AUDIO input and Raspberry Pi Pico

[baritonomarchetto]

Hello,

I am trying to figure out how to read an audio input and output it as-it-is with Mozzi.
Using a Pi Pico (Earl Phil Hower core) and PT8211 DAC.

All libraries and core updated.

Here is the full sketch:

#include <MozziConfigValues.h>
#define MOZZI_AUDIO_MODE MOZZI_OUTPUT_I2S_DAC //external I2C DAC
#define MOZZI_AUDIO_CHANNELS MOZZI_STEREO //one voice per-channel
//#define MOZZI_AUDIO_RATE 32678 //default
//#define MOZZI_CONTROL_RATE 64  //default
#define MOZZI_ANALOG_READ_RESOLUTION 12   //Pi Pico default
#define MOZZI_AUDIO_BITS 16 //default
#define MOZZI_I2S_PIN_BCK 2 //default 20. To DAC pin 1 (BCK)
//#define MOZZI_I2S_PIN_WS (MOZZI_I2S_PIN_BCK+1) // CANNOT BE CHANGED, HAS TO BE NEXT TO pBCLK, i.e. default is 21. To DAC pin 2 (WS)
#define MOZZI_I2S_PIN_DATA 4 //default 22. To DAC pin 3 (DIN)
#define MOZZI_I2S_FORMAT MOZZI_I2S_FORMAT_LSBJ //PT8211 mode as per PT8211 datasheet

#define MOZZI_AUDIO_INPUT MOZZI_AUDIO_INPUT_STANDARD
#define MOZZI_AUDIO_INPUT_PIN A0 //A0

#include <Mozzi.h>

int16_t rawData;
int16_t currentData;

void setup(){
  startMozzi();
}

void updateControl(){
  // put changing controls in here.
}

AudioOutput updateAudio(){
  rawData = getAudioInput(); //0-4095 (12 bit)
  currentData = (rawData - 2048) << 4; // 12 bit unsigned → 16 bit signed conversion
  return StereoOutput::fromNBit(16, currentData, currentData); //N is the number of bit of currentData
}

void loop(){
  audioHook(); // required here
}

It does not compile. The error is:

FQBN: rp2040:rp2040:rpipico
Using board 'rpipico' from platform in folder: C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0
Using core 'rp2040' from platform in folder: C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0

Detecting libraries used...
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\sketch\ProgExpPedalMozziDebug.ino.cpp -o nul
Alternatives for MozziConfigValues.h: [Mozzi@2.0.2]
ResolveLibrary(MozziConfigValues.h)
  -> candidates: [Mozzi@2.0.2]
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\sketch\ProgExpPedalMozziDebug.ino.cpp -o nul
Alternatives for FixMath.h: [FixMath@1.0.9]
ResolveLibrary(FixMath.h)
  -> candidates: [FixMath@1.0.9]
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi -Ic:\Users\HOME\Documents\Arduino\libraries\FixMath\src C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\sketch\ProgExpPedalMozziDebug.ino.cpp -o nul
Alternatives for I2S.h: [I2S@2.0]
ResolveLibrary(I2S.h)
  -> candidates: [I2S@2.0]
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi -Ic:\Users\HOME\Documents\Arduino\libraries\FixMath\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S\src C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\sketch\ProgExpPedalMozziDebug.ino.cpp -o nul
Alternatives for AudioBufferManager.h: [AudioBufferManager@1.0.0]
ResolveLibrary(AudioBufferManager.h)
  -> candidates: [AudioBufferManager@1.0.0]
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi -Ic:\Users\HOME\Documents\Arduino\libraries\FixMath\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\AudioBufferManager\src C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\sketch\ProgExpPedalMozziDebug.ino.cpp -o nul
Using cached library dependencies for file: c:\Users\HOME\Documents\Arduino\libraries\Mozzi\mozzi_fixmath.cpp
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi -Ic:\Users\HOME\Documents\Arduino\libraries\FixMath\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\AudioBufferManager\src -IC:\Users\HOME\Documents\Arduino\libraries\Mozzi\utility c:\Users\HOME\Documents\Arduino\libraries\Mozzi\utility\FrequencyTimer2.cpp -o nul
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi -Ic:\Users\HOME\Documents\Arduino\libraries\FixMath\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\AudioBufferManager\src -IC:\Users\HOME\Documents\Arduino\libraries\Mozzi\utility c:\Users\HOME\Documents\Arduino\libraries\Mozzi\utility\TimerOne.cpp -o nul
Using cached library dependencies for file: C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S\src\I2S.cpp
Using cached library dependencies for file: C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\AudioBufferManager\src\AudioBufferManager.cpp
Generating function prototypes...
C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\tools\pqt-gcc\4.1.0-1aec55e/bin/arm-none-eabi-g++ -I C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 -DUSB_MANUFACTURER="Raspberry Pi" -DUSB_PRODUCT="Pico" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 -DARDUINO_VARIANT="rpipico" -DPICO_FLASH_SIZE_BYTES=2097152 @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/platform_def.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_def.txt -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -iprefixC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/ @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/rp2040/platform_inc.txt @C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/lib/core_inc.txt -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0/include -fno-rtti -std=gnu++17 -g -pipe -w -x c++ -E -CC -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO -DBOARD_NAME="RASPBERRY_PI_PICO" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\cores\rp2040 -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\variants\rpipico -Ic:\Users\HOME\Documents\Arduino\libraries\Mozzi -Ic:\Users\HOME\Documents\Arduino\libraries\FixMath\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S\src -IC:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\AudioBufferManager\src C:\Users\HOME\AppData\Local\arduino\sketches\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\sketch\ProgExpPedalMozziDebug.ino.cpp -o C:\Users\HOME\AppData\Local\Temp\2878737122\sketch_merged.cpp
C:\Users\HOME\AppData\Local\Arduino15\packages\builtin\tools\ctags\5.8-arduino11/ctags -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives C:\Users\HOME\AppData\Local\Temp\2878737122\sketch_merged.cpp

