The digital/analog unit works with the two-channel DAC peripheral of the microcontroller. It can be used in two modes: DC output, and waveform generation.
The waveform mode implements direct digital synthesis (explained in section \ref{sec:theory-dac-dds}) of a sine, rectangle, sawtooth or triangle wave. The generated frequency can be set with a sub-hertz precision up to the lower tens of kHz. The two outputs can use a different waveform shape, be synchronized, and their phase offset, as well as frequency, is dynamically adjustable.
# Superimposed noise type (NONE,WHITE,TRIANGLE) and nbr. of bits (1-12)
ch1_noise=NONE
ch1_noise-level=3
ch2_noise=NONE
ch2_noise-level=3
\end{inicode}
\subsection{DAC Commands}
Channels are specified in all commands as bit map:
\begin{itemize}[nosep]
\item 0x01 - channel 1
\item 0x02 - channel 2
\item 0x03 - both channels affected at once
\end{itemize}
\begin{cmdlist}
0 &\cname{WAVE\_DC}
Set a DC level, disable DDS for the channel
&\begin{cmdreq}
\cfield{u8} channels
\cfield{u16} level (0--4095)
\end{cmdreq}\\
1 &\cname{WAVE\_SINE}
Start a DDS sine waveform
&\begin{cmdreq}
\cfield{u8} channels
\end{cmdreq}\\
2 &\cname{WAVE\_TRIANGLE}
Start a symmetrical triangle waveform
&\begin{cmdreq}
\cfield{u8} channels
\end{cmdreq}\\
3 &\cname{WAVE\_SAWTOOTH\_UP}
Start a rising sawtooth waveform
&\begin{cmdreq}
\cfield{u8} channels
\end{cmdreq}\\
4 &\cname{WAVE\_SAWTOOTH\_DOWN}
Start a dalling sawtooth waveform
&\begin{cmdreq}
\cfield{u8} channels
\end{cmdreq}\\
5 &\cname{WAVE\_RECTANGLE}
Start a rectangle waveform
&\begin{cmdreq}
\cfield{u8} channels
\cfield{u16} on-time (0--8191)
\cfield{u16} high level (0--4095)
\cfield{u16} low level (0--4095)
\end{cmdreq}\\
10 &\cname{SYNC}
Synchronize the two channels. The phase accumulator is reset to zero.
&\\
20 &\cname{SET\_FREQUENCY}
Set the channel frequency
&\begin{cmdreq}
\cfield{u8} channels
\cfield{float32} frequency
\end{cmdreq}\\
21 &\cname{SET\_PHASE}
Set a channel's phase. It's recommended to set the phase only of one channel, leaving the other at 0°.
&\begin{cmdreq}
\cfield{u8} channels
\cfield{u16} phase (0--8191)
\end{cmdreq}\\
22 &\cname{SET\_DITHER}
Control the dithering function of the DAC block. A high noise amplitude can cause an overflow to the other end of the output range due to a bug in the DAC peripheral. Use value 255 to leave the parameter unchanged.
&\begin{cmdreq}
\cfield{u8} channels
\cfield{u8} noise type (0-none, 1-white, 2-triangle)
