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by wjmnelis
Thu Jan 16, 2020 11:39 am
Forum: Beginners
Topic: [Solved] Why is rpi-eeprom also needed on an RPi0W?
Replies: 3
Views: 200

Re: Why is rpi-eeprom also needed on an RPi0W?

Clear. Thanks for the explanation.
by wjmnelis
Thu Jan 16, 2020 11:23 am
Forum: Beginners
Topic: [Solved] Why is rpi-eeprom also needed on an RPi0W?
Replies: 3
Views: 200

[Solved] Why is rpi-eeprom also needed on an RPi0W?

Running `apt-get --just-print upgrade' on an (headless) RPi0W, with Raspbian 10 (buster), shows the following: The following packages will be upgraded: rpi-eeprom rpi-eeprom-images As far as I know only the RPi4 contains EEPROM, and thus an RPi0W does not. Why is it necessary to install the above me...
by wjmnelis
Fri Oct 25, 2019 11:35 am
Forum: Advanced users
Topic: [Solved] With overlay of root, swap does not work
Replies: 3
Views: 1281

Re: With overlay of root, swap does not work

Thanks for the pointer, I did not know of this new feature in raspi-config. However, examining the source code of raspi-config revealed that the upper file system is always a tmpfs, which is created by raspi-config. The upper file system cannot be specified and therefore this function is not a solut...
by wjmnelis
Tue Oct 22, 2019 7:30 pm
Forum: Beginners
Topic: Raspi-config, Overlay file system question...
Replies: 4
Views: 3562

Re: Raspi-config, Overlay file system question...

Thanks for the pointer: I did not know of this new function in raspi-config. However, looking at the overlay part of script raspi-config, it seems that the upper file system is fixed to type 'tmpfs'. The upper file system can not be selected. Thus this is not (part of) a solution for my use-case. Mo...
by wjmnelis
Tue Oct 22, 2019 2:08 pm
Forum: Advanced users
Topic: [Solved] With overlay of root, swap does not work
Replies: 3
Views: 1281

Re: With overlay of root, swap does not work

Well, to answer my question at least partially: use a swap partition in stead of a swap file. I did not succeed in getting swapping to a swap file to work. The swap file, /var/swap, is created but is not used. On a Linux laptop, the overlay partition is resized to free up 2 [GiB]. In this space, a s...
by wjmnelis
Fri Oct 11, 2019 5:40 pm
Forum: Advanced users
Topic: [Solved] With overlay of root, swap does not work
Replies: 3
Views: 1281

[Solved] With overlay of root, swap does not work

Swap does not work if an overlay over the root file system is defined. In order to isolate the changes when compiling and installing a large program, and to extract the (compiled and linked) files needed to install that program on another RPi, an overlay of the root file system was defined. A 32 [Gi...
by wjmnelis
Mon Aug 12, 2019 7:33 pm
Forum: Troubleshooting
Topic: RPi 3B, switching red PWR LED off in rc.local fails
Replies: 3
Views: 162

Re: RPi 3B, switching red PWR LED off in rc.local fails

Well, the solution worked only a few times. Recently both RPi3B computers were upgraded, and a new version of raspbian with kernel 4.19.58-v7+ is installed. After the reboot to activate the new kernel, the original problem was back: the red power LED on the old RPi3B is on, while it is off on the ne...
by wjmnelis
Thu Aug 01, 2019 2:25 pm
Forum: Troubleshooting
Topic: RPi 3B, switching red PWR LED off in rc.local fails
Replies: 3
Views: 162

Re: RPi 3B, switching red PWR LED off in rc.local fails

Thanks for the fast reply. The 'hammering' as proposed does work: both LED's, green and red, are switched off. Then I gradually removed lines, to determine the minimum set of commands needed to switch off both LEDs. The result is: # Switch off the two LEDs of the RPi3. echo 0 > /sys/class/leds/led0/...
by wjmnelis
Thu Aug 01, 2019 1:15 pm
Forum: Troubleshooting
Topic: RