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NanoVNA-H NanoVNA-H Documentation

Flash Memory Layout

Reference for the flash memory layout used to store calibration data and device configuration.

Overview

Section titled “Overview”

NanoVNA-H stores persistent data in on-chip flash memory:

  • Calibration data (properties_t): Sweep settings and calibration coefficients
  • Configuration data (config_t): Device settings and color palette

Data is stored at the end of flash, leaving room for firmware at the beginning.

Memory Maps

Section titled “Memory Maps”

STM32F072xB Flash Layout

Address RangeSizeContent
0x08000000 - 0x0801BFFF112 KBFirmware code
0x0801C000 - 0x0801D7FF6 KBProperty slot 0
0x0801D800 - 0x0801EFFF6 KBProperty slot 1
0x0801F000 - 0x080207FF6 KBProperty slot 2
0x08020800 - 0x08021FFF6 KBProperty slot 3
0x08022000 - 0x080237FF6 KBProperty slot 4
0x08023800 - 0x08023FFF2 KBConfiguration

Constants:

#define FLASH_START_ADDRESS    0x08000000
#define FLASH_TOTAL_SIZE       (128*1024)   // 131072 bytes
#define FLASH_PAGESIZE         0x800        // 2048 bytes


#define SAVEAREA_MAX           5            // 5 calibration slots
#define SAVE_CONFIG_SIZE       0x00000800   // 2 KB config
#define SAVE_PROP_CONFIG_SIZE  0x00001800   // 6 KB per property

Address Calculation

Section titled “Address Calculation”

The save area starts at the end of flash:

// Total save area size
#define SAVE_FULL_AREA_SIZE  (SAVE_CONFIG_SIZE + SAVEAREA_MAX * SAVE_PROP_CONFIG_SIZE)


// Configuration address (at very end)
#define SAVE_CONFIG_ADDR     (FLASH_START_ADDRESS + FLASH_TOTAL_SIZE - SAVE_CONFIG_SIZE)


// Properties start address (before config)
#define SAVE_PROP_CONFIG_ADDR (FLASH_START_ADDRESS + FLASH_TOTAL_SIZE - SAVE_FULL_AREA_SIZE)

F072 Calculations

Section titled “F072 Calculations”
SAVE_FULL_AREA_SIZE  = 0x800 + 5 * 0x1800 = 0x7800 (30 KB)
SAVE_CONFIG_ADDR     = 0x08000000 + 0x20000 - 0x800 = 0x0801F800
SAVE_PROP_CONFIG_ADDR = 0x08000000 + 0x20000 - 0x7800 = 0x08018800

F303 Calculations

Section titled “F303 Calculations”
SAVE_FULL_AREA_SIZE  = 0x800 + 7 * 0x4000 = 0x1C800 (114 KB)
SAVE_CONFIG_ADDR     = 0x08000000 + 0x40000 - 0x800 = 0x0803F800
SAVE_PROP_CONFIG_ADDR = 0x08000000 + 0x40000 - 0x1C800 = 0x08023800

properties_t Storage

Section titled “properties_t Storage”

Each calibration slot stores a complete properties_t structure.

Structure Size

Section titled “Structure Size”
TargetSWEEP_POINTS_MAX_cal_data sizeTotal size
F0721014,040 bytes~5 KB
F30340116,040 bytes~17 KB

Calibration Data Layout

Section titled “Calibration Data Layout”
float _cal_data[CAL_TYPE_COUNT][SWEEP_POINTS_MAX][2];
Cal TypeIndexDescription
CAL_LOAD050 ohm load measurement
CAL_OPEN1Open circuit measurement
CAL_SHORT2Short circuit measurement
CAL_THRU3Through connection measurement
CAL_ISOLN4Isolation measurement

Each entry stores complex data: [0] = real, [1] = imaginary.

config_t Storage

Section titled “config_t Storage”

Configuration is stored in a single 2 KB area.

Structure Contents

Section titled “Structure Contents”
FieldSizeDescription
magic4CONFIG_MAGIC (0x434f4e56)
_harmonic_freq_threshold4Harmonic mode threshold
_IF_freq4IF frequency offset
_touch_cal[4]8Touch calibration corners
_vna_mode2Mode flags
_dac_value2DAC output value
_vbat_offset2Battery voltage offset
_bandwidth2Default bandwidth setting
_lever_mode1Lever control mode
_brightness1LCD brightness (F303)
_lcd_palette[32]64Color palette
_serial_speed4USART baud rate
_xtal_freq4TCXO frequency
_measure_r4Reference impedance
_band_mode1Band selection
_reserved[3]3Reserved
checksum4Data integrity check

Magic Numbers

Section titled “Magic Numbers”
#define CONFIG_MAGIC      0x434f4e56  // "CONV" - Config
#define PROPERTIES_MAGIC  0x434f4e54  // "CONT" - Properties

When loading data:

  1. Check magic value matches expected
  2. Verify checksum
  3. If either fails, use defaults

Flash Operations

Section titled “Flash Operations”

Writing Data

Section titled “Writing Data”

Flash memory requires erasing before writing. The erase granularity is one page (2 KB).

// Erase pages at address
void flash_erase_pages(uint32_t page_address, uint32_t size);


// Write data (must be erased first)
void flash_program_half_word_buffer(uint16_t* dst, uint16_t *data, uint16_t size);

Save Sequence

Section titled “Save Sequence”
  1. Calculate checksum of data
  2. Erase required flash pages
  3. Write data in 16-bit half-words
  4. Verify write completed

Recall Sequence

Section titled “Recall Sequence”
  1. Read magic value
  2. If magic matches, verify checksum
  3. Copy data to RAM structure
  4. If verification fails, return error

Save/Recall Commands

Section titled “Save/Recall Commands”

Shell Commands

Section titled “Shell Commands”
CommandAction
save <n>Save to slot n (0-4 or 0-6)
recall <n>Load from slot n
saveconfigSave configuration
clearconfigReset configuration
Section titled “Menu Access”

Save: CAL > SAVE > slot number Recall: CAL > RECALL > slot number

Linker Script Configuration

Section titled “Linker Script Configuration”

The linker script reserves flash for storage.

F072 (STM32F072xB.ld)

Section titled “F072 (STM32F072xB.ld)”
MEMORY
{
  flash0 : org = 0x08000000, len = 112K  /* Firmware */
  flash7 : org = 0x0801C000, len = 16K   /* Reserved for storage */
  ...
}

F303 (STM32F303xC.ld)

Section titled “F303 (STM32F303xC.ld)”
MEMORY
{
  flash0 : org = 0x08000000, len = 128K  /* Firmware */
  flash7 : org = 0x08020000, len = 128K  /* Reserved for storage */
  ...
}

Data Recovery

Section titled “Data Recovery”

If configuration becomes corrupted:

  1. From menu: CONFIG > EXPERT SETTINGS > CLEAR CONFIG
  2. From shell: clearconfig command
  3. Hardware reset: Hold BOOT0 during power-on, reflash firmware

Flash Wear Considerations

Section titled “Flash Wear Considerations”

STM32 flash has limited write cycles (~10,000 per page).

Best practices:

  • Avoid excessive saves during development
  • Use saveconfig sparingly
  • Calibration rarely changes, so wear is minimal
  • If flash fails, the page may become read-only