Re: Pocket Tutor - hardware update

Ken Kaplan

Thanks for the tips.

On Sun, Jul 19, 2020, 7:59 AM Bruce Hall <bhall66@...> wrote:
Hello Ken

If you are having trouble compiling, there are a few places to look:
a) the STM32 "toolchain".
b) the libraries.
c) the board settings.

For a), I've had the best luck with the toolchain at, as described at the beginning of this video:
The official STM32 toolchain works, but the display speed suffers horribly.

The libraries I use are from Adafruit.   If you get an error related to one of the libraries, it could be an incompatible version.
I am using recent versions.  Probably not the most recent.  I will get you version numbers if this proves to be the problem.

Double-check your board settings & make sure they correspond to what I list in the builder's guide.

Did you try compiling your way through the software tutorials, which start at   If you can't find any issue with your settings, go sequentially through the software tutorials (which start with blink) and see where the compiler error pops up.  That should help you narrow down where the problem lies.

You can avoid the Arduino IDE and compiler altogether by flashing your chip with the binaries.   I really like ST-LINK.
One word of advice: make sure you power your device before connecting a ST-LINK clone.  And disconnect the dongle before you switch off your device.  If you don't, the device will consume current from ST-LINK and eventually burn out its tiny 3.3V power regulator.  I burned out a few before I figured out the problem.


On Sat, Jul 18, 2020 at 10:27 PM Ken Kaplan <wb2art@...> wrote:
Okay,  I'll review this when I get to the build.
I will go over the parts list tomorrow. 
Probably build at least 2 units.
Got my st- link today. Have yet to try it.
I did have some trouble compiling the ino a few days ago. I could compile a simple blink program for the stm32,  but try your software,  it said I could not compile for the stm32.  I have tried this on 2 different computers, and got the same result. I most likely have some thing set wrong
 I'll look into it in the next few days.

On Sat, Jul 18, 2020, 6:29 PM Bruce Hall <bhall66@...> wrote:

Excellent!  I hope you enjoy your build as much as I did.

One last thing:  I've been using headphones a lot with my Pocket Tutor.   If you intend to use headphones too, you will notice that output from the external speaker jack can be overwhelming.  (It creates room-filling sound with a 2W speaker.)   Will you get to the audio circuit, there are a few options to consider:

a) Use the circuit as is, and keep the volume control near zero.   It works, but you can do better.  

b)  Increase R13 to a larger value  (Easy fix, but reduces the range of the on-board speaker); or

c)  Add a series resistor between the amplifier circuit and the S-pin (sleeve) of the speaker jack.  This is mechanically trickier to do, but will be more satisfying.  I suggest a value of around 150-330 ohms.  With my headphones, 150 ohms is about right.

d) Make a short adapter cable with a series resistor in it.   Easy but clunky.


On Sat, Jul 18, 2020 at 5:28 PM Ken Kaplan <wb2art@...> wrote:
Yes, I just printed the shared cart.
Will take some time and see if I need to adjust anything.
Ordered the boards from jclpcb. 

On Sat, Jul 18, 2020, 5:18 PM Bruce Hall <bhall66@...> wrote:

I put a shared cart on the builder's guide, which will create a single DigiKey order for most of the parts.   
When I order I get lots of extras, so please review and adjust the quantities of each item you want.  Of course, if you prefer Mouser or another distributor, you will need to order them separately.


On Sat, Jul 18, 2020 at 5:04 PM Ken Kaplan <wb2art@...> wrote:
Thanks for the hints.
I'm going to get boards and parts ordered, probably tomorrow.

On Sat, Jul 18, 2020, 4:59 PM Bruce Hall <bhall66@...> wrote:
I have a few tips for anyone building the Pocket Tutor:

1.  The power supply needs a decoupling capacitor across the battery.  You should solder an additional 10uF cap across the pins of the battery jack J1.

2.  The audio and key jacks are recessed by about a millimeter.  Normally this isn't a problem, but one my plugs fails to make good contact.   So, when soldering these jacks, please situate them as close as possible to the board edge.  The extra-large soldering pads give you some leeway.

I updated the builder's guide to reflect these two changes.


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