Compiling sketch...
"C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\tools\\pqt-python3\\1.0.1-base-3a57aed-1/python3" -I "C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/tools/signing.py" --mode header --publickey "C:\\Users\\HOME\\Desktop\\ProgExpPedalMozziDebug/public.key" --out "C:\\Users\\HOME\\AppData\\Local\\arduino\\sketches\\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core/Updater_Signing.h"
"C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\tools\\pqt-gcc\\4.1.0-1aec55e/bin/arm-none-eabi-g++" -I "C:\\Users\\HOME\\AppData\\Local\\arduino\\sketches\\6BCD2A9DC1D50ABBE938B4DA9C57C7B7/core" -c -Werror=return-type -Wno-psabi -DUSBD_PID=0x000a -DUSBD_VID=0x2e8a -DUSBD_MAX_POWER_MA=250 "-DUSB_MANUFACTURER=\"Raspberry Pi\"" "-DUSB_PRODUCT=\"Pico\"" -DLWIP_IPV6=0 -DLWIP_IPV4=1 -DLWIP_IGMP=1 -DLWIP_CHECKSUM_CTRL_PER_NETIF=1 -DFILE_COPY_CONSTRUCTOR_SELECT=FILE_COPY_CONSTRUCTOR_PUBLIC -DUSE_UTF8_LONG_NAMES=1 -DDISABLE_FS_H_WARNING=1 "-DARDUINO_VARIANT=\"rpipico\"" -DPICO_FLASH_SIZE_BYTES=2097152 "@C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/lib/platform_def.txt" "@C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/lib/rp2040/platform_def.txt" -march=armv6-m -mcpu=cortex-m0plus -mthumb -ffunction-sections -fdata-sections -fno-exceptions -MMD "-iprefixC:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/" "@C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/lib/rp2040/platform_inc.txt" "@C:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/lib/core_inc.txt" "-IC:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0/include" -fno-rtti -std=gnu++17 -g -pipe -DF_CPU=200000000L -DARDUINO=10607 -DARDUINO_RASPBERRY_PI_PICO "-DBOARD_NAME=\"RASPBERRY_PI_PICO\"" -DARDUINO_ARCH_RP2040 -Os -DWIFICC=CYW43_COUNTRY_WORLDWIDE "-IC:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0\\cores\\rp2040" "-IC:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0\\variants\\rpipico" "-Ic:\\Users\\HOME\\Documents\\Arduino\\libraries\\Mozzi" "-Ic:\\Users\\HOME\\Documents\\Arduino\\libraries\\FixMath\\src" "-IC:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0\\libraries\\I2S\\src" "-IC:\\Users\\HOME\\AppData\\Local\\Arduino15\\packages\\rp2040\\hardware\\rp2040\\5.3.0\\libraries\\AudioBufferManager\\src" "C:\\Users\\HOME\\AppData\\Local\\arduino\\sketches\\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\\sketch\\ProgExpPedalMozziDebug.ino.cpp" -o "C:\\Users\\HOME\\AppData\\Local\\arduino\\sketches\\6BCD2A9DC1D50ABBE938B4DA9C57C7B7\\sketch\\ProgExpPedalMozziDebug.ino.cpp.o"
In file included from c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/MozziGuts.hpp:59,
                 from c:\Users\HOME\Documents\Arduino\libraries\Mozzi/MozziGuts.h:205,
                 from c:\Users\HOME\Documents\Arduino\libraries\Mozzi/Mozzi.h:33,
                 from C:\Users\HOME\Desktop\ProgExpPedalMozziDebug\ProgExpPedalMozziDebug.ino:16:
c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/MozziGuts_impl_RP2040.hpp:298:2: warning: #warning Automatic random seeding is not implemented on this platform [-Wcpp]
  298 | #warning Automatic random seeding is not implemented on this platform
      |  ^~~~~~~
In file included from c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/config_checks_generic.h:38,
                 from c:\Users\HOME\Documents\Arduino\libraries\Mozzi/MozziGuts.h:31:
c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/mozzi_macros.h:25:117: error: static assertion failed: Compile time option MOZZI_AUDIO_INPUT does not support value 202 on this platform.
   24 |                    (X == A0 || X == A1 || X == A2 || X == A3 || X == A4 || X == A5 || X == A6 || X == A7 || X == A8 || X == A9 || \
      |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   25 |                     X == B0 || X == B1 || X == B2 || X == B3 || X == B4 || X == B5 || X == B6 || X == B7 || X == B8 || X == B9), "Compile time option " M " does not support value " #X " on this platform.");
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/mozzi_macros.h:28:32: note: in definition of macro 'MOZZI__MACRO_EVAL'
   28 | #define MOZZI__MACRO_EVAL(...) __VA_ARGS__
      |                                ^~~~~~~~~~~
c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/mozzi_macros.h:35:57: note: in expansion of macro 'MOZZI__CHECK_SUPPORTED'
   35 | #define MOZZI_CHECK_SUPPORTED(X, ...) MOZZI__MACRO_EVAL(MOZZI__CHECK_SUPPORTED(X, #X, __VA_ARGS__, \
      |                                                         ^~~~~~~~~~~~~~~~~~~~~~
c:\Users\HOME\Documents\Arduino\libraries\Mozzi/internal/config_checks_rp2040.h:128:1: note: in expansion of macro 'MOZZI_CHECK_SUPPORTED'
  128 | MOZZI_CHECK_SUPPORTED(MOZZI_AUDIO_INPUT, MOZZI_AUDIO_INPUT_NONE, MOZZI_ANALOG_READ_STANDARD)
      | ^~~~~~~~~~~~~~~~~~~~~
Using library Mozzi at version 2.0.2 in folder: C:\Users\HOME\Documents\Arduino\libraries\Mozzi 
Using library FixMath at version 1.0.9 in folder: C:\Users\HOME\Documents\Arduino\libraries\FixMath 
Using library I2S at version 2.0 in folder: C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\I2S 
Using library AudioBufferManager at version 1.0.0 in folder: C:\Users\HOME\AppData\Local\Arduino15\packages\rp2040\hardware\rp2040\5.3.0\libraries\AudioBufferManager 
exit status 1

Compilation error: exit status 1

Thanks in advance for the help.

[tomcombriat]

Hi,
Thanks for pointing that out. At first glance seems to be that Mozzi does not consider the audio input mode as valid for the Rp2040, but I thought it did.

Will try to have a look once I manage to lay my hands on a computer!

[baritonomarchetto]

Sorry to bother Tom, did you eventually had the time to take a look? :)

Thanks!

Hi, Thanks for pointing that out. At first glance seems to be that Mozzi does not consider the audio input mode as valid for the Rp2040, but I thought it did.

Will try to have a look once I manage to lay my hands on a computer!

[tomcombriat]

No problem, I actually just did ;). Could you try #316 and report back if it works successfully?

[baritonomarchetto]

Made the modification you linked. Now it does compile!

BUT

Still doesn't work for me.

I am sending inputs to Pico pin 26 (A0) by tapping on 3.3V line with a jumper.

The following version of the code works (mozzi analog read), which makes me exclude an hadware/wiring issue on my setup:

#include <MozziConfigValues.h>
#define MOZZI_AUDIO_MODE MOZZI_OUTPUT_I2S_DAC //external I2C DAC
#define MOZZI_AUDIO_CHANNELS MOZZI_STEREO //one voice per-channel
//#define MOZZI_AUDIO_RATE 32678 //default
//#define MOZZI_CONTROL_RATE 64  //default
#define MOZZI_ANALOG_READ_RESOLUTION 12   //Pi Pico default
#define MOZZI_AUDIO_BITS 16 //default
#define MOZZI_I2S_PIN_BCK 2 //default 20. To DAC pin 1 (BCK)
//#define MOZZI_I2S_PIN_WS (MOZZI_I2S_PIN_BCK+1) // CANNOT BE CHANGED, HAS TO BE NEXT TO pBCLK, i.e. default is 21. To DAC pin 2 (WS)
#define MOZZI_I2S_PIN_DATA 4 //default 22. To DAC pin 3 (DIN)
#define MOZZI_I2S_FORMAT MOZZI_I2S_FORMAT_LSBJ //PT8211 mode as per PT8211 datasheet

//#define MOZZI_AUDIO_INPUT MOZZI_AUDIO_INPUT_STANDARD
//#define MOZZI_AUDIO_INPUT_PIN A0 //A0

#include <Mozzi.h>

int16_t rawData;
int16_t currentData;

void setup(){
  startMozzi();
}

void updateControl(){
  // put changing controls in here.
}

AudioOutput updateAudio(){
  //rawData = getAudioInput(); //0-4095 (12 bit)
  rawData = mozziAnalogRead(26); //A0
  currentData = (rawData - 2048) << 4; // 12 bit unsigned → 16 bit signed conversion
  return StereoOutput::fromNBit(16, currentData, currentData); //N is the number of bit of currentData
}

void loop(){
  audioHook(); // required here
}

This one uses instead MOZZI_AUDIO_INPUT_STANDARD. Compiles but doesn't work:

#include <MozziConfigValues.h>
#define MOZZI_AUDIO_MODE MOZZI_OUTPUT_I2S_DAC //external I2C DAC
#define MOZZI_AUDIO_CHANNELS MOZZI_STEREO //one voice per-channel
//#define MOZZI_AUDIO_RATE 32678 //default
//#define MOZZI_CONTROL_RATE 64  //default
#define MOZZI_ANALOG_READ_RESOLUTION 12   //Pi Pico default
#define MOZZI_AUDIO_BITS 16 //default
#define MOZZI_I2S_PIN_BCK 2 //default 20. To DAC pin 1 (BCK)
//#define MOZZI_I2S_PIN_WS (MOZZI_I2S_PIN_BCK+1) // CANNOT BE CHANGED, HAS TO BE NEXT TO pBCLK, i.e. default is 21. To DAC pin 2 (WS)
#define MOZZI_I2S_PIN_DATA 4 //default 22. To DAC pin 3 (DIN)
#define MOZZI_I2S_FORMAT MOZZI_I2S_FORMAT_LSBJ //PT8211 mode as per PT8211 datasheet

#define MOZZI_AUDIO_INPUT MOZZI_AUDIO_INPUT_STANDARD
#define MOZZI_AUDIO_INPUT_PIN A0 //A0

#include <Mozzi.h>

int16_t rawData;
int16_t currentData;

void setup(){
  startMozzi();
}

void updateControl(){
  // put changing controls in here.
}

AudioOutput updateAudio(){
  rawData = getAudioInput(); //0-4095 (12 bit)
  //rawData = mozziAnalogRead(26); //A0
  currentData = (rawData - 2048) << 4; // 12 bit unsigned → 16 bit signed conversion
  return StereoOutput::fromNBit(16, currentData, currentData); //N is the number of bit of currentData
}

void loop(){
  audioHook(); // required here
}

Any hint?

(many thanks for the help so far!!)

[tomcombriat]

Ah… A typo only would have been too easy…

I'll need to test with some hardware (and get into the AudioInput code), will keep you updated, I should have a bit of time today but no guarantee ;).

[baritonomarchetto]

much appreciated 👍

[tomcombriat]

Alright, seems a bit more complicated. Actually, mozziAnalogRead does not work when Audio Input is activated which points toward a deeper problem/limitation with the asynchroneous ADCs reads.

I will dig deeper but I would like first to confirm that only RP2040 is affected or not, but do not have the hardware with me atm (I only have an RP and a PT8211, good coincidence though). I anyone reading this (@sensorium , @tfry-git ?) has the opportunity to try, otherwise I might have access to some in a few days.

As a stopgap, you can always put the control rate quite high and use mozziAnalogRead()… Not very clean but…

[baritonomarchetto]

I made a try just to figure out that UNO and Leonardo don't support MOZZI_OUTPUT_I2S_DAC.

If there's something I can test with one of these, let me know!

[tomcombriat]

Hum, I hope the external output is not linked into this too…
If you have the time you can try:

• on the RP2040 without using the DAC (basic PWM output)
• on any AVR, using PWM, see if the Audio Input breaks mozziAnalogRead().

Here is an example sketch that I use for that:

#include "MozziConfigValues.h"  // for named option values
//#define MOZZI_AUDIO_MODE MOZZI_OUTPUT_I2S_DAC
//#define MOZZI_I2S_FORMAT MOZZI_I2S_FORMAT_LSBJ
#define MOZZI_CONTROL_RATE 256  // Hz, powers of 2 are most reliable; 64 Hz is actually the default, but shown here, for clarity

#define MOZZI_AUDIO_INPUT MOZZI_AUDIO_INPUT_STANDARD
#define MOZZI_AUDIO_INPUT_PIN A0  //A0
#include <Mozzi.h>
#include <Oscil.h>                // oscillator template
#include <tables/sin2048_int8.h>  // sine table for oscillator

// use: Oscil <table_size, update_rate> oscilName (wavetable), look in .h file of table #included above
Oscil<SIN2048_NUM_CELLS, MOZZI_AUDIO_RATE> aSin(SIN2048_DATA);

void setup() {
  Serial.begin(115200);
  startMozzi();       // :)
  aSin.setFreq(220);  // set the frequency
}
uint8_t vol;



void updateControl() {
  vol = mozziAnalogRead<8>(A1);  // or any other pin, just to check that mozziAnalogRead works
                                 // aSin.setFreq(vol);
                                 //Serial.println(runner);
}


AudioOutput updateAudio() {
  int16_t tt = getAudioInput();
  return MonoOutput::from16Bit(aSin.next() * vol + tt);  // return an int signal centred around 0
}


void loop() {
  audioHook();  // required here
}

using this, linking a pot to A1 (or bridging it to GND or Vpp) should change the volume of the sin wave if #define MOZZI_AUDIO_INPUT MOZZI_AUDIO_INPUT_STANDARD did not break anything.

[tfry-git]

Alright, seems a bit more complicated. Actually, mozziAnalogRead does not work when Audio Input is activated which points toward a deeper problem/limitation with the asynchroneous ADCs reads.

I will dig deeper but I would like first to confirm that only RP2040 is affected or not, but do not have the hardware with me atm (I only have an RP and a PT8211, good coincidence though). I anyone reading this (@sensorium , @tfry-git ?) has the opportunity to try, otherwise I might have access to some in a few days.

As a stopgap, you can always put the control rate quite high and use mozziAnalogRead()… Not very clean but…

I'm quite certain that mozziAnalogRead() and getAudioInput() are supposed to work in parallel, where supported. I'm not quite sure what exactly I had meant to express in that config check for RK2040. Yes, it's an obvious typo, but what for? Would need to take a deeper look, probably not all too soon.

