small fixes; add compile checks

.gitmodules

@@ -14,3 +14,6 @@
 [submodule "gui/source/ImGuiColorTextEdit"]
 	path = gui/source/ImGuiColorTextEdit
 	url = https://github.com/BalazsJako/ImGuiColorTextEdit
+[submodule "gui/kissfft"]
+	path = gui/kissfft
+	url = https://github.com/mborgerding/kissfft

firmware/Makefile

@@ -162,10 +162,10 @@ INCDIR = $(CONFDIR) $(ALLINC) $(TESTINC) \
          source source/periph
 
 # Define C warning options here.
-CWARN = -Wall -Wextra -Wundef -Wstrict-prototypes -pedantic
+CWARN = -Wall -Wextra -Wundef -Wstrict-prototypes -pedantic -Werror
 
 # Define C++ warning options here.
-CPPWARN = -Wall -Wextra -Wundef -pedantic -Wno-volatile
+CPPWARN = -Wall -Wextra -Wundef -pedantic -Wno-volatile -Werror -Wconversion
 
 #
 # Project, target, sources and paths
@@ -217,6 +217,17 @@ include $(RULESPATH)/rules.mk
 # Custom rules
 #
 
+check:
+	cppcheck --std=c++17 --enable=warning,style,performance,portability --force $(shell find source/ -name "*.cpp" -or -name "*.hpp" -or -name "*.c" -or -name "*.h" -type f)
+
+tidy:
+	clang-tidy \
+		-warnings-as-errors=* \
+		--extra-arg=-I --extra-arg=/usr/lib/gcc/arm-none-eabi/13/include/g++-v13 \
+		--extra-arg=-I --extra-arg=/usr/lib/gcc/arm-none-eabi/13/include/g++-v13/arm-none-eabi \
+		$(CPPSRC)
+
 #
 # Custom rules
 ##############################################################################
+

firmware/source/communication.cpp

@@ -223,7 +223,7 @@ void sampleRate(unsigned char *cmd)
 {
     if (EM.assert(USBSerial::read(&cmd[1], 1) == 1, Error::BadParamSize)) {
         if (cmd[1] == 0xFF) {
-            unsigned char r = SClock::getRate();
+            auto r = static_cast<unsigned char>(SClock::getRate());
             USBSerial::write(&r, 1);
         } else {
             auto r = static_cast<SClock::Rate>(cmd[1]);

firmware/source/communication.hpp

@@ -2,7 +2,7 @@
  * @file communication.hpp
  * @brief Manages communication with the host computer.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -17,9 +17,17 @@
 class CommunicationManager
 {
 public:
+    /**
+     * Starts the communication manager thread (threadComm).
+     */
     static void begin();
 
 private:
+    /**
+     * Continuously polls the USB serial connection, handling received commands
+     * as necessary.
+     * Does not return.
+     */
     static void threadComm(void *);
 
     static std::array<char, 4096> m_thread_stack;

firmware/source/conversion.cpp

@@ -156,6 +156,7 @@ void ConversionManager::threadRunner(void *)
                     samples = entry(samples, size);
                     asm("mov sp, %0" :: "r" (sp));
                     volatile auto testRead = *samples;
+                    (void)testRead;
                 } else {
                     // Start execution timer:
                     asm("mov %0, sp; eor r0, r0; svc 2" : "=r" (sp));
@@ -163,6 +164,7 @@ void ConversionManager::threadRunner(void *)
                     // Stop execution timer:
                     asm("mov r0, #1; svc 2; mov sp, %0" :: "r" (sp));
                     volatile auto testRead = *samples;
+                    (void)testRead;
                 } 
             }
 

firmware/source/conversion.hpp

@@ -2,7 +2,7 @@
  * @file conversion.hpp
  * @brief Manages algorithm application (converts input samples to output).
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -27,6 +27,10 @@ constexpr unsigned int CONVERSION_THREAD_STACK_SIZE =
 class ConversionManager
 {
 public:
+    /**
+     * Starts two threads: the privileged monitor thread and the unprivileged
+     * algorithm execution thread.
+     */
     static void begin();
 
     // Begins sample conversion.

firmware/source/elf.h

@@ -2,7 +2,7 @@
  * @file elf.h
  * @brief Defines ELF binary format info.
  *
- * Free to use, written by Clyne Sullivan.
+ * Public domain, written by Clyne Sullivan.
  */
 
 #ifndef STMDSP_ELF_HPP

firmware/source/elfload.hpp

@@ -2,7 +2,7 @@
  * @file elfload.hpp
  * @brief Loads ELF binary data into memory for execution.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -24,9 +24,26 @@ class ELFManager
 public:
     using EntryFunc = Sample *(*)(Sample *, size_t);
     
+    /**
+     * Attempts to parse the ELF binary loaded in the file buffer.
+     * Returns true if successful.
+     */
     static bool loadFromInternalBuffer();
+
+    /**
+     * Returns a function pointer to the loaded ELF's entry point.
+     * Returns nullptr if a valid ELF is not loaded.
+     */
     static EntryFunc loadedElf();
+
+    /**
+     * Returns the address of the ELF file buffer (copy ELF binary to here).
+     */
     static unsigned char *fileBuffer();
+
+    /**
+     * "Unloads" the loaded binary by invalidating the entry pointer.
+     */
     static void unload();
 
 private:

firmware/source/error.hpp

@@ -2,7 +2,7 @@
  * @file error.hpp
  * @brief Tracks and reports non-critical errors.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -31,9 +31,25 @@ class ErrorManager
     constexpr static unsigned int MAX_ERROR_QUEUE_SIZE = 8;
 
 public:
+    /**
+     * Adds the given error to the error queue.
+     */
     void add(Error error);
+
+    /**
+     * If condition is false, add the given error to the error queue.
+     * Returns condition.
+     */
     bool assert(bool condition, Error error);
+
+    /**
+     * Returns true if the error queue is not empty.
+     */
     bool hasError();
+
+    /**
+     * Returns the oldest error queue entry after removing it from the queue.
+     */
     Error pop();
 
 private:

firmware/source/handlers.hpp

@@ -2,7 +2,7 @@
  * @file handlers.hpp
  * @brief Interrupt service routine handlers.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -16,12 +16,15 @@
 
 extern "C" {
 
+// Service call handler ("svc" calls)
 __attribute__((naked))
 void port_syscall(struct port_extctx *ctxp, uint32_t n);
 
+// Handle memory faults possibly caused by the algorithm.
 __attribute__((naked))
 void MemManage_Handler();
 
+// Handle execution faults possibly caused by the algorithm.
 __attribute__((naked))
 void HardFault_Handler();
 

firmware/source/monitor.hpp

@@ -2,7 +2,7 @@
  * @file monitor.hpp
  * @brief Manages the device monitoring thread (status LEDs, etc.).
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -19,9 +19,15 @@
 class Monitor
 {
 public:
+    /**
+     * Starts the monitor thread.
+     */
     static void begin();
 
 private:
+    /**
+     * Updates status LEDs. Does not return.
+     */
     static void threadMonitor(void *);
 
     static std::array<char, THD_WORKING_AREA_SIZE(256)> m_thread_stack;

firmware/source/periph/adc.hpp

@@ -2,7 +2,7 @@
  * @file adc.hpp
  * @brief Manages signal reading through the ADC.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -22,18 +22,47 @@ class ADC
 public:
     using Operation = void (*)(adcsample_t *buffer, size_t count);
 
+    /**
+     * Initializes analog input pins and the microcontoller's ADC peripheral.
+     */
     static void begin();
 
+    /**
+     * Begins continuous ADC sampling triggered by SClock at the set sampling
+     * rate.
+     * @param buffer Pointer to buffer for sample data.
+     * @param count Number of samples that the buffer can hold.
+     * @param operation Handler function to operate on filled half-buffers.
+     */
     static void start(adcsample_t *buffer, size_t count, Operation operation);
+
+    /**
+     * Stops the continuous ADC sampling.
+     */
     static void stop();
 
