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I am supposed to provide in my circuit, multiple analogue inputs (max 5V) to (multiple) amplifiers and I am planning to do it using micro-controller and external DACs. When I researched a little I came to find out that there are two ways of doing that (when using external DAC ICs interfaced with the micro-controller). One way is to use a single DAC IC with multi-channel outputs, and the other is to use multiple DAC ICs (one for each analogue signal required).

I have previously worked with ADCs, and never with DACs. I used two ADS8319 and interfaced them with my micro-controller using SPI-interface and 4-Wire CS Mode Without Busy Indicator (data sheet page number 22).

Now my question here is that if I want to use multiple (six to be exact) DACs for e.g this one DAC8560, am I capable of doing it using this DAC8560 ? The reason for asking this question is that in the DACs data sheet I cannot find any exemplary diagram which shows the usage of multiple DAC over SPI interface, neither its mentioned somewhere the usage of DAC8560 in multiple configuration (like it was mentioned in ADS8319's datasheet (page 22) ). One more question regarding this is that in ADS8319's data sheet its clearly shown the usage of 4-wire interface while using the SPI (as what I know about SPI is that it is 4 wire interface according to the WIKI as well), however in DACs datasheet, the IC clearly has 3 pins for the serial peripheral communication, which is confusing for me (whether it would support the usage of multiple ICs or not) as this 3 wire for SPI is new for me.

P.S I know using a single DAC with multiple channel outputs for e.g this one could be an easier solution to it, but I am not sure if doing that requires high programming skills (since I think I would be supposed to control DAC outputs on a single IC so I think that would require some kind of programming complexity and I am not sure if I am capable of doing that since I am not a good programmer). So can you please comment on that as well, whether using a multi-channeled output DAC requires some complex programming on the part of micro-controller (i would be using Arduino UNO) or not ?

Your kind replies and suggestions would be highly appreciated. Thankyou!

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  • \$\begingroup\$ "I am supposed to provide in my circuit, multiple analogue inputs" - do you mean outputs? DACs make analogue outputs. \$\endgroup\$ – Andy aka Nov 17 '16 at 14:47
  • \$\begingroup\$ yes, inputs as in inputs to the amplifier's, which would be the analogue outputs from DACs \$\endgroup\$ – yiipmann Nov 17 '16 at 15:02
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The reason most DACs and ADCs have a 3-wire SPI interface is because they are unidirectional devices; some ADCs may have a few registers that can be written to in order to control e.g. input gain, but at their heart ADCs are read-only and DACs are write-only. (Note that the 4-wire mode described in the ADS8319 datasheet is not 4-wire SPI, it is a 4-wire control scheme that only uses SPI on 3 of the pins, with the fourth acting as a form of latching signal.)

Multiple SPI devices on a single bus usually means multiple nSS signals. This is shown in figure 54 of the ADS8319 datasheet as already noted. These signals can either be tied directly to an output from the MCU/DSP/FPGA/etc. or they can be derived from a demux such as the 74HC138 in order to save pins. You may be able to daisy-chain devices as shown in figures 57 and 59 of same, but it should not be assumed that any given device supports this.

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