[tomcombriat]

@tfry-git If i remember correctly, this was done in order to accommodate potential other ways to get an audio input (i2S for instance, which had been in my mind for some time). But why does the adc reads break when the adc loop is ran at audio rate, mystery for now (but I did not look very far..). Could maybe be because the adc did not have time to finish the previous conversion before we ask for a new one?

[sensorium]

I tested a version of Tom's sketch today with an AVR and it's working on that platform.

[baritonomarchetto]

Tested on Arduino Leonardo and Tom's sketch works (I see the square wave duty cycle changing accordingly to pot position wired to A1)

[tomcombriat]

Further tests here, this is not linked to the I2S output, on the RP2040 it also happens in PWM (default mode).

I am actually wondering if this is not a bit broader than initially though and if that is not linked to BYPASS_MOZZI_OUTPUT_BUFFER: I think BYPASS_MOZZI_OUTPUT_BUFFER used together with AUDIO_INPUT does not work, and breaks all ADC readings (and the audio input as a consequence).

I actually managed to partially fix it in this commit: 3961680

#if BYPASS_MOZZI_OUTPUT_BUFFER == true
uint64_t samples_written_to_buffer = 0;
inline void bufferAudioOutput(const AudioOutput f) {
  audioOutput(f);
  ++samples_written_to_buffer;
/////// THIS COMMIT START
  #if MOZZI_IS(MOZZI__LEGACY_AUDIO_INPUT_IMPL, 1) // in that case, we rely on asynchroneous ADC reads implemented for mozziAnalogRead to get the audio in samples
  MOZZI_ASSERT_NOTEQUAL(MOZZI_ANALOG_READ, MOZZI_ANALOG_READ_NONE);
  adc_count = 0;
  startSecondADCReadOnCurrentChannel();
///////// THIS COMMIT ENDS
 #endif


}
#else
CircularBuffer<AudioOutput> output_buffer;  // fixed size 256
#  define canBufferAudioOutput() (!output_buffer.isFull())
#  define bufferAudioOutput(f) output_buffer.write(f)
static void CACHED_FUNCTION_ATTR defaultAudioOutput() {
#if MOZZI_IS(MOZZI__LEGACY_AUDIO_INPUT_IMPL, 1) // in that case, we rely on asynchroneous ADC reads implemented for mozziAnalogRead to get the audio in samples
  MOZZI_ASSERT_NOTEQUAL(MOZZI_ANALOG_READ, MOZZI_ANALOG_READ_NONE);
  adc_count = 0;
  startSecondADCReadOnCurrentChannel();  // the current channel is the AUDIO_INPUT pin
#  endif
  audioOutput(output_buffer.read());
}
#endif  // #if (AUDIO_INPUT_MODE == AUDIO_INPUT_LEGACY)
////// END Output buffering ///////

This works, sometimes, depending on the sketch. When enough time is spent in updateAudio() then it works fine. Otherwise, the other ADC channels, probed with mozziAnalogRead leak inside the audio input (the audio input then mostly take the value of another analog channel, and sometimes the value of the input*), indicating a problem in the async ADC scheduling (advanceADCStep()).

WIP, as I have to admit that I am still in the process of understanding completely how the ADC control loop works…

Edit:

* The audio input takes the value of the last read analog pin in updateControl() most of the time, so I am starting to wonder if the ADC would not be too slow, and the loop does not have the time to exit case 1 before being called back to case 0 by bufferAudioOutput:

inline void advanceADCStep() {
  switch (adc_count) {
  case 0:
    // 6us
    // the input pin was the last thing we read 
    input_buffer.write(getADCReading());
    adcReadSelectedChannels();     // TODO: doesn't this stop the cycle, in case no pins to read?
    break;

  case 1:
    // <2us, <1us w/o receive
    // receiveFirstControlADC();
    startSecondADCReadOnCurrentChannel();
    break;

  case 2:
    // 3us
    analog_readings[channelNumToIndex(current_channel)] = getADCReading();
    adcStartConversion(adcPinToChannelNum(MOZZI_AUDIO_INPUT_PIN));  // -> result is ignored, but first thing in the next cycle, a second reading is taken.
    break;

  }
  adc_count++;
}