+    /**
+     * Runs a single conversion on the "alt" inputs (parameter knobs).
+     * @param id The ID of the desired "alt" input (zero or one).
+     * @return The sampled value for the given input.
+     */
     static adcsample_t readAlt(unsigned int id);
 
+    /**
+     * Sets the desired sampling rate for the ADC to operate at.
+     */
     static void setRate(SClock::Rate rate);
+
+    /**
+     * Used to override the handler function for the currently running
+     * conversion.
+     */
     static void setOperation(Operation operation);
 
 private:
+    // ADC driver for signal input.
     static ADCDriver *m_driver;
+    // ADC driver for "alt" inputs.
     static ADCDriver *m_driver2;
 
     static const ADCConfig m_config;

firmware/source/periph/cordic.cpp

@@ -1,3 +1,14 @@
+/**
+ * @file cordic.cpp
+ * @brief Provides mathematical functions for algorithms.
+ *
+ * Copyright (C) 2023 Clyne Sullivan
+ *
+ * Distributed under the GNU GPL v3 or later. You should have received a copy of
+ * the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
 #include "cordic.hpp"
 #include "hal.h"
 

firmware/source/periph/cordic.hpp

@@ -1,11 +1,33 @@
+/**
+ * @file cordic.hpp
+ * @brief Provides mathematical functions for algorithms.
+ *
+ * Copyright (C) 2023 Clyne Sullivan
+ *
+ * Distributed under the GNU GPL v3 or later. You should have received a copy of
+ * the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
 #ifndef CORDIC_HPP_
 #define CORDIC_HPP_
 
+/**
+ * Named after the hardware CORDIC peripheral even though software
+ * implementations may be used.
+ */
 namespace cordic {
+    // Provides pi in case cordic functions require it.
     constexpr double PI = 3.1415926535L;
 
+    /**
+     * Prepares cordic functions for use.
+     */
     void init();
 
+    // mod - Calculates remainder for given fraction.
+    // cos, sin, tan - The trig functions.
+
 #if !defined(TARGET_PLATFORM_L4)
     double mod(double n, double d);
 

firmware/source/periph/dac.hpp

@@ -2,7 +2,7 @@
  * @file dac.hpp
  * @brief Manages signal creation using the DAC.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -18,12 +18,35 @@
 class DAC
 {
 public:
+    /**
+     * Initializes DAC output pins and peripheral.
+     */
     static void begin();
 
+    /**
+     * Begins continuous DAC conversion on the given channel, running at the
+     * current SClock sampling rate.
+     * @param channel Selected output channel (0 = sig. out, 1 = sig. gen.).
+     * @param buffer Buffer of sample data to output.
+     * @param count Number of samples in sample buffer.
+     */
     static void start(int channel, dacsample_t *buffer, size_t count);
+
+    /**
+     * Stops DAC conversion on the given channel.
+     */
     static void stop(int channel);
 
+    /**
+     * Determines if signal generator needs more sample data for streamed
+     * output (i.e. audio file streaming).
+     * @return >0 if samples needed, <0 on initial run.
+     */
     static int sigGenWantsMore();
+
+    /**
+     * Returns true if signal generator is currently running.
+     */
     static int isSigGenRunning();
 
 private:

firmware/source/periph/usbcfg.c

@@ -264,7 +264,6 @@ static const USBEndpointConfig ep2config = {
  * Handles the USB driver global events.
  */
 static void usb_event(USBDriver *usbp, usbevent_t event) {
-  extern SerialUSBDriver SDU1;
 
   switch (event) {
   case USB_EVENT_ADDRESS:

firmware/source/periph/usbserial.hpp

@@ -2,7 +2,7 @@
  * @file usbserial.hpp
  * @brief Wrapper for ChibiOS's SerialUSBDriver.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -17,11 +17,30 @@
 class USBSerial
 {
 public:
+    /**
+     * Prepares for USB serial communication.
+     */
     static void begin();
 
+    /**
+     * Returns true if input data has been received.
+     */
     static bool isActive();
 
