TinyView — Principles and API¶

OVERVIEW¶

The support module includes four main functions:

1. Signal Visualization: Plot signals in ASCII format (like an oscilloscope)
2. Spectrum Visualization: Visualize power spectra with frequency axis labels
3. Array Printing: Print arrays in formatted tables
4. Statistics: Calculate and display statistical information about signals

SIGNAL VISUALIZATION¶

tiny_view_signal_f32¶

/**
 * @name: tiny_view_signal_f32
 * @brief Visualize a signal in ASCII format (like oscilloscope)
 * @param data Input signal array
 * @param len Length of the signal
 * @param width Width of the plot in characters (default: 64)
 * @param height Height of the plot in lines (default: 16)
 * @param min Minimum Y-axis value (auto-detect if min == max)
 * @param max Maximum Y-axis value (auto-detect if min == max)
 * @param title Optional title for the plot (NULL for no title)
 * @return tiny_error_t
 */
tiny_error_t tiny_view_signal_f32(const float *data, int len, int width, int height, float min, float max, const char *title);

Description:

Visualizes a signal in ASCII format, similar to an oscilloscope display. The function creates a character-based plot showing the signal waveform.

Features:

• High-resolution drawing with linear interpolation between data points

• Automatic Y-axis range detection when min == max

• Customizable plot dimensions (width and height)

• Optional title display

• Y-axis labels showing value range

• X-axis labels showing sample indices

Parameters:

• data: Pointer to the input signal array.

• len: Length of the signal array.

• width: Width of the plot in characters (typically 64).

• height: Height of the plot in lines (typically 16).

• min: Minimum Y-axis value. If min == max, the function will auto-detect the range.

- max: Maximum Y-axis value. If min == max, the function will auto-detect the range.¶

• title: Optional title string for the plot. Pass NULL for no title.

Return Value:

Returns success or error code.

Output Format:

The function prints:

• Title (if provided)

• Y-axis labels with value range

• ASCII plot with '*' characters representing the signal

• X-axis with sample index labels

• Summary line with value range and signal length

Example Output:

Test Signal: 10 Hz Sine Wave
Value
  1.20 |                                        
  1.00 |                                        
  0.80 |                                        
  0.60 |                                        
  0.40 |                                        
  0.20 |                                        
  0.00 |                                        
 -0.20 |                                        
 -0.40 |                                        
 -0.60 |                                        
 -0.80 |                                        
 -1.00 |                                        
 -1.20 |                                        
       ------------------------------------------------------------------------
       0        8       16      24      32      40      48      56 (Sample Index)
Range: [-1.200, 1.200], Length: 64

SPECTRUM VISUALIZATION¶

tiny_view_spectrum_f32¶

/**
 * @name: tiny_view_spectrum_f32
 * @brief Visualize power spectrum in ASCII format (optimized for frequency domain)
 * @param power_spectrum Power spectrum array
 * @param len Length of the spectrum
 * @param sample_rate Sampling rate (Hz) for frequency axis labels
 * @param title Optional title for the plot (NULL for no title)
 * @return tiny_error_t
 */
tiny_error_t tiny_view_spectrum_f32(const float *power_spectrum, int len, float sample_rate, const char *title);

Description:

Visualizes a power spectrum in ASCII format with frequency axis labels. The function creates a bar chart showing the power at different frequencies.

Features:

• Bar chart visualization (vertical bars)

• Automatic frequency axis labeling based on sample rate

• Optimized for frequency domain data (uses first half of spectrum)

• Frequency labels in Hz

• Nyquist frequency indication

Parameters:

• power_spectrum: Pointer to the power spectrum array.

• len: Length of the power spectrum array.

• sample_rate: Sampling rate of the original signal in Hz (used for frequency axis labels).

• title: Optional title string for the plot. Pass NULL for no title.

Return Value:

Returns success or error code.

Output Format:

The function prints:

• Title (if provided)

• Y-axis labels with power values

• ASCII bar chart with '|' characters

• X-axis with frequency labels in Hz

• Summary line with value range and Nyquist frequency

Note:

The function assumes the power spectrum length is half of the FFT length (typical for real signals). Frequency labels are calculated as: freq = index * sample_rate / (2 * len).

ARRAY PRINTING¶

tiny_view_array_f32¶

/**
 * @name: tiny_view_array_f32
 * @brief Print array values in a formatted table
 * @param data Input array
 * @param len Length of the array
 * @param name Name/label for the array
 * @param precision Number of decimal places (default: 3)
 * @param items_per_line Number of items per line (default: 8)
 * @return tiny_error_t
 */
tiny_error_t tiny_view_array_f32(const float *data, int len, const char *name, int precision, int items_per_line);

Description:

Prints array values in a formatted table with customizable precision and items per line.

Features:

• Formatted table output with index labels

• Customizable precision (decimal places)

• Customizable items per line

• Optional array name/label

Parameters:

• data: Pointer to the input array.

• len: Length of the array.

• name: Optional name/label for the array. Pass NULL for default label.

• precision: Number of decimal places to display. If negative, defaults to 3.

• items_per_line: Number of items to print per line. If ≤ 0, defaults to 8.

Return Value:

Returns success or error code.

Output Format:

The function prints:

• Array name and length

• Formatted table with index labels and values

Example Output:

Test Signal [64 elements]:
  [  0] 0.000  0.063  0.125  0.188  0.250  0.313  0.375  0.438 
  [  8] 0.500  0.563  0.625  0.688  0.750  0.813  0.875  0.938 
  ...

STATISTICS¶

tiny_view_statistics_f32¶

/**
 * @name: tiny_view_statistics_f32
 * @brief Print statistical information about a signal
 * @param data Input signal array
 * @param len Length of the signal
 * @param name Name/label for the signal
 * @return tiny_error_t
 */
tiny_error_t tiny_view_statistics_f32(const float *data, int len, const char *name);

Description:

Calculates and prints statistical information about a signal, including min, max, mean, standard deviation, variance, and peak values.

Features:

• Single-pass calculation (efficient)

• Comprehensive statistics:

• Minimum and maximum values with indices
• Peak value (absolute maximum) with index
• Mean (average)
• Standard deviation
• Variance

• Range (max - min)

• Optional signal name/label

Parameters:

• data: Pointer to the input signal array.

• len: Length of the signal array.

• name: Optional name/label for the signal. Pass NULL for default label.

Return Value: Returns success or error code.

Output Format:

The function prints:

• Statistics header with signal name

• All calculated statistics in a formatted table

Example Output:

=== Statistics: Test Signal ===
  Length:     64 samples
  Min:        -1.200000 (at index 48)
  Max:         1.200000 (at index 16)
  Peak:        1.200000 (at index 16)
  Mean:        0.000000
  Std Dev:     0.707107
  Variance:    0.500000
  Range:       2.400000
========================

Mathematical Formulas:

• Mean: \( \mu = \frac{1}{N} \sum_{i=0}^{N-1} x[i] \)

• Variance: \( \sigma^2 = \frac{1}{N} \sum_{i=0}^{N-1} x[i]^2 - \mu^2 \)

• Standard Deviation: \( \sigma = \sqrt{\sigma^2} \)

• Range: \( \text{range} = \max(x) - \min(x) \)

USAGE WORKFLOW¶

Typical Visualization Workflow¶

1. Visualize Signal:

   float signal[64];
   // ... fill signal with data ...
   tiny_view_signal_f32(signal, 64, 64, 16, 0, 0, "My Signal");
   

2. Print Array:

   tiny_view_array_f32(signal, 64, "Signal Data", 3, 8);
   

3. Show Statistics:

   tiny_view_statistics_f32(signal, 64, "Signal");
   

4. Visualize Spectrum:

   float power[128];
   // ... calculate power spectrum ...
   tiny_view_spectrum_f32(power, 128, 1000.0f, "Power Spectrum");
   

APPLICATIONS¶

The support module is useful for:

• Debugging: Visualize signals during algorithm development

• Analysis: Quick statistical analysis of signals

• Education: Demonstrate signal processing concepts

• Embedded Systems: Debug DSP algorithms without graphical displays

• Testing: Verify signal processing results

• Documentation: Generate ASCII plots for documentation

NOTES¶

• All visualization functions output to stdout using printf

• The ASCII plots are designed for monospace fonts

• For best results, use a terminal with at least 80 characters width

• Signal visualization uses linear interpolation for smooth plots

• Spectrum visualization uses bar charts optimized for frequency domain data