gex-thesis/ch.unit.pwmdim.tex

\section{PWM Unit}

The PWM unit uses a timer/counter to generate a PWM signal. There are four outputs with a common frequency and phase, but independent duty cycles. Each channel can be individually enabled or disabled.

This unit is intended for applications like light dimming, heater regulation, or the control of H-bridges.

\subsection{PWM Configuration}

\begin{inicode}
[PWMDIM:pwm@12]
# Default pulse frequency (Hz)
frequency=1000
# Pin mapping - 0=disabled
# Channel1 - 1:PA6, 2:PB4, 3:PC6
ch1_pin=1
# Channel2 - 1:PA7, 2:PB5, 3:PC7
ch2_pin=0
# Channel3 - 1:PB0, 2:PC8
ch3_pin=0
# Channel4 - 1:PB1, 2:PC9
ch4_pin=0
\end{inicode}

\subsection{PWM Commands}

\begin{cmdlist}
    0 & \cname{SET\_FREQUENCY}
    Set the PWM frequency
    & \begin{cmdreq}
        \cfield{u32} frequency in Hz
    \end{cmdreq} \\

    1 & \cname{SET\_DUTY}
    Set the duty cycle of one or more channels
    & \begin{cmdreq}
        \item Repeat 1--4 times:
        \begin{pldlist}
            \cfield{u8} channel number 0--3
            \cfield{u16} duty cycle 0--1000
        \end{pldlist}
    \end{cmdreq} \\

    2 & \cname{STOP}
    Stop the hardware timer. Outputs enter low level.
    & \\

    3 & \cname{START}
    Start the hardware timer.
    & \\
\end{cmdlist}