AD985X

Arduino library for AD9850 and AD9851 function generators.

Description

Library for the AD9850 and AD9851 function generators. These devices can produce a square and a sine wave

| type | max freq | phase (step size) | Notes | |:--------:|:--------:|:-------------------:|:--------| | AD9850 | 40 MHz | 0..31 x 11.25° | | AD9851 | 70 MHz | 0..31 x 11.25° | has more options.

Note that at the max frequency the devices do not give a nice sine any more. You need to check what is acceptable for your project.

The library has a AD9850 as base class that implements the commonalities. The AD9851 is derived and has its own setFrequency() methods. Furthermore the AD9851 also has function to select the reference clock, a feature the AD9850 does not have. This feature improves the tuning for both low and high frequencies.

Warning The library is not suitable for AD9852 as that is a function generator with way more functionality.

Note: mainly tested on Arduino UNO.

Feedback as always is welcome.

0.7.2 new constructors

Not a breaking change (yet), the library has added new constructors as the spiClock line is not needed any more. See #37. Also a new constructor is added to work without a select pin (always selected).

0.5.0 Breaking change

Version 0.5.0 introduced a breaking change to improve handling the SPI dependency. The user has to call SPI.begin() or equivalent before calling AD.begin(). Optionally the user can provide parameters to the SPI.begin(...)

0.4.0 Breaking change

The version 0.4.0 has breaking changes in the interface. The essence is removal of ESP32 specific code from the library. Furthermore it moved parameters from begin() to the constructor. Finally made a specific constructor for HW SPI and SW SPI. This makes it possible to support the ESP32-S3 and other processors in the future. Also it makes the library a bit simpler to maintain.

Connection

Schema break-out

          TOP VIEW
        +-----------+
        |   X-TAL   |
        |         L |
    VCC | o       o | VCC
    CLK | o       o | D0
   PUFD | o       o | D1
   DATA | o       o | D2
  RESET | o       o | D3
    GND | o CCC   o | D4
  QOUT1 | o CCC   o | D5
  QOUT2 | o       o | D6
  ZOUT1 | o       o | D7 ----- SELECT SERIAL LOW
  ZOUT2 | o  PP   o | GND
        |    PP     |
        +-----------+

  XTAL = crystal
  L    = LED
  C    = chip
  P    = potentiometer => for duty cycle square wave

Related

• https://github.com/RobTillaart/AD9833
• https://github.com/RobTillaart/AD985X
• https://github.com/RobTillaart/functionGenerator software waveform generator
• https://pages.mtu.edu/~suits/notefreqs.html frequency table for notes.

Multi device

See Multi_AD985X_devices.pdf

Discussion leading to the document see - https://github.com/RobTillaart/AD985X/issues/13

The AD985X board can be connected with a SPI bus like interface. However there is no Chip Select pin (CS) so one must take other measures to control multiple AD985X devices.

Trivial solution

The trivial implementation is to give each device a set of unique pins. If you have pins to spare this is the perfect solution.

Shared line solution

A more common SPI solution is to share the data and clock lines. However that would typical set all AD985X devices simultaneously. So extra hardware is needed to prevent this.

A possible solution is to put all needed lines behind an AND port that allows only communication when the SELECT is HIGH.

     Arduino        AND           AD985X
--------------------------------------------------
 
                +--------+
     SELECT ----| A      |
                |      Y |------- DATA
     DATA  -----| B      |
                +--------+
  
                +--------+
     SELECT ----| A      |
                |      Y |------- CLOCK
     CLOCK  ----| B      |
                +--------+
 
                +--------+
     SELECT ----| A      |
                |      Y |------- FQ_UD
     FQ_UD  ----| B      |
                +--------+
 
                +--------+
     SELECT ----| A      |
                |      Y |------- RESET
     RESET  ----| B      |
                +--------+

The DATA line of the device is connected to the output of an AND port.
The inputs if the AND port are (a) the SPI bus DATA line and (b) the SELECT pin.
Strictly for the DATA this is not needed as data will only clock in if there is a CLOCK.

The CLOCK pin of the device is connected to the output of an AND port.
The inputs if the AND port are (a) the SPI bus CLOCK line and (b) the SELECT pin.

