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Best Single Board Computer for Analog output

Hi All,

I have a Raspberry Pi with some python code that generates 3 different signals with a need to output as an analog signal.
I have just realized that the R-Pi has only one PWM output. The Odroid on the other hand has no PWM output at all. I think Arduinos have two analog outputs, but I can't install Linux on an Arduino so it is not suitable for my needs.

I wonder if anyone has some suggestion as to what could I do to output three analog signals from a Raspberry or an Odroid.

would 2 raspberry-pis do the trick ?

http://www.linuxquestions.org/questi...9/#post5712498

Quote:

Originally Posted by schneidz (Post 5749285)

would 2 raspberry-pis do the trick ?

At least three would be needed. I would prefer something more clean that I can do with an unique SBC.

you can buy an additional board for RPi to have more PWM output (I have 16).
But PWM is not analog output.
And you can find a lot about it on the net, for example: https://circuitdigest.com/microcontr...i-pwm-tutorial

Hi,

Welcome to LQ!

I suggest that you look at http://www.linuxquestions.org/questi...#faq_lqwelcome too help compose future responses to the forum.

Quote:

Originally Posted by Boniato (Post 5749281)

You could look at https://learn.adafruit.com/mcp4725-1...ry-pi/overview

Quote:

Already mastered Analog Inputs with the Pi, and looking for a new challenge? How about: How can I generate an analog output on the Pi?!

There are several ways you can accomplish this, but one of the easiest and most flexible is to use a dedicated IC called a Digital to Analog Convertor (or DAC). A DAC allows you to specify a numeric value (0..255 for an 8-bit DAC, 0..4095 for a 12-bit DAC, etc.), and the IC will output a voltage based on the supply voltage, and relative to that numeric value. For example, using a 12-bit DAC like the MCP4725 we'll be using here, setting the value to 2048 on a 3.3V system will results in ~1.65V output on the DAC.

This guide will show you everything you need to know to be able to generate precise analog outputs using your Pi and the MCP4725 12-Bit I2C DAC, from connecting everything up, to how to use our easy Python library.

Since you did not provide the resolution required for 8 bit or better then you can use a DAC that suits your requirements. I have used Adafruit hardware without issues so you can rely on a good product.

Hope this helps.
Have fun & enjoy!
:hattip:

Quote:

Originally Posted by onebuck (Post 5749384)

Hi,

Welcome to LQ!

I suggest that you look at http://www.linuxquestions.org/questi...#faq_lqwelcome too help compose future responses to the forum.

You could look at https://learn.adafruit.com/mcp4725-1...ry-pi/overview
Since you did not provide the resolution required for 8 bit or better then you can use a DAC that suits your requirements. I have used Adafruit hardware without issues so you can rely on a good product.

Hope this helps.
Have fun & enjoy!
:hattip:

Hi oneback and thanks for your suggestions.
I have noticed that the adafruit DAC has only one analog output and I need to generate three of them.

Hi,

You can find many multi-channel DAC but finding one for the Rpi may be limited. What are your sampling frequencies? Range of signal output levels? Simple search for a 12 bit multi-channel DAC gives me; https://www.element14.com/community/...-eeprom-memory You can look at the data sheet; MCP4728 Data Sheet (.pdf)

Code:

The MCP4728 device is a quad, 12-bit voltage output

Digital-to-Analog  Convertor  (DAC)  with  nonvolatile

memory  (EEPROM).  Its  on-board  precision  output

amplifier  allows  it  to  achieve  rail-to-rail  analog  output

swing.

The  DAC  input  codes,  device  configuration  bits,  and

I2C  address  bits  are  programmable  to  the  nonvolatile

memory  (EEPROM)  by  using  I2C  serial  interface

commands.  The  nonvolatile  memory  feature  enables

the  DAC  device  to  hold  the  DAC  input  codes  during

power-off  time,  allowing  the  DAC  outputs  to  be

available  immediately  after  power-up  with  the  saved

settings.  This  feature  is  very  useful  when  the  DAC

device is used as a supporting device for other devices

in the application’s network.

The  MCP4728  device  has  a  high  precision  internal

voltage reference (VREF= 2.048V). The user can select

the  internal  reference  or  external  reference  (VDD)  for

each channel individually.

Each  channel  can  be  operated  in  Normal  mode  or

Power-Down    mode    individually    by    setting    the

configuration register bits. In Power-Down mode, most

of the internal circuits in the powered down channel are

turned off for power savings, and the output amplifier

can be configured to present a known low, medium, or

high resistance output load.

Since the evaluation board above uses I2c then you could possibly interface with the Rpi

Another device that would work with the Rpi would be the https://www.sparkfun.com/products/12918

Quote:

SparkFun I2C DAC Breakout - MCP4725 $4.95/ea

Description: You’ve always wanted to output analog voltages from a microcontroller, the MCP4725 is the DAC that will let you do it! The MCP4725 is an I2C controlled Digital-to-Analog converter (DAC). A DAC allows you to send analog signal, such as a sine wave, from a digital source, such as the I2C interface on the Arduino microcontroller. Digital to analog converters are great for sound generation, musical instruments, and many other creative projects!
This version of the MCP4725 Breakout fixes a few issues with the board including the IC footprint, the I2C pinout, changes the overall board dimensions to better fit your projects, and a few more minor tweaks. This board breaks out each pin you will need to access and use the MCP4725 including GND and Signal OUT pins for connecting to an oscilloscope or any other device you need to hook up to the board. Also on board are SCL, SDA, VCC, and another GND for your basic I2C pinout. Additionally, if you are looking to have more than one MCP4725 on a bus, the pull-up resistors on this board can be disabled just check the Hookup Guide in the Documents section below for instructions and tips on doing this.
Features:

12-bit resolution
I2C Interface (Standard, Fast, and High-Speed supported)
Small package
2.7V to 5.5V supply
Internal EEPROM to store settings

Documents:

Schematic
Eagle Files
Hookup Guide
Datasheet (MCP4725)
GitHub (Design Files)

By following the hookup guide you can add several devices on the I2c therefore having more DAC for multiple outputs.
Hope this helps.
Have fun And enjoy!
:hattip: