==== dsPIC/PIC32 tone generator ====
<wrap right>
{{:projects:generator:gen.jpg?200}}
</wrap>

This is a  project for the dsPIC33FJ128GP802 or PIC32MX150F128B acting as a tone generator connected to a [[:boards:rpi|Raspberry Pi]].

Four separate tones may be generated simultaneously from five different waves and each tone can be any audible frequency.

A tone may also be triggered and it has a standard four stage envelope (ADSR).

This project is under development and certain aspects may change and features added or removed at any time.

=== Waves ===

There are standard wave types supported for generating tones.

{{:projects:generator:sine.jpg?100}}
{{:projects:generator:triangle.jpg?100}}
{{:projects:generator:sawtooth.jpg?100}}
{{:projects:generator:square.jpg?100}}

A noise generator is also available which operates at the current frequency.

{{:projects:generator:noise.jpg?100}}

=== Schematic ===

This is the bare minimum layout required for this project using the dsPIC with integrated audio DAC. We use a [[:boards:rpi|RPi]] for communication and ICSP.

{{:projects:generator:generator.png?200}}

For PIC32 an external audio DAC is required. Only the CS4334K and PT8211 are supported
at present and are selected at compile time. Connection to either device is as follows.

<columns 50% 50% ->
<code>
CS4334K WITH Vcc = 5V.

PIC32MX150   CS4334K         COMMENT
----------   -------         -------
PIN 15 RPB6  PIN 4 MCLK      128X OVERSAMPLING CLOCK
PIN 16 RPB7  PIN 3 LRCK      SAMPLE RATE LEFT/RIGHT CLOCK
PIN 17 RPB8  PIN 1 SDATA     SERIAL DATA INPUT
PIN 18 RPB9  PIN 2 DEM/SCLK  DE-EMPHASIS FILTER OFF/ON
PIN 25 SCK1                  UNUSED
</code>

</columns>

<columns 50% 50% ->

<code>
PT8211 WITH Vdd = 5V.

PIC32MX150   PT8211          COMMENT
----------   -------         -------
PIN 15 RPB6                  UNUSED
PIN 16 RPB7  PIN 2 WS        SAMPLE RATE LEFT/RIGHT CLOCK
PIN 17 RPB8  PIN 3 SDATA     SERIAL DATA INPUT
PIN 18 RPB9                  UNUSED
PIN 25 SCK1  PIN 1 BCK       SERIAL BIT CLOCK
</code>

</columns>

The CS4334K is a far superior device, but the PT8211 is incredibly cheap (15p each).

=== Firmware ===

For dSPIC First install a working [[:tools:xc16|XC16]] compiler, for PIC32, install [[:tools:xc32|XC32]].

Now build the dsPIC/PIC32 applications.
<code>
hg clone http://hg.kewl.org/pub/generator
cd generator/src
make
</code>

[[:projects:pickle|Pickle]] must be installed and configured and when ready we can write the firmware.

Eg.
<code>
p24 lvp program dspic.hex
</code>

=== Usage ===

Controlling the tone generator is accomplished via the [[:boards:rpi|RPi]] [[:interfaces:amba|UART]] at 115200 baud.

When connected a prompt is displayed which contains the currently selected voice. If no prompt is seen, pressing enter will bring it up.

Commands are entered following a parameter entry. Parameter entry is done via a 32-bit accumulator. As each nibble of a hexadecimal value is entered the current accumulator value is shifted left 4 bits and the new value added. To clear the accumulator, enter eight noughts in succession or a full-stop.

Once the accumulator has been set, and a single character command may be entered. The command operates on the current accumulator value.

=== Commands ===

Here is the command table, most commands operate on the current accumulated value described in usage above.

^Command ^Description |
| .      | The accumulator is reset       |
| +      | The accumulator is incremented |
| -      | The accumulator is decremented |
| ~      | The accumulator low nibble is transferred to the voice function selection byte                 |
| =      | The accumulator is transferred to the voice control word                                       |
| /      | The accumulator low word is transferred to the voice volume word                               |
| %      | The accumulator low word is transferred to the voice square wave duty word                     |
| @      | The accumulater low word is transferred to the voice ADSR envelope generator                   |
| !      | Trigger the voice ADSR envelope                                                                |
| >      | The accumulator low nibble is transferred to the voice selection byte                          |
| \      | The accumulator low word is transferred to the master volume word                              |
| #      | The accumulator low byte is evaluated as a midi note and used to update the voice control word |
| <      | The accumulator is evaluated as a frequency and used to update the voice control word          |
| $      | The accumulator is evaluated as SID HI/LO registers and used to update the voice control word  |

If updating the voice control word directly using '=' (rather than using a midi note, frequency or SID value) the following formula must be used.
<code>
CONTROL WORD = 2^32 / 78000 * FREQUENCY
</code>

Using GNU bc from the shell we can calculate the above for 440 Hz like this.
<code>
printf "%08X=\n" `echo "scale=10; 2^32 / 78000 * 440" | bc`
0171B0B4=
</code>
=== Examples ===

Here are some examples showing the parameter entry followed by a command and the function performed.

^ Entry     ^Function                       |
| 1~        |Select sine waveform           |
| 2~        |Select triangle waveform       |
| 3~        |Select saw-tooth waveform      |
| 4~        |Select square waveform         |
| 5~        |Select noise                   |
| 0~        |Select nothing (OFF)           |
| 7FFF/     |Set max volume                 |
| 8000%     |Set 50% duty cycle             |
| AAAA@     |Set ADSR                       |
| !         |Trigger ADSR                   |


=== Resources ===
[[http://en.wikipedia.org/wiki/Numerically_controlled_oscillator|NCO]]