+    /**
+     * Reads received input data into the given buffer.
+     * @param buffer Buffer to store input data.
+     * @param count Number of bytes to read.
+     * @return Number of bytes actually read.
+     */
     static size_t read(unsigned char *buffer, size_t count);
+
+    /**
+     * Writes data to serial output.
+     * @param buffer Buffer of output data.
+     * @param count Number of bytes to write.
+     * @return Number of bytes actually written.
+     */
     static size_t write(const unsigned char *buffer, size_t count);
 
 private:

firmware/source/runstatus.hpp

@@ -1,5 +1,4 @@
 // Run status
-//
 enum class RunStatus : char
 {
     Idle = '1',

firmware/source/samplebuffer.cpp

@@ -19,12 +19,12 @@ void SampleBuffer::clear() {
 }
 __attribute__((section(".convcode")))
 void SampleBuffer::modify(Sample *data, unsigned int srcsize) {
-    auto size = srcsize < m_size ? srcsize : m_size;
-    size = (size + 15) & (~15);
+    auto dsize = srcsize < m_size ? srcsize : m_size;
+    dsize = (dsize + 15) & (~15);
 
     m_modified = m_buffer;
     const int *src = reinterpret_cast<const int *>(data);
-    const int * const srcend = src + (size / 2);
+    const int * const srcend = src + (dsize / 2);
     int *dst = reinterpret_cast<int *>(m_buffer);
     do {
         int a = src[0];
@@ -49,12 +49,12 @@ void SampleBuffer::modify(Sample *data, unsigned int srcsize) {
 }
 __attribute__((section(".convcode")))
 void SampleBuffer::midmodify(Sample *data, unsigned int srcsize) {
-    auto size = srcsize < m_size / 2 ? srcsize : m_size / 2;
-    size = (size + 15) & (~15);
+    auto dsize = srcsize < m_size / 2 ? srcsize : m_size / 2;
+    dsize = (dsize + 15) & (~15);
 
     m_modified = middata();
     const int *src = reinterpret_cast<const int *>(data);
-    const int * const srcend = src + (size / 2);
+    const int * const srcend = src + (dsize / 2);
     int *dst = reinterpret_cast<int *>(middata());
     do {
         int a = src[0];

firmware/source/samplebuffer.hpp

@@ -2,7 +2,7 @@
  * @file samplebuffer.hpp
  * @brief Manages ADC/DAC buffer data.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -20,25 +20,79 @@ using Sample = uint16_t;
 constexpr unsigned int MAX_SAMPLE_BUFFER_BYTESIZE = sizeof(Sample) * 8192;
 constexpr unsigned int MAX_SAMPLE_BUFFER_SIZE = MAX_SAMPLE_BUFFER_BYTESIZE / sizeof(Sample);
 
+/**
+ * Manages a buffer of sample data from the ADC or DAC with facilities to
+ * work with separate halves of the total buffer (which is necessary when
+ * streaming data to or from the buffer).
+ */
 class SampleBuffer
 {
 public:
-    SampleBuffer(Sample *buffer);
+    // Manage the sample data memory at 'buffer'.
+    explicit SampleBuffer(Sample *buffer);
 
+    /**
+     * Fill the current buffer with midpoint (2048/0V) values.
+     */
     void clear();
 
+    /**
+     * Copy 'srcsize' samples from 'data' into the first half of the current
+     * buffer. Also do equivalent of setModified().
+     */
     void modify(Sample *data, unsigned int srcsize);
+
+    /**
+     * Copy 'srcsize' samples from 'data' into the second half of the current
+     * buffer. Also do equivalent of setMidmodified().
+     */
     void midmodify(Sample *data, unsigned int srcsize);
+
+    /**
+     * Set modified buffer pointer to first half of the current buffer.
+     */
     void setModified();
+
+    /**
+     * Set modified buffer pointer to second half of the current buffer.
+     */
     void setMidmodified();
+
+    /**
+     * Return pointer to most recently modified buffer portion.
+     * Clears this internal pointer when called.
+     */
     Sample *modified();
 
+    /**
+     * Returns pointer to first half of current buffer.
+     */
     Sample *data();
+
+    /**
+     * Returns pointer to second half of current buffer.
+     */
     Sample *middata();
+
+    /**
+     * Returns uint8_t-casted pointer to the current buffer.
+     */
     uint8_t *bytedata();
 
