fhdm-ad9833-pico

A C library for controlling the AD9833 programmable waveform generator using a Raspberry Pi Pico

Quick Start

Connect the Pico to your AD9833 board

• VCC of the AD9833 to 3.3V OUT of the Pico (pin 36)
• DGND and AGND to GND
• FSYNC to GPIO 5
• SCLK to GPIO 6
• SDATA to GPIO 7

Note: The GPIO pin assignments can be changed by calling ad9833.set_pins() before calling ad9833.start()

Configure your CMakeLists.txt file

...

# Add the repository as a subdirectory
# eg.
add_subdirectory(/some-path-on-my-computer/ad9833-pico/lib build)

# Include the library to target_link_libraries
# eg.
target_link_libraries(mytarget 
    fhdm-ad9833-pico
    pico_stdlib 
)
...

Use the library

int main() {

    //  Declare a variable of type 'struct fhdm_ad9833' and initialise it:
    struct fhdm_ad9833 ad9833;
    fhdm_ad9833_pico_new(&ad9833);

    // Optionally set pins, frequency, phase, mclk, mode here otherwise the default
    // values are used. These are:
    // FSYNC PIN - GPIO 5
    // SCLK PIN - GPIO 6
    // SDATA PIN - GPIO 7
    // Frequency: 100Hz
    // Frequency register: 0
    // Phase angle: 0
    // Phase register: 0
    // Output mode: Sine wave

    // Start generating the output signal
    ad9833.start(&ad9833)

    // Change the frequency to 1Hz
    ad9833.set_frequency(&ad9833, 1.0);

    // Change the waveform to a triangle
    ad9833.set_mode(&ad9833, FHDM_AD9833_MODE_TRIANGLE);

    // More of your awesome code goes here
    ...

    return 0;
}

API Usage

You first need to declare a variable of type 'struct fhdm_ad9833' and initialise it:

struct fhdm_ad9833 ad9833;
fhdm_ad9833_pico_new(&ad9833)

All subsequent function calls are made via the ad9833 variable (or whatever you have called it). The first parameter is always a pointer to the ad9833 variable. For example:

ad9833.set_pins(&ad9833, 3, 4, 5);

The AD9833 is initialised and will start generating output when the 'start' function is called. Functions called before calling start will not affect the AD9833 until start is called.

ad9833.start(&ad9833);

API Reference

void set_mclk(struct fhdm_ad9833 *ad9833, uint32_t mclk)

Set the master clock frequency. Default=25Mhz

void set_pins(struct fhdm_ad9833 *ad9833, uint fsync, uint sclk, uint sdata)

Set the GPIO pins to be used for communicating with the AD9833 (use the GPIO number, not the pin number). This method must be called before start(). Default=FSYN:5, SCLK:6, SDATA:7.

void start(struct fhdm_ad9833 *ad9833)

Initialise the AD9833 and start generating waveforms.

void set_frequency(struct fhdm_ad9833 *ad9833, float freq)

Generate output at the given frequency (Hz). Stores the frequency in frequency register 0 and selects that register.

void set_phase(struct fhdm_ad9833 *ad9833, float phase)

Generate output at the given phase angle (radians). Stores the phase in phase angle in register 0 and selects that register.

void set_mode(struct fhdm_ad9833 *ad9833, enum fhdm_ad9833_mode mode)

Set the output type or put the AD9833 in sleep mode. Valid values for mode are FHDM_AD9833_MODE_SLEEP, FHDM_AD9833_MODE_SINE, FHDM_AD9833_MODE_TRIANGLE, FHDM_AD9833_MODE_SQUARE, FHDM_AD9833_MODE_SQUARE_DIV2.

void set_frequency_register_value(struct fhdm_ad9833 *ad9833, int reg_id, float freq)

Store the frequency value in the given frequency register. The output will only change if that register is selected (eg. via select_freqency_register). Valid values for reg_id are 0 and 1.

void select_frequency_register(struct fhdm_ad9833 *ad9833, int reg_id)

Select the frequency register used to generate the output. Valid values for reg_id are 0 and 1.

void set_phase_register_value(struct fhdm_ad9833 *ad9833, int reg_id, float phase)

Store the phase value in the given phase register. The output will only change if that register is selected (eg. via select_phase_register). Valid values for reg_id are 0 and 1.

void select_phase_register(struct fhdm_ad9833 *ad9833, int reg_id)

Select the phase register used to generate the output. Valid values for reg_id are 0 and 1.

Gallery

Square wave

From top to bottom

• AD9833 board controlled by a Raspberry Pi Pico using the ad9833-pico library. Generating a square wave at 100Hz.
• Raspberry Pi Pico running the Scoppy oscilloscope firmware (GPIO 26 is connected to the output of the AD9833)
• The Scoppy Android app on a Nokia 2.1

Sine and Triangle waves