The FQ_UD pin of the device is connected to the output of an AND port.
The inputs if the AND port are (a) the MCU FQ_UD line and (b) the SELECT pin. See FQ_UD note below.

The RESET pin of the device is connected to the output of an AND port.
The inputs if the AND port are (a) the MCU RESET line and (b) the SELECT pin.

A typical IC to use is the 74HC08 which has 4 AND ports in it.

In short this setup makes the lines 'switchable' pass through, with the SELECT line. It allows to have multiple AD985X devices, and even to share the SPI bus DATA and CLOCK lines with other SPI devices.

FQ_UD note

It might be possible to connect a single FQ_UD line to multiple AD985X devices directly. The FQ_UD pulse would update the frequency and as this register is not changed, the FQ_UD pulse might just have no changing effect. To be investigated to confirm this.

If confirmed this would change the above Shared line solution a bit.

If the FQ_UD line can be shared directly it offers a way to start / change multiple devices at the same time.

Interface

#include "AD985X.h"

Constructors

There are constructors with and without SELECT pin, e.g. if device is continuously selected.

• select = chip select. The library uses HIGH as active and LOW as not selected.
• resetPin = reset
• FQUDPin = Frequency UpDate Pin

HW SPI

• AD9850(uint8_t select, uint8_t resetPin, uint8_t FQUDPin, SPIClassRP2040 * mySPI) hardware SPI constructor RP2040
• AD9850(uint8_t select, uint8_t resetPin, uint8_t FQUDPin, SPIClass * mySPI) hardware SPI constructor.
• AD9850(uint8_t resetPin, uint8_t FQUDPin, SPIClassRP2040 * mySPI) hardware SPI constructor RP2040
• AD9850(uint8_t resetPin, uint8_t FQUDPin, SPIClass * mySPI) hardware SPI constructor.

SW SPI

• AD9850(uint8_t select, uint8_t resetPin, uint8_t FQUDPin, uint8_t spiData, uint8_t spiClock)
• AD9850(uint8_t resetPin, uint8_t FQUDPin, uint8_t spiData, uint8_t spiClock)
• AD9851(...) constructors with same interface as AD9850

Deprecated

Deprecated as spiClock no longer needed.

• AD9850(uint8_t select, uint8_t resetPin, uint8_t FQUDPin, SPIClassRP2040 * mySPI, uint8_t spiClock) hardware SPI constructor RP2040.
• AD9850(uint8_t select, uint8_t resetPin, uint8_t FQUDPin, SPIClass * mySPI, uint8_t spiClock) hardware SPI constructor.

Common interface

• void begin() initializes library internals.
• void reset() resets the function generator.
• void powerDown() idem.
• void powerUp() idem.

Frequency and phase

• bool setFrequency(uint32_t freq) SetFrequency sets the frequency and is limited by the MaxFrequency of the class used. Returns false if limited. For the AD9850 => 40 MHz, for the AD9851 => 70 MHz.
  • Note that the quality of the signal gets less at higher frequencies.
  • Note setFrequency is affected by the autoUpdateFlag.
• bool setFrequencyF(float freq) SetFrequencyF sets the frequency with a float with a maximum of two decimals.
  • Note that a float only has a mantissa of 6-7 digits so for frequencies above above ~1.000.000 = 1MHz all decimals are lost.
  • Note setFrequencyF is affected by the autoUpdateFlag. The frequency is limited by the MaxFrequency of the class used. Returns false if limited.
• uint32_t getMaxFrequency() returns the maximum frequency that can be set.
  • For the AD9850 this is 20 MHz.
  • For the AD9851 this is 70 MHz.
• float getFrequency() returns the frequency set. As it returns a float it might loose some accuracy at higher frequencies.
• bool setPhase(uint8_t phase = 0) set the phase in units of 11.25° 0..31 allowed. Default it sets the phase to 0. Returns false if phase > 31, no change to phase in that case.
• uint8_t getPhase() returns the phase set, 0 by default.
  • multiply by 11.25° to get the actual phase angle in degrees.
  • multiply by (PI * 0.0625) to get actual phase angle in radians.

Calibration

Warning: use with care.

• void setCalibrationOffset(int32_t offset = 0) sets an offset to calibrate the frequency.
• uint32_t getCalibrationOffset() reads back t