27. June 2020

ESP32 erase_flash failed with “Invalid head of packet”

The first step before installing MicroPython to ESP32 is to erase the flash.

I’ve installed all necessary software like esptool, but the flashing was failing with error:

esptool.py --chip esp32 --port /dev/ttyUSB0 erase_flash                                                                                                         ──(Sat,Jun27)─┘
esptool.py v2.8
Serial port /dev/ttyUSB0
Connecting........_____....._____....._____....._____....._____....._____....._____

A fatal error occurred: Failed to connect to ESP32: Invalid head of packet (0x1B)

The solution to the problem is to pres and hold BOOT button. Then start erase command mentioned above.

After the initial erase I was able to flash there MicroPython:

esptool.py --chip esp32 --port /dev/ttyUSB0 --baud 460800 write_flash -z 0x1000 esp32-idf4-20200627-unstable-v1.12-590-g9f911d822.bin

Then it was possible to connect via rshell:

rshell -p /dev/ttyUSB0                                                                                                                                          ──(Sat,Jun27)─┘
Using buffer-size of 32
Connecting to /dev/ttyUSB0 (buffer-size 32)...
Trying to connect to REPL  connected
Testing if ubinascii.unhexlify exists ... Y
Retrieving root directories ... /boot.py/
Setting time ... Jun 27, 2020 20:46:47
Evaluating board_name ... pyboard
Retrieving time epoch ... Jan 01, 2000
Welcome to rshell. Use Control-D (or the exit command) to exit rshell.

/home/georgik/projects/esp32> cd /pyboard/
/pyboard> ls
boot.py
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21. June 2020

Learn to draw with tablet online app

Learning to draw takes time. Here you can find simple online app which can help you with the task.

The current version contains line drawing exercises: vertical line, horizontal line, diagonal line /, diagonal line \, X, Y, circle, half of circle.

It’s possible to draw by mouse, tablet or by touch (e.g. mobile device screen).

Suggestions for improvement are welcome. Feel free to post them to comment section.

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16. February 2020

Unable to upload Xamarin app with C/C++ code to Google Play – solution

After finishing release build of your Android application with Xamarin – Visual Studio 2019 you may experience the following error when uploading the app to Google Play Console:

Warning!
This release is not compliant with Google Play 64-bit requirement.

The following APKS or App Bundles are available to 64-bit devices, 
but they only have 32-bit native code: 1000.

Even when your application contains ARM and ARM64, it might still happen that Google refuses to accept your app and returns just the same error message.

The reason is simple: Google requires that your app with native code bundled as AAB (which is ZIP) contains also libraries for 64-bit platform. It does not matter which architecture.

The error is often caused by building application also for Intel platform because emulators on Intel are faster. There are two options to resolve the issue:

  • remove Intel platform from release build
  • add also 64-bit version for Intel platform to release build

Google is checking each platform and your .so files should be mirrored for 32-bit and 64-bit. If your bundle is not consistent then Google will refuse your application.

To fix this problem open Visual Studio 2019. Click your project in Solution Explorer. Open Properties (ALT+Enter).

Click Android Options, scroll down to Advanced button. Click Advanced button.

Uncheck all Intel platform (or check them all, based on your preference) and click Close.

Press CTRL+S to save changes. Create a new archive of your application (menu Build – Archive…)

Upload the new AAB.

If you don’t know how to switch to AAB, just go back to Android Options. Search for Android Package Format and select ‘bundle’.

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26. December 2019

Build Installer for your Python application – PyInstaller

Do you have your Python application ready? Now it’s time to distribute it. The question is how to bundle it?

One way of bundling Python application into exe/binary file is to use PyInstaller.

You can do it using following commands:

pip install pyinstaller
pyinstaller file_with_main.py

The result will be stored in directory dist. The directory contains one build for the operating system that you’re running.

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22. December 2019

Jenkins Generic Webhook Plugin failed with: Did not find any jobs with GenericTrigger configured

Generic Webhook Plugins allows invoking build of Jenkins job.

First of all, you need to set the token in job configuration.

Go to Build Triggers, check Generic Webhook Triggers.

Jenkins Build Trigger

Set Token e.g. to WEBHOOK-TOKEN.

Invoke curl:

curl http://localhost:8080/generic-webhook-trigger/invoke?token=WEBHOOK-TOKEN

It might happen that job build fails with the message:

{"jobs":null,
"message":"Did not find any jobs with GenericTrigger configured! 
If you are using a token, you need to pass it like ...trigger/invoke?token=TOKENHERE. 
If you are not using a token, you need to authenticate like 
http://user:passsword@jenkins/generic-webhook... "}

To fix the problem make sure that Trigger builds remotely is not checked in job configuration. The token set in this field has priority.

Once the duplicate token is removed the build should be possible to start.

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