When the program is started, the setup of the memory and internal peripherals is
initiated. This involves the setup of the following peripherals:
ADCC for sampling of the
microphone
DAC for output to the speaker
SPI for interfacing external memory
PORT settings for button interfacing
TMR2 and CLC for button debouncing
TMR0 for correct sampling and playback frequency
DMA for data transfer between peripherals and memory
PWM and Comparator for power amplifier
TMR6 as time base for LED blinking
TMR1 as time base for button press delays
UART for debugging
In addition to the peripherals, external memory is also initialized. If the external
memory can not be identified, then the program defaults to using the internal program
memory as storage.
This is followed by loading the appropriate audio metadata from the EEPROM. The audio
metadata contains the memory location where existing audio is stored and the size of the
audio. If no audio is stored, the audio size is zero bytes.
The setup and main loop functionality is shown in Figure 6-1.
In the PIC18F57Q43 Curiosity Nano, there is only one button
available (SW0 button). In this case, a single button press enters Playback mode, a
double press enters Record mode, and a long-press erases the memory. There is a special
button (SW1 button) available on the custom-made PROTO Click Board™
(see Figure 7-6), along with the power amplifier. A long press of this button enters
into Passthrough mode. This functionality is depicted in Figure 6-2.Figure 6-1. Setup and Main Loop
