Arduino Forum

Products => Arduino Due => Topic started by: prasimix on Nov 21, 2016, 06:38 pm

Title: How to avoid power-up 10ms HIGH on DAC0 and DAC1 pins on DUE?
Post by: prasimix on Nov 21, 2016, 06:38 pm
I'd like to have LOW (0 V) on both DAC0 and DAC1 outputs predicatable on each power on. I can measure 10 ms HIGH on both output (see attached picture for one output) and wondering is it possible to avoid that somehow?

Many thanks in advance.
Title: Re: How to avoid power-up 10ms HIGH on DAC0 and DAC1 pins on DUE?
Post by: ard_newbie on Nov 22, 2016, 06:54 am

I suggest that you bypass your builtin DACs since you can't have 0V as per sam3x datasheet.

Instead connect one or more DAC MCP4922 in SPI mode, see : http://schianorobotics.altervista.org/Arduino_DUE___DAC_MCP4922.pdf
Title: Re: How to avoid power-up 10ms HIGH on DAC0 and DAC1 pins on DUE?
Post by: prasimix on Nov 22, 2016, 03:28 pm
Thanks for your suggestion. It seems that is easier to forget DAC outputs and deploy a dedicated device since for expanding output levels to go down to zero at least one op-amp is required anyway. I found MCP4822 (https://www.microchip.com/wwwproducts/en/MCP4822) particularly interesting since it has internal reference and it's dual channel with SPI.

Making some further test I found that actually other pins are also set to high for the first 10 ms after power is applied. I thought that is maybe connected with reset (yellow trace) but it's not. See attached picture for the PIN10 (magenta) that is not initiated after power on (cyan). Any idea why is that? Maybe I should open a topic with new title.