When you try to compile your C/C++ project (typically a STM32 project):
C:/Users/User/MyProject/MyHeader.h:9:7: error: unknown type name 'size_t'
9 | const size_t MySize = 15;
| ^~~~~~At the top of the file where this error occurs, add the following line:
#include <stddef.h>
Also see the same example for a local serial port: PySerial minimal example: Copy data received from serial port to stdout
This example connects to the RFC2217 remote serial port on 10.1.2.3 port 1234. It does not send data to the serial port but only copies data received from the serial port to stdout.
#!/usr/bin/env python3
import serial
with serial.serial_for_url("rfc2217://10.1.2.3:1234", baudrate=115200) as ser:
try:
while True:
response = ser.read()
if response:
print(response.decode("iso-8859-1"), end="")
finally:
ser.close()
By using iso-8859-1 decoding, we ensure that even binary bytes are decoded in some way and do not cause an exception.
The following command assumes that you have at least one previous tag in the repository:
git describe --long --tags --dirty
Example output:
v0.1.0-9-g68066f4-dirty
This means that we’re on the 9th commit after the v0.1.0 tag with commit ID g68066f4 and the working tree is dirty, i.e. there are uncommited changes.
wget https://packages.microsoft.com/config/ubuntu/22.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb sudo dpkg -i packages-microsoft-prod.deb rm packages-microsoft-prod.deb sudo apt-get update && sudo apt-get install -y dotnet-sdk-7.0
Source for these commands: Microsoft documentation
It is certainly a hassle when you always have to re-configure OpenPnP to open the correct serial device for LumenPnP.
In order to fix, this, we’ll create an alias /dev/lumenpnp that points to /dev/ttyACM0 or /dev/ttyACM1 or any other port that gets assigned to LumenPnP. Create /etc/udev/rules.d/99-lumenpnp.rules:
ACTION=="add", ENV{ID_VENDOR_ID}=="0483", ENV{ID_MODEL_ID}=="5740", SYMLINK+="lumenpnp"
Now, reload udev to activate the rule:
sudo udevadm control --reload-rules && sudo udevadm trigger
Now, open ~/.openpnp2/machine.xml, find this line:
<serial line-ending-type="LF" port-name="ttyACM0" baud="115200" ...
and set port-name to lumenpnp:
<serial line-ending-type="LF" port-name="lumenpnp" baud="115200" ...
After this, you need to restart OpenPnP. Typically, it works without reconnecting the device (due to udevadm trigger). If it doesn’t work, unplug and re-plug the mainboard USB connector.
First, generate a SSH key:
ssh-keygen -t ed25519 -f id_teltonika.pub
Now copy the content of id_teltonika.pub which should look like this:
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICfPyvgFaANpm+vjEcbQSHkmXe27DqLanlB++5+muI7H uli@uli-desktop
and open the Teltonika web interface and open System -> Administration -> Access Control
On that page, set Enable key-based authentication to On. Furthermore, paste the content of id_teltonika.pub into the Public Keys field.
After that remember to click Save & Apply at the bottom of the page!
Now you can login using the public key, e.g.:
ssh -i id_teltonika [email protected]
You can just install pipon OpenWRT such as on the Teltonika RUTX10/RUTX11 or TRB series using opkg:
opkg update opkg install python3-pip
Tested on firmware TRB1_R_00.07.02.6.
If you route all your traffic via a VPN on Linux, you will typically not be able to access local networks except for the network which you are directly connected to via L2.
In order to fix this, you can simply add a route, which typically takes precedence over the VPN route even with additional options.
The following example will add a route to 10.1.2.0/24 (local network) via the gateway=local router we’re connected via L2 to (192.168.1.1)
sudo ip route add 10.1.2.0/24 via 192.168.1.1
This command will move all *.ics files from the current directory and
mkdir -p ICS
find . -name "*.ics" -type f -exec mv --backup=numbered -v {} ICS/ \;Due to --backup=numbered, files with the same name won’t overwrite anything but instead mv will append a number such as ~2~ to the filename.
This command will run sha256sum recursively on all files in a directory:
find . -type f -print0 | xargs -0 sha256sum
You can also pipe it into a file
find . -type f -print0 | xargs -0 sha256sum > recursive-sha256sum.txt
Generally, SMD ferrites of a given size are characterized by:
100 MHz)100 Ω @ 100 MHz) do not filter EMI that well, but also distort your data signals less. Use them for high speed signals above 1 MHz1kΩ @ 100 MHz, filter EMI really well but will distort any high speed signal. Use them for low speed signals below 1 MHz0.1A of current rating to be able to handle soft short circuits20% is typically fine)As with most passive parts, LCSC generally has the lowest pricing if you buy a bunch of parts.
Keep in mind the expensive shipping, but since they are often 50 times cheaper (!) than other distributors, it might be worth it even if just ordering a reel of ferrites.
This section contains cheap SMD ferrite beads for < 1A current rating.
Low impedance (<= 500Ω):
0.0019€/pc@4000pc = 7.60€/reelHigh impedance (>= 500Ω):
0.0026€/pc@4000pcs = 10.40€/reel0.0027€/pc@4000pc = 10.80€/reel0.0044€/pc@4000pc = 17.60€/reel0.01264€/pc@4000pc = 50.56€/reel0.0181€/pc = 72.40€/reelThis section contains cheap SMD ferrite beads for > 1A current rating.
Low impedance (<= 500Ω):
0.006€/pc@4000pc = 24. 00€/reel0.0086€/pc@4000pc = 34.40€/reelHigh impedance (>= 500Ω):
0.0088€/pc@4000pc = 35.20€/reel0.0095€/pc@4000pc = 38.00€/reelI generally use the LTV-356T optocoupler (phototransistor output) for general purpose applications. It has a smaller footprint than most DIP-derived SMD optocouplers and a thinner package. Its pin pitch is 2.54mm whereas the center-distance between the pads is 6.5mm. It it rated
It is available:
0,12€/pc@1kpc0,056€/pc@1kpcThe LTV-356T has the advantage of being available from different sources in large quantities. However, you can get a pin-compatible variant LTV-356T-C which is only rated for 35V on the output:
0,0404€/pc@1kpcAt LCSC, you can also get the half-width OR-3H7B-TP-Gwith a pin pitch of only 1.27mm for 0,0424€/pc@1kpc
Typically, 1% thick film resistors are used as general purpose SMD resistors. Most of these are spec’d with a 100ppm/°C temperature coefficient.
From all the “normal” distributors, in my experience LCSC has by far the cheapest resistors – around 3€ per reel (5000pcs) of 0603 resistors. Note, however, that they charge around 35€ of shipping to Germany. So you have to buy a lot of resistors in order to compensate for the expensive shipping. However, you can also order other components on LCSC (they’re usually quite cheap, especially for passives and other standard components).
0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel0.0006€/pc = 3€/reel
When you try to run dji_irp from the DJI thermal SDK on Linux, you see the following error message:
./utility/bin/linux/release_x64/dji_irp: error while loading shared libraries: libdirp.so: cannot open shared object file: No such file or directory
The libdirp.so library is included with the SDK but it is in a subfolder (the same subfolder where dji_irp is located) where the shell can’t find it.
In order to fix the issue, prefix the command you’re using with
LD_LIBRARY_PATH=./utility/bin/linux/release_x64/
For example:
LD_LIBRARY_PATH=./utility/bin/linux/release_x64/ ./utility/bin/linux/release_x64/dji_irp
This command will look for a line starting with volumes: and remove all lines after said line from the file (including the line starting with volumes: itself).
sed -i -e '/^volumes:/,$d' myfile
The command edits the file in-place (-i), no copy (or backup) of the file will be created.
