Disable LDAC and CLR of a DAC

frekkia · May 29, 2022, 8:57pm

Hi guys, is there a way to disable the LDAC and CLR functions of the dac8562 so as to use it as a dac8552?

Thanks!

heke · May 29, 2022, 11:21pm

Tie the LDAC to GND and CLR to AVdd. Then the output is updated at SYNC edge.
(See page 4 on the datasheet).

Cheers,
Heke, AsamaLab

frekkia · May 30, 2022, 6:04am

Many thanks! I test it! not that I do not trust, but I searched and searched on the datasheet without finding anything, you could indicate me or make a screen where this is written

heke · May 30, 2022, 10:17am

Hi frekkia

The information is indeed not easy to spot from the datasheet.
Here’s the clip taken from page 4:

It is stating that if the LDAC is tied to GND, then the latch that is between the SPI block and DAC is transparent and DAC output is updated at SYNC edge.

It may be a good idea to test it yourself to confirm the desired operation.
TI’s FAE may also help you there.

Cheers,
Heke, AsamaLab

frekkia · June 2, 2022, 8:57am

Hi Heke, i test but not work with dac8562 im using this to substitute of dac8552 but i think is different dac

heke · June 2, 2022, 12:24pm

Hi frekkia,

Unfortunate to hear.
I think there are still things to try. Let’s make it work!
Allow me to ponder this a bit (it’s already late night this part of the world)… Meanwhile, I wonder, could you provide a bit more information:

What DAC value did you write to the chip and what output voltage you got (or actually, how the operation differs to 8552)?
Is there a chance to get a photo or schematics of the test circuit?

If the great people at Digi-Key have ideas, kindly give a shout.

Cheers,
Heke

frekkia · June 2, 2022, 1:39pm

Hi heke, this is the schematic https://mutable-instruments.net/modules/peaks/downloads/peaks_v30.pdf

heke · June 3, 2022, 12:30am

Hi frekkia,

Thank you for the schematics. It looks OK.

The register format for 8562 and 8552 is not 1:1. That is, 8552 cannot be controlled with the same software blob as 8562. I am afraid that you will need to write a new driver for the DAC.
Take a peek on example like this (Note: is for Arduino):

github.com

renatoianhez/DAC8552a/blob/master/DAC8552a.cpp

/*************************************************************************
** Library for Digital to Analogic Converters by Texas Instruments      **
** DAC8550, DAC8551, DAC8552, DAC8554, DAC8555 on Arduino.              **
** By Renato Ianhez                                                     **
*************************************************************************/
#include "DAC8552a.h"

DAC8552a::DAC8552a() {
}
void DAC8552a::setPins(int DIN, int SCK, int SYNC) {
	_DIN = DIN;
	_SCK = SCK;
	_SYNC = SYNC;
	pinMode(_DIN,OUTPUT);
	pinMode(_SCK,OUTPUT);
	pinMode(_SYNC,OUTPUT);
}

void DAC8552a::initializeDAC8552a() {
	Serial.begin(9600);

This file has been truncated. show original

Cheers,
heke

frekkia · June 3, 2022, 10:33am

Ah very hard for me, no have the competence for this, but i try.

I think i have to change this dac configuration:

github.com

matias-levy/peaks/blob/main/firmware/peaks/drivers/dac.cc

// Copyright 2013 Emilie Gillet.
//
// Author: Emilie Gillet (emilie.o.gillet@gmail.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

This file has been truncated. show original

And

github.com

matias-levy/peaks/blob/main/firmware/peaks/drivers/dac.h

// Copyright 2013 Emilie Gillet.
//
// Author: Emilie Gillet (emilie.o.gillet@gmail.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

This file has been truncated. show original

heke · June 3, 2022, 12:52pm

Hi frekkia,

First of all, my apologies for providing pointer to 8552 example code instead of 8652. My bad.
I’ll take a look into your code tomorrow morning. Meanwhile, encouraging everyone to provide a solution.

Cheers, heke.

heke · June 4, 2022, 12:01am

Hi frekkia,

OK. Took a look at the driver code.
I do not have STM32 SDK, thus cannot test the code.
However, attempted to modify the driver to suit for DAC8562, with the following remarks:

The code is not compiled nor tested. No guarantee given that it works.
Tried to make as few changes as possible.
The original code has methods Dac::Write and Dac::Update. Not sure how the author is using them.
The Write method does not test if SPI frame send is complete. Added a wait loop.
The Update method does not test if SPI frame send is complete. Did not include a test for frame overlap (yet).
There are 8 extra clocks in each DAC access due to 16 bit SPI frame (I’d use 8 bits frame instead…)
Due to external 2.5V reference, the DAC8562 needs to be configured to use that. Added code for it in Dac::Init(). Remove, if does not work.
Disabling LDAC pin functionality with a register write in Dac:Init(). Make sure LDAC pin is grounded!
Note: Channels are not updated synchronously, thus you may observe minor phase shift. Maybe does not matter as I guess they are oscillator outputs.

Let me know if this does not work or works only partially.

dac.cc (3.2 KB)
dac.h (2.6 KB)

Cheers, heke

frekkia · June 6, 2022, 11:52pm

Hi heke, i test tomorrow! Many many many thanks!

frekkia · June 10, 2022, 10:32am

Hi Heke, i test it, but not all work,now it seems more controllable, the sounds stand out better, but still not as they should, it seems that they are still digital and not completely analog

heke · June 10, 2022, 11:43pm

Hi frekkia,

Good to hear that you got something out.
It sounds like the output gets distorted.
According to the schematics, there is quite a lot of gain in the output stage.
In addition, it seems that the original DAC’s output range is from 0 to Vref, where as
in my code version the range is set 0 to 2xVref. I’ve attached below a modified version of the code
where the range is set to 0…Vref. Test with it and tell what you get.
dac.cc (3.3 KB)

Cheers, heke

frekkia · June 12, 2022, 4:38pm

Hi heke, i test, the out1 is ok, out2 have still distortion. This is a Module eurorack for Music an function of the out 2 is a Kick drum.

heke · June 13, 2022, 10:26am

Hi frekkia,

OK, so we’re almost there. I’ll look into the code.
Meanwhile, could you inform what kind of measurement instruments do you have at hand
(multimeter, oscilloscope?) and what SDK you are using to compile the code and flash the MCU?
BTW, modular synthesizer sounds fun.

Cheers, heke

frekkia · June 14, 2022, 11:33am

The tool chain is a arm-eabi with a oracle virtual box, look this: Mutable Instruments | Peaks

Yes im a oscilloscope and multimeter

Thanks heke.

heke · June 22, 2022, 12:12pm

Hi frekkia,

My apologies for late response due to busy times…

Could you try the code below.
dac.cc (2.9 KB)

If still getting distorted output, I wonder, could you take a picture of the oscilloscope display showing a typical signal? That would help to understand the source of the problem.

Cheers, heke