[sdiy] nice Digi Pot

Tom Wiltshire tom at electricdruid.net
Mon Jun 27 23:19:50 CEST 2016


On 27 Jun 2016, at 21:17, rsdio at audiobanshee.com wrote:

> I don't see why you would want to run multiple 8-bit DPOT chips off a single, larger bit-depth word command.

You'd want to because it saves you using up multiple pins with "slave select" lines.

Most of the Microchip stuff (I've used the SRAMs, EEPROMs and the Digipots) seems to expect a slave select. This is ok for a few devices, but you can use up quite a few pins on slave selects if you've got a few different things connected up.

As long as the devices expect a command which is a whole number of bytes, there's no extra work in daisy chaining (and this is the case for several Microchip devices - they have unused bits in the command to make a full word, which is why the non-support for daisy chaining is slightly frustrating). You just stuff bytes out of the SPI port and the job is done. In fact, it's quicker/easier than having to switch slave select lines over every couple of bytes.

Tom




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