This will download page 1000 … page 1 in descending order and save the HTML to 1000.html up to 1.html
import requests
for i in range(1000, 0, -1):
with open(f"{i}.html", "w") as outfile:
outfile.write(requests.get(f"https://forum.my-domain.com/showthread.php?123456-my-thread/page{i}").text)import requests
from tqdm import tqdm
for i in tqdm(range(1000, 0, -1)):
with open(f"{i}.html", "w") as outfile:
outfile.write(requests.get(f"https://forum.my-domain.com/showthread.php?123456-my-thread/page{i}").text)
On FreeRTOS on the ESP32, you want to use a critical zone like this:
portENTER_CRITICAL(); // Your critical code goes here! portEXIT_CRITICAL();
but while compiling the procject, you see an error message like
src/main.cpp: In function 'void MyFunc(size_t, int16_t)': /home/uli/.platformio/packages/framework-arduinoespressif32@src-f2ea83e2545300b10a69ff44ef9dc6cd/tools/sdk/esp32/include/freertos/port/xtensa/include/freertos/portmacro.h:476:75: error: too few arguments to function 'void vPortEnterCritical(portMUX_TYPE*)' #define portENTER_CRITICAL(mux) vPortEnterCritical(mux)
You need to use portENTER_CRITICAL() and portEXIT_CRITICAL() with a spinlock, i.e.
portENTER_CRITICAL(&mySpinlock); // TODO Your critical code goes here! portEXIT_CRITICAL(&mySpinlock);
In order to see a full example on how to initialize a spinlock in FreeRTOS and use it for critical zones, see our previous post ESP32 critical zone example using FreeRTOS / PlatformIO
In order to enter a critical zone on the ESP32 using FreeRTOS, you have to do the following:
Globally declare a spinlock:
portMUX_TYPE mySpinlock;
In setup(), initialize the spinlock:
spinlock_initialize(&mySpinlock);
Now, wherever you want to enter a critical zone, run:
portENTER_CRITICAL(&mySpinlock); // TODO Your critical code goes here! portEXIT_CRITICAL(&mySpinlock);
When using this in an interrupt handler, use this instead:
portENTER_CRITICAL_ISR(&mySpinlock); // TODO Your critical code goes here! portEXIT_CRITICAL_ISR(&mySpinlock);
FreeRTOS will ensure that no two threads using mySpinlock are run at the same time.
When trying to compile your Arduino PlatformIO project, you see multiple error messages like the following.
In file included from /home/uli/.platformio/packages/toolchain-xtensa-esp32/xtensa-esp32-elf/sys-include/stdlib.h:19,
from /home/uli/.platformio/packages/toolchain-xtensa-esp32/xtensa-esp32-elf/include/c++/8.4.0/cstdlib:75,
from /home/uli/.platformio/packages/toolchain-xtensa-esp32/xtensa-esp32-elf/include/c++/8.4.0/stdlib.h:36,
from /home/uli/.platformio/packages/framework-arduinoespressif32/cores/esp32/WString.h:26,
from /home/uli/.platformio/packages/framework-arduinoespressif32/cores/esp32/Print.h:26,
from /home/uli/.platformio/packages/framework-arduinoespressif32/libraries/WiFi/src/WiFi.h:27,
from /home/uli/.platformio/packages/framework-arduinoespressif32/libraries/WiFi/src/WiFi.cpp:24:
/home/uli/.platformio/packages/framework-arduinoespressif32/tools/sdk/esp32/include/freertos/port/xtensa/include/freertos/portmacro.h:717:41: error: static assertion failed: portGET_ARGUMENT_COUNT() result does not match for 0 arguments
_Static_assert(portGET_ARGUMENT_COUNT() == 0, "portGET_ARGUMENT_COUNT() result does not match for 0 arguments");For me, the solution was as follows. I had
build_flags = --std=c++17
in my platformio.ini. Replacing it by
build_flags = --std=gnu++17
fixed the issue for me.