Version v0.05j "All it takes to stop the war in Ukraine is a phone call."

• Added two documentation files in /docs.
• Merged iannez pull request "Better use variables/constants". Thank you, excellent work!
• Added iannez as Collaborator at top of file comments.
• Preliminary work on adding EEPROM emulation in Flash to save operating parameters.
• Added "tab delimited data output" mode and commands to switch back and forth between formats.
• Removed (hopefully) all remaining code related to MCP4725 12-bit DAC.
• Better comments and code formatting.

Version v0.05i "Stop the war in Ukraine"

• ST7789 TFT LCD SPI display initial support.
• BMP280 sensor on I2C bus support.
• AHT20 support.
• TM1637 4-digit LED clock display initial support.
• MCP4725 I2C 12-bit DAC deprecated (replaced by 16-bit PWM DAC).
• Program refactoring, better comments, various small bugs fixed.

Version v0.05f

• Added missing Bluetooth OCXO warmup messages.
• OCXO warmup now a separate function from calibration.
• Added countdown for calibration (only reported on USB serial for now).
• Added selectable calibration countdowns (15s or 60s).
• A few comments improved / clarified.

Many thanks to iannezsp, this is basically a manual merge of his latest pull request + a few additions of my own.

Version v0.05e

• Check PWM input value in SP command (must be between 1 and 65535).

Version v0.05d ¨BA.2"

• Manual merge of ST7735 SPI color LCD support by Badwater-Frank.
• Preliminary work to support similar ST7789 SPI color LCD.
• More conditional compilation for MCP4725 I2C 12-bit DAC support.
• Moved setup() and loop() to bottom of source code file.

Version v0.05c

• Adds a command to set a PWM value between 1 and 65535.

Version 0.05b "Omicron"

• Added 2kHz test signal generator on pin PB5.
• Fixed bug in adjustVctlPWM() function which generated two overlapping adjustments when the OCXO frequency would come close to 10,000,000.000. Thanks to Badwater-Frank for the bug squashing.

Version v0.05a

• Now requires STM32 Core version 2.2.0 or later for compilation.
• Fixes small OLED display bug after calibration.
• Fixes compilation bug when GPSDO_MCP4725 is not defined (which is now the default).

Version v0.04h

A simple but effective linear interpolation calibration algorithm is implemented (finally!).
Auto-calibration requires just 30 seconds and adjusts the OCXO frequency to 10MHz +/- 0.1Hz.
The 16-bit PWM software DAC replaces the MCP4725 12-bit I2C DAC module as the preferred solution to generate Vctl, the analog voltage that tunes the OCXO frequency. The frequency locked loop using the 16-bit PWM software DAC can stabilize the OCXO frequency to 10MHz +/- 0.001Hz in a couple of hours (depending on a stable GPS fix).

STM32 GPSDO Version v0.04f

First release in the v0.04 series.
Implements tunnel mode command and operation.
OLED display is now a configuration option, as are all the sensors and the Bluetooth interface.
The u-blox Neo-M8 GPS receiver is now configured for optimized stationary antenna operation and increased "quiet time".
Work started on calibration process, command is implemented,
ongoing work on calibration algorithm.
16-bit PWM DAC tested and approved will replace 12-bit I2C DAC as
default hardware to generate Vctl in future versions.
Improved comments and variables names.
Improved documentation.