This Clock Generator circuit is particularly suited for Arduino and STM32 user’s but it can serve an electronician in any kind of situation with:

• Up to 3 clocks
• All clocks up to 100 MHz and one clock up to 225 MHz
• Settable signal strength
• Settable phase
• Easy interface
• Programmable / remote controllable

It is build around the well known Si5351 chip by Silicon Labs, driven by an STM32 Cortex m3 microcontroller. The need for this tool came from the fact that I use a couple of microcontroller and often experiment start-up problems. In some situation the MCU is bricked and I need an external clock (for example a 1 MHz clock for the Atmega328p), or I implemented an oscillator with the wrong clock frequency, or I you would like to check the frequency tolerance of a chip. Typical applications are:

• bricked MCUs
• testing different frequency settings to clock an MCU or another device
• wrong clock needs an immediate replacement for prototyping
• multi clock systems (for example the Clock Generator needs one 8 MHz clock and one 25 to 27 MHz clock)
• testing the frequency tolerance / operating range of a chip
• very high frequency clock
• frequency sweep on small and very large ranges
• radio variable oscillator source
• signals in phase opposition or in phase quadrature …

User interface Very clear and simple user interface with a color TFT 1.8″ display, a selector and one menu button. All actions are done by rotating the selector, single clicking or pressing the button.

Clock settings - 3 clocks

• From 2.5 KHz to 100 MHz and 225 MHz on one clock.

• Relative phase adjustment for two clocks as compared to a reference clock. The phase steps depend on the respective frequencies of the clocks. Allows phase opposition and quadrature of two or three clocks at the same frequency.

• 4 drive strength levels: allows proper propagation or reduction of the ringing of the signal.

Please note that this module is not a function generator. It goes up to the VHF range but the signal shape goes from totally square to squarrish to plus or minus sinusoidal when the frequency goes up. It depends in part of the impedance matching between the output and the load. So the drive settings is usefull to get the best shape depending on the conditions.

• One click status setting: turn on clock / turn off clock / invert phase.

• The main screen shows for each clock: frequency, drive strength, phase, status.

Store clock settings Store or restore 2 sets of all 3 clocks parameters.

Frequency sweep Allows to sweep frequencies by setting

• Start and stop frequencies
• Frequency steps
• Sweep period
• All 3 clocks can sweep (nearly) simultaneously.

Programmable The device can be programmed in the Arduino environment. So you can use the Clock Generator for example in a tool chain to check the response of a system. The minimum program structure is extremely bare:

Remote controled You can also set the clock parameters by sending commands over I2C or Serial. Here is an example of sending commands from the Arduino IDE Serial Monitor

Read the full description here

Here are the resources, code exemples etc...