Re: Morse tutor

Bruce Hall

Hello John,

Nice to hear from you again!

I have all of the software on GitHub.  I updated the software for the 'old' tutor, which is here:

The display updates will work on your old STM32 device, except for backlight control.    I have not updated the ESP32 code yet.

For backlight control, the old tutor requires a hardware change.  The first step in the procedure is to look at the back of the display pcb, where the components are mounted, and determine if there is a driver transistor for the backlight circuit.  It will consist of a 3-pin transistor (SOT23 package) and adjacent 1K resistor.  I have discovered that some displays have this driver.  Other displays connect the backlight LEDs directly to the backlight pin.  If you need help locating this transistor I can send you a photo of it.

The new code controls the backlight by varying the duty cycle of a PWM signal.   If there is a transistor driver, we can solder a single wire from the PWM signal to the backlight pin and we are done.   If there is no transistor driver on-board, the backlight current (about 90mA) is too much for the.microcontroller to handle.   In that case we would need to add our own transistor driver.   The pocket tutor pcb has a transistor driver, which can be bypassed if not needed.

Does that help at all?   


On Sun, Jul 19, 2020 at 5:37 AM John Kristiansen <john.k@...> wrote:
Hello Bruce

You did it again! Nice work with the portable tutor and the documentation. Top class!
I hope to get the new software implemented to my 'old' tutor, and need a hint for the display improvement. Can I find it in your Githup account?

BR OZ1QZ / John

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