+    /**
+     * Sets the total working size of the current buffer. Current buffer must
+     * be able to accommodate.
+     */
     void setSize(unsigned int size);
+
+    /**
+     * Returns the current total working size (number of samples).
+     */
     unsigned int size() const;
+
+    /**
+     * Returns the current total working size (number of bytes).
+     */
     unsigned int bytesize() const;
 
 private:

firmware/source/samples.hpp

@@ -2,7 +2,7 @@
  * @file samples.hpp
  * @brief Provides sample buffers for inputs and outputs.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -14,6 +14,8 @@
 
 #include "samplebuffer.hpp"
 
+// Define sample buffers for the input and output signals and the signal
+// generator.
 class Samples
 {
 public:

firmware/source/sclock.hpp

@@ -2,7 +2,7 @@
  * @file sclock.hpp
  * @brief Manages sampling rate clock speeds.
  *
- * Copyright (C) 2021 Clyne Sullivan
+ * Copyright (C) 2023 Clyne Sullivan
  *
  * Distributed under the GNU GPL v3 or later. You should have received a copy of
  * the GNU General Public License along with this program.
@@ -19,6 +19,7 @@
 class SClock
 {
 public:
+    // These are the supported sampling rates. GUI keeps its own enumeration.
     enum class Rate : unsigned int {
         R8K = 0,
         R16K,
@@ -28,11 +29,32 @@ public:
         R96K
     };
 
+    /**
+     * Initializes the sample clock hardware.
+     */
     static void begin();
+
+    /**
+     * Starts the sample rate clock if it is not already running.
+     */
     static void start();
+
+    /**
+     * Indicate that the caller no longer needs the sample clock.
+     * This decrements an internal counter that is incremented by start()
+     * calls; if the counter reaches zero, the clock will actually stop.
+     */
     static void stop();
 
+    /**
+     * Sets the desired sampling rate, used for the next start() call.
+     */
     static void setRate(Rate rate);
+
+    /**
+     * Gets the desired sampling rate (SClock::Rate value) casted to an
+     * unsigned int.
+     */
     static unsigned int getRate();
 
 private:

gui/Makefile

@@ -1,6 +1,8 @@
 CXX = g++
 
 CXXFILES := \
+    kissfft/kiss_fft.c \
+    kissfft/kiss_fftr.c \
     source/serial/src/serial.cc \
     source/imgui/backends/imgui_impl_sdl2.cpp \
     source/imgui/backends/imgui_impl_opengl2.cpp \
@@ -13,7 +15,8 @@ CXXFILES := \
     $(wildcard source/stmdsp/*.cpp) \
     $(wildcard source/*.cpp)
 
-CXXFLAGS := -std=c++20 -O2 \
+CXXFLAGS := -std=c++20 -Og -ggdb -g3 \
+	    -Ikissfft \
             -Isource -Isource/imgui -Isource/stmdsp -Isource/serial/include \
             -Isource/ImGuiColorTextEdit -Isource/ImGuiFileDialog \
             $(shell sdl2-config --cflags) \
@@ -32,7 +35,7 @@ LDFLAGS = $(shell sdl2-config --libs) -lGL -lpthread
 OUTPUT := stmdspgui
 endif
 
-OFILES := $(patsubst %.cc, %.o, $(patsubst %.cpp, %.o, $(CXXFILES)))
+OFILES := $(patsubst %.c, %.o, $(patsubst %.cc, %.o, $(patsubst %.cpp, %.o, $(CXXFILES))))
 
 all: $(OUTPUT)
 

gui/kissfft

@@ -0,0 +1 @@
+Subproject commit 8f47a67f595a6641c566087bf5277034be64f24d

gui/source/device.cpp

@@ -316,7 +316,7 @@ bool deviceConnect()
     return false;
 }
 
-void deviceStart(bool logResults, bool drawSamples)
+void deviceStart(bool fetchSamples)
 {
     if (!m_device) {
         log("No device connected.");
@@ -336,7 +336,7 @@ void deviceStart(bool logResults, bool drawSamples)
         log("Ready.");
     } else {
         m_device->continuous_start();
-        if (drawSamples || logResults || wavOutput.valid())
+        if (fetchSamples || wavOutput.valid())
             std::thread(drawSamplesTask, m_device).detach();
 
