbed web site: http://TriEmbed.org
>>>
>>>
>>
>
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>


-- 
-------------------------------------------------------------------------------
Carl J. Nobile (Software Engineer)
carl.nobile at gmail.com
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