[Coco] Battery-Backed RTCs for CoCo?

[RETRO Innovations]

On 12/1/2018 12:50 AM, Dave Philipsen wrote:
> Yeah, in single quantities from Digi-Key it is a little expensive but 
> you can buy the whole module from China (eBay) for a buck or two. It 
> includes a NVRAM too.

I am surprised they can offer the module for $.74:

https://www.ebay.com/itm/1Pc-Arduino-DS3231-AT24C32-IIC-Module-Precision-RTC-Real-Time-Clock-Quare-Memory/132863210997?hash=item1eef43b5f5:g:NqwAAOSwmfhb9QKq:rk:3:pf:0

but Digikey is $4.80 even in 100s:

https://www.digikey.com/products/en/integrated-circuits-ics/clock-timing-real-time-clocks/690?FV=ffe002b2&quantity=100&ColumnSort=1000011&page=1&k=ds3231&pageSize=25&pkeyword=ds3231

And, while 400kHz is std I2C, as you note, it makes it tougher to 
interface, at least compared to SPI (about the same price) or parallel 
(more expensive)

Jim