         log("Running.");

gui/source/gui_code.cpp

@@ -28,6 +28,7 @@ void codeEditorInit()
 {
     editor.SetLanguageDefinition(TextEditor::LanguageDefinition::CPlusPlus());
     editor.SetPalette(TextEditor::GetLightPalette());
+    editor.SetShowWhitespaces(false);
 }
 
 void codeRenderMenu()

gui/source/gui_device.cpp

@@ -2,7 +2,7 @@
 #include "imgui.h"
 #include "imgui_internal.h"
 #include "ImGuiFileDialog.h"
-
+#include "kiss_fftr.h"
 #include "stmdsp.hpp"
 
 #include <array>
@@ -45,7 +45,7 @@ void deviceLoadAudioFile(const std::string& file);
 void deviceLoadLogFile(const std::string& file);
 void deviceSetSampleRate(unsigned int index);
 void deviceSetInputDrawing(bool enabled);
-void deviceStart(bool logResults, bool drawSamples);
+void deviceStart(bool fetchSamples);
 void deviceStartMeasurement();
 void deviceUpdateDrawBufferSize(double timeframe);
 std::size_t pullFromDrawQueue(
@@ -57,6 +57,7 @@ static std::string sampleRatePreview = "?";
 static bool measureCodeTime = false;
 static bool logResults = false;
 static bool drawSamples = false;
+static bool drawFrequencies = false;
 static bool popupRequestBuffer = false;
 static bool popupRequestSiggen = false;
 static bool popupRequestLog = false;
@@ -74,6 +75,7 @@ void deviceRenderDisconnect()
     measureCodeTime = false;
     logResults = false;
     drawSamples = false;
+    drawFrequencies = false;
 }
 
 void deviceRenderMenu()
@@ -104,7 +106,7 @@ void deviceRenderMenu()
         static std::string startLabel ("Start");
         addMenuItem(startLabel, isConnected, [&] {
                 startLabel = isRunning ? "Start" : "Stop";
-                deviceStart(logResults, drawSamples);
+                deviceStart(logResults || drawSamples || drawFrequencies);
                 if (logResults && isRunning)
                     logResults = false;
             });
@@ -118,7 +120,8 @@ void deviceRenderMenu()
         if (!isConnected || isRunning)
             ImGui::PushDisabled(); // Hey, pushing disabled!
 
-        ImGui::Checkbox("Draw samples", &drawSamples);
+        ImGui::Checkbox("Plot over time", &drawSamples);
+        ImGui::Checkbox("Plot over freq.", &drawFrequencies);
         if (ImGui::Checkbox("Log results...", &logResults)) {
             if (logResults)
                 popupRequestLog = true;
@@ -296,13 +299,16 @@ void deviceRenderWidgets()
 
 void deviceRenderDraw()
 {
-    if (drawSamples) {
-        static std::vector<stmdsp::dacsample_t> buffer;
-        static std::vector<stmdsp::dacsample_t> bufferInput;
-        static auto bufferCirc = CircularBuffer(buffer);
-        static auto bufferInputCirc = CircularBuffer(bufferInput);
+    static std::vector<stmdsp::dacsample_t> buffer;
+    static std::vector<stmdsp::dacsample_t> bufferInput;
+    static std::vector<kiss_fft_scalar> bufferFFTIn;
+    static std::vector<kiss_fft_cpx> bufferFFTOut;
+    static auto bufferCirc = CircularBuffer(buffer);
+    static auto bufferInputCirc = CircularBuffer(bufferInput);
+    static bool drawSamplesInput = false;
+    static kiss_fftr_cfg kisscfg;
 
-        static bool drawSamplesInput = false;
+    if (drawSamples) {
         static unsigned int yMinMax = 4095;
 
         ImGui::Begin("draw", &drawSamples);
@@ -433,6 +439,88 @@ void deviceRenderDraw()
             }
         }
 
