Aug.13.2021 Mastering YMF-825 part1

Todays topic

When making an ultrasonic musical instrument, I came to think that it would be better if various sounds could be output.

what is YMF-825

Yamaha FM sound source chip YMF825 (SD-1) It is a sound source board equipped with . Equipped with Yamaha’s original FM synthesizer, it is possible to reproduce rich sound by specifying several types of parameters.

Sound is produced by directly controlling the YMF825 register from a microcomputer board such as Arduino or Raspberry Pi through SPI. Since it also has a speaker amplifier, there is no need to prepare an amplifier circuit separately.

* Although it is equipped with a 3.5 mm headphone jack, earphones that use 4-pole CTIA such as for iPhone cannot be used (OMTP ones can be used). ** From Switch science’s sales page **


  • 4 operator FM sound source
  • Up to 16 sounds can be produced at the same time
  • 29 types of FM basic waveforms built-in, 8 types of algorithms
  • SPI Serial interface by
  • Built-in speaker amplifier
  • Built-in 3-band equalizer
  • Built-in 16-bit monaural D / A converter
  • Operating voltage: 5 V
  • 3.3 V can also be used by modifying
** Image quote from Switch science **

A sample sketch is posted on GitHub, so I used it as a reference.

・ Sample sketch a>

Any waveform can be created

The sample sketch also includes a simple manual.

Waveform that YMF825 can produce

Basic, sine wave, triangle wave, sawtooth wave, square wave, half wave rectified wave, etc.


7 types of return can be applied

You can also choose from seven types of return, which are familiar to effectors and synthesizers.

I don’t know the details yet, so I would like to introduce it in the future.

What is SPI Communication

The Serial Peripheral Interface (SPI) is a method of connecting devices used inside a computer, and is used for devices that perform relatively low-speed data transfer.

SPI is a standard proposed by Motorola (currently NXP Semiconductors) as a pin-saving bus.

The signal line consists of 4 lines, and when connecting one device, it can be connected with 3 lines by fixing the SS.

Serial Clock

Master In Slave Out

Master Out Slave In

Slave Select

SPI communication connection (* quoted from Wikipedia)



Simple operation circuit example

Next is the connection diagram.

Connection with YMF-825

Since YMF-825 and Arduino Nano are only communicated in SPI format, connect the power supply line (+ 5V, GND) and SPI terminal (SCK, MISO, MOSI, SS, Reset) to each other.


That’s all for today

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