logic_analyzer::CaptureESP32I2S Class Reference

Hardware-timed 8 bit parallel GPIO capture for the original ESP32, using the I2S0 peripheral's undocumented "camera" (LCD) mode + DMA - the same trick used by the esp32-camera driver and by the EUA/ESP32_LogicAnalyzer project (both credited below) to sample a parallel bus with zero CPU involvement per sample. More...

#include <capture_esp32_i2s.h>

Inheritance diagram for logic_analyzer::CaptureESP32I2S:

Public Member Functions
	CaptureESP32I2S (int pinStart=19, int clkOutPin=32, int clkInPin=34)
	Default Constructor - uses GPIO19..GPIO26 as the 8 bit data bus.
void	setDataPins (const int pins[8])
	Defines the 8 data pins individually if they are not contiguous.
void	capture () override
	starts the capturing of the data
void	captureAll () override
	Used to measure the speed - capture into memory w/o dump.
float	frequencyMeasured ()
	Provides the measured capturing frequency (based on the last capture)
Public Member Functions inherited from logic_analyzer::AbstractCapture
	AbstractCapture ()
	Default Constructor.
	~AbstractCapture ()
	Destructor.
LogicAnalyzer &	logicAnalyzer ()
	Provides access to the LogicAnalyzer.
virtual PinReader &	pinReader ()
	Provides access to the PinReader.
virtual void	setStatus (Status status)
	Sets the status.

Protected Member Functions
void	setupOnce ()
	One-time GPIO/I2S peripheral setup.
void	allocDma (uint32_t sampleCount)
	(Re)allocates the DMA descriptor chain for the requested sample count
void	freeDma ()
void	enableSampleClock (uint32_t freqHz)
	Drives the sample clock via LEDC PWM on clk_out_pin, looped back into clk_in_pin.
void	start ()
void	waitForResult ()
void	dump ()
Protected Member Functions inherited from logic_analyzer::AbstractCapture
virtual void	setLogicAnalyzer (LogicAnalyzer &la)

Static Protected Member Functions
static void	gpioSetupIn (int gpio, int sig)
static void	i2sConfReset ()

Protected Attributes
int	data_pins [8]
int	clk_out_pin
int	clk_in_pin
uint32_t	n_samples = 0
unsigned long	start_time = 0
unsigned long	run_time_us = 0
bool	is_setup = false
lldesc_t *	dma_desc = nullptr
uint8_t **	dma_buf = nullptr
size_t	dma_desc_count = 0
Protected Attributes inherited from logic_analyzer::AbstractCapture
LogicAnalyzer *	logic_analyzer_ptr = nullptr

Static Protected Attributes
static const size_t	desc_size = 2000

Detailed Description

Hardware-timed 8 bit parallel GPIO capture for the original ESP32, using the I2S0 peripheral's undocumented "camera" (LCD) mode + DMA - the same trick used by the esp32-camera driver and by the EUA/ESP32_LogicAnalyzer project (both credited below) to sample a parallel bus with zero CPU involvement per sample.

Unlike the RP2040 PIO, the ESP32's I2S0 can only be driven by an external clock in this mode (I2S0.conf.rx_slave_mod = 1) - it does not sample on its own internal clock. So this class generates the sample clock itself with the LEDC PWM peripheral on clk_out_pin and expects it to be looped back with a jumper wire into clk_in_pin, which is configured as the I2S input clock. Default pins: clk_out=GPIO32 -> jumper -> clk_in=GPIO34.

Data pins default to GPIO19..GPIO26 (8 bits), matching START_PIN/PIN_COUNT in config_esp32.h.

This capture path does not support triggering (same limitation as PicoCapturePIO) - it always captures readCount samples starting immediately on arm.

Credit: register sequence adapted from https://github.com/EUA/ESP32_LogicAnalyzer (GPLv3) and https://github.com/igrr/esp32-cam-demo

Author

Phil Schatzmann

Copyright

GPLv3

Member Function Documentation

capture()

void logic_analyzer::CaptureESP32I2S::capture ( )

inlineoverridevirtual

starts the capturing of the data

Implements logic_analyzer::AbstractCapture.

captureAll()

void logic_analyzer::CaptureESP32I2S::captureAll ( )

inlineoverridevirtual

Used to measure the speed - capture into memory w/o dump.

Implements logic_analyzer::AbstractCapture.

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

• src/capture_esp32_i2s.h