+        ImGui::End();
+    } else if (drawFrequencies) {
+        ImGui::Begin("draw", &drawFrequencies);
+
+        ImGui::Text("Time: %0.3f sec", drawSamplesTimeframe);
+        ImGui::SameLine();
+        if (ImGui::Button("-", {30, 0})) {
+            drawSamplesTimeframe = std::max(drawSamplesTimeframe / 2., 0.0078125);
+            deviceUpdateDrawBufferSize(drawSamplesTimeframe);
+        }
+        ImGui::SameLine();
+        if (ImGui::Button("+", {30, 0})) {
+            drawSamplesTimeframe = std::min(drawSamplesTimeframe * 2, 32.);
+            deviceUpdateDrawBufferSize(drawSamplesTimeframe);
+        }
+
+        auto newSize = pullFromDrawQueue(bufferCirc);
+        if (newSize > 0) {
+            buffer.resize(newSize);
+            bufferFFTIn.resize(newSize);
+            bufferFFTOut.resize(newSize);
+            bufferCirc = CircularBuffer(buffer);
+            pullFromDrawQueue(bufferCirc);
+
+            kiss_fftr_free(kisscfg);
+            kisscfg = kiss_fftr_alloc(buffer.size(), false, nullptr, nullptr);
+        }
+
+        std::copy(buffer.begin(), buffer.end(), bufferFFTIn.begin());
+        kiss_fftr(kisscfg, bufferFFTIn.data(), bufferFFTOut.data());
+
+        auto drawList = ImGui::GetWindowDrawList();
+        ImVec2 p0 = ImGui::GetWindowPos();
+        auto size = ImGui::GetWindowSize();
+        p0.y += 65;
+        size.y -= 70;
+        drawList->AddRectFilled(p0, {p0.x + size.x, p0.y + size.y}, IM_COL32_BLACK);
+
+        const auto lcMinor = ImGui::GetColorU32(IM_COL32(40, 40, 40, 255));
+        const auto lcMajor = ImGui::GetColorU32(IM_COL32(140, 140, 140, 255));
+
+        {
+            const float yinc = size.y / 10.f;
+            for (int i = 1; i < 10; ++i) {
+                drawList->AddLine({p0.x, p0.y + i * yinc}, {p0.x + size.x, p0.y + i * yinc}, (i % 2) ? lcMinor : lcMajor);
+            }
+        }
+        {
+            const float xinc = size.x / 10.f;
+            for (int i = 1; i < 10; ++i) {
+                drawList->AddLine({p0.x + i * xinc, p0.y}, {p0.x + i * xinc, p0.y + size.y}, (i % 2) ? lcMinor : lcMajor);
+            }
+        }
+
+        const auto Fs = m_device->get_sample_rate();
+
+        const float di = static_cast<float>(buffer.size() / 2) / size.x;
+        const float dx = std::ceil(size.x / static_cast<float>(buffer.size()));
+        ImVec2 pp = p0;
+        float i = 0;
+        while (pp.x < p0.x + size.x) {
+            unsigned int idx = i;
+            float n = std::clamp(bufferFFTOut[idx].r / Fs / 4.f, 0.f, 1.f);
+            i += di;
+
+            ImVec2 next (pp.x + dx, p0.y + size.y * (1 - n));
+            drawList->AddLine(pp, next, ImGui::GetColorU32(IM_COL32(255, 0, 0, 255)), 2.f);
+            pp = next;
+        }
+
+        const auto mouse = ImGui::GetMousePos();
+        if (mouse.x > p0.x && mouse.x < p0.x + size.x &&
+            mouse.y > p0.y && mouse.y < p0.y + size.y)
+        {
+            char buf[16];
+            drawList->AddLine({mouse.x, p0.y}, {mouse.x, p0.y + size.y}, IM_COL32(255, 255, 0, 255));
+
+            const std::size_t si = (mouse.x - p0.x) / size.x * Fs / 2;
+            snprintf(buf, sizeof(buf), "   %5luHz", si);
+            drawList->AddText(mouse, IM_COL32(255, 0, 0, 255), buf);
+        }
+
         ImGui::End();
     }
 }