AudioLoRaConfig Struct Reference

Configuration for AudioLoRa. More...

#include <AudioLoRa.h>

Inheritance diagram for AudioLoRaConfig:

Public Member Functions
virtual void	clear ()
void	copyFrom (AudioInfo info)
	Same as set.
bool	equals (AudioInfo alt)
	Returns true if alt values are the same like the current values.
bool	equalsExSampleRate (AudioInfo alt)
	Checks if only the sample rate is different.
virtual void	logInfo (const char *source="")
	operator bool ()
	Returns true if all components are defined (no component is 0)
bool	operator!= (AudioInfo alt)
	Returns true if alt values are the different from the current values.
bool	operator== (AudioInfo alt)
	Returns true if alt values are the same like the current values.
void	set (AudioInfo info)
	Copies the values from info.
void	setAudioInfo (AudioInfo info)
	Same as set.

Public Attributes
uint8_t	bits_per_sample = DEFAULT_BITS_PER_SAMPLE
	Number of bits per sample (int16_t = 16 bits)
uint16_t	channels = DEFAULT_CHANNELS
	Number of channels: 2=stereo, 1=mono.
int	frequency = 868E6
int	max_size = 200
int	pin_dio0 = 14
int	pin_rst = 12
int	pin_ss = 8
bool	process_audio_info = true
sample_rate_t	sample_rate = DEFAULT_SAMPLE_RATE
	Sample Rate: e.g 44100.
int	signal_bandwidth
int32_t	spi_speed = 8E6
int	spreading_factor = 6
int	sync_word = 0xF3
int	tx_power = 20

Detailed Description

Configuration for AudioLoRa.

LoRa is a long-range, low-power radio technology designed for occasional telemetry (a few bytes every so often), not for continuous audio. LoRa's PHY settings trade range/robustness for throughput: spreading_factor ranges from 6 (fastest, shortest range) to 12 (slowest, longest range), and signal_bandwidth from 7.8 kHz (slowest, longest range) to 500 kHz (fastest, shortest range). The defaults below (spreading_factor = 6, signal_bandwidth = 500 kHz) pick LoRa's fastest, shortest-range end of that scale, since audio needs throughput far more than a typical LoRa telemetry use case does. If you want LoRa's usual long range/robustness instead and don't care about audio, override these back towards 12 / 7.8 kHz – but expect only tens of bits per second at that end, which cannot carry audio at all.

Even at these fast defaults, usable throughput is still only on the order of tens of kbps – nowhere near typical PCM bitrates (8 kHz/8-bit mono alone is 64 kbps) – so audio only becomes practical once reduced to a very low sample rate, 8-bit and/or mono, and ideally compressed before it reaches this stream. Treat this as a fit for short clips or intermittent bursts, not a continuous/live stream; several regions additionally impose legal duty-cycle limits on the ISM bands LoRa uses (e.g. roughly 1% airtime in the EU 868 MHz band) that a sustained stream would likely violate.

Codec recommendation: encode speech with Codec2 (Codec2Encoder / Codec2Decoder in AudioTools/AudioCodecs/CodecCodec2.h) before writing to this stream, and decode it back out after reading. Codec2 was designed for exactly this situation – squeezing intelligible speech over narrowband radio links (it's the codec behind ham radio digital voice modes like FreeDV) – and offers modes from 3200 bit/s down to as low as 450 bit/s. At its 700 bit/s mode, a single ~200 byte LoRa packet carries over 2 seconds of speech, compared to a fraction of a second of raw 8-bit PCM; that's the difference between this being usable for short voice messages and not being usable at all. See the full codec list at https://github.com/pschatzmann/arduino-audio-tools/wiki/Encoding-and-Decoding-of-Audio for alternatives if Codec2 doesn't fit your case (e.g. GSM 06.10 at ~13 kbps if you have more throughput headroom and want wider codec compatibility with other systems).

Heltec LoRa 32 pins (as used by pin_ss/pin_rst/pin_dio0 below): NSS: 8, SCK: 9, MOSI: 10, MISO: 11, RST: 12, BUSY: 13, DIO1: 14

Author

Phil Schatzmann

Copyright

GPLv3

Member Function Documentation

clear()

virtual void clear ( )

inlinevirtualinherited

copyFrom()

void copyFrom ( AudioInfo  info )

inlineinherited

Same as set.

equals()

bool equals ( AudioInfo  alt )

inlineinherited

Returns true if alt values are the same like the current values.

equalsExSampleRate()

bool equalsExSampleRate ( AudioInfo  alt )

inlineinherited

Checks if only the sample rate is different.

logInfo()

virtual void logInfo ( const char *  source = "" )

inlinevirtualinherited

Reimplemented in I2SConfigESP32, I2SConfigESP32V1, I2SConfigStd, and I2SConfigZephyr.

operator bool()

operator bool ( )

inlineinherited

Returns true if all components are defined (no component is 0)

operator!=()

bool operator!= ( AudioInfo  alt )

inlineinherited

Returns true if alt values are the different from the current values.

operator==()

bool operator== ( AudioInfo  alt )

inlineinherited

Returns true if alt values are the same like the current values.

set()

void set ( AudioInfo  info )

inlineinherited

Copies the values from info.

setAudioInfo()

void setAudioInfo ( AudioInfo  info )

inlineinherited

Same as set.

Member Data Documentation

bits_per_sample

uint8_t bits_per_sample = DEFAULT_BITS_PER_SAMPLE

inherited

Number of bits per sample (int16_t = 16 bits)

channels

uint16_t channels = DEFAULT_CHANNELS

inherited

Number of channels: 2=stereo, 1=mono.

frequency

int frequency = 868E6

max_size

int max_size = 200

pin_dio0

int pin_dio0 = 14

pin_rst

int pin_rst = 12

pin_ss

int pin_ss = 8

process_audio_info

bool process_audio_info = true

Send/expect a leading AudioInfo header packet (see AudioLoRa's class doc for how this is used and its single-point-of-failure caveat).

sample_rate

sample_rate_t sample_rate = DEFAULT_SAMPLE_RATE

inherited

Sample Rate: e.g 44100.

signal_bandwidth

int signal_bandwidth

Initial value:

=
      500E3

spi_speed

int32_t spi_speed = 8E6

spreading_factor

int spreading_factor = 6

sync_word

int sync_word = 0xF3

tx_power

int tx_power = 20

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The documentation for this struct was generated from the following file:

• src/AudioTools/Communication/AudioLoRa.h