Audio Range Frequency Generator

This is a sine wave generator that works in the range from 20 Hz to 20 KHz. The signal is generated digitally by an STM32F411 microcontroller and converted to analog by a PCM5102A DAC.

• STM32F411 board.
• PCM5102A DAC module. The module must be able to be configured for "left justified" format.
• Rotary encoder with button.
• 8 digits numerical display using MAX7219 chip.

You will also need

• a computer running Windows or Linux.
• an STLink programmer.
• connection wires (female to female).
• a soldering iron and solder.
• USB cable

Use a soldering iron to remove the connection 4-L and make the connection 4-H.

This way the DAC is configured for "left justified" format instead of "I2S".

Download and install STM32CubeProg from st.com

Visit page st.com

Search in "products" for "STM32CubeProg" and select the "STM32CubeProg line.

Go to the "Get Software" section and select the version that fits to your operating system.

(For more informations on installation, search in "resources" for "UM2563".)

(you have to register with an e-mail in order to download the software).

Download file "FreqGen.hex".

Use the "ST-Link V2" to flash the microcontroller.

Connect MCU board with ST-Link through GND/SWSCK/SWDIO/3V3 pins

Connect the ST-Link in a USB port

Run the STM32CubeProg

Click the "Connect" button

Click "Open File" and load the hex file.

Click "Download" and after the program is loaded, click "Disconnect"

The MCU is ready!

Connections between MCU and DAC

DAC------- MCU

---------------------

VIN ------- 3.3V

GND ------ GND

LRCK ----- B12

DIN -------- B15

BCK ------- B10

Connections between Rotary Encoder and MCU

Encoder ------- MCU

---------------------------

CLK -------- B5

DT ---------- B4

SW --------- B6

+ ------------ 3.3V

GND ------- GND

(Note: CLK and DT may be marked as A and B)

Connections between MCU and Display

Display ----- MCU

-----------------------

VCC ----- 5V

GND ---- GND

DIN ------ A7

CS ------- B0

CLK ----- A5

Connect an earphone at DAC's output.

Power up the MCU using a USB cable.

The initial frequency is 77.215 Hz. Use the rotary encoder to increase or decrease it. Push the encoder's button to change the state from "coarse" to "fine". Now you can use the encoder to fine-tune the frequency. Push it again to return to "coarse".

(Note: the accuracy of the frequency depends on the accuracy of the crystal used by the MCU board. An additional 0.02% frequency error is introduced from the conversion of the crystal frequency to the DAC's clock)

Enjoy!