When I was in university, I had developed a BLE based UAV controller based on an open source Android BLE library. The library itself is quite easy to use but I decided to develop an Android BLE app with native Android BLE API, which can connect and communicate with BLE GATT devices.

“Swipe down/Pull down to refresh” is a widely used feature in various kinds of apps. Let’s see how can we do that via SwipeRefreshLayout in AndroidX.

When we try to access a serial port device(i.e /dev/ttyUSB0) as a normal user, a Permission denied error will occur. Let’s take a look at permissions for those serial port devices:

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ll /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 0 6月  22 19:28 /dev/ttyUSB0

As we can see, except root user, dialout group also has permissions to those serial port tty devices. Hence, to allow normal user access serial port devices, adding normal user to dialout group will suffice:

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sudo usermod -aG dialout $USER

There are several ways to achieve IPC, shared memory is one of those. In this post, we will try to create shared memory via mmap module in python.

kazam is an easy to use screen record tool for Linux. User can install it via apt install kazam on Debian based distribution. After recording, kazam supports to save as mp4 files, which are 4:4:4 by default. To make it available for typical player on other platform, we can covert it to 4:2:0:

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ffmpeg -i ${original.mp4} -vf format=yuv420p ${new.mp4}

In AndroidX, TabLayout has been extended and moved to package com.google.android.material.tabs.TabLayout. This post will describe how to use TabLayout + ViewPager to create swipe views with tabs in AndroidX.

AWS IoT Getting Started: MQTT sample

SWUpdate is a popular embedded system update framework. I’m trying to bring up a OTA update system on stm32mp1, and this OTA system will base on SWUpdate. This post records steps need to be done to install SWUpdate system into Yocto Linux, and create a single copy image to test it.

Yesterday we found that nfsroot will get crash after systemd-networkd starts:

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nfs: server 192.168.0.101 not responding, still trying

Notes about some useful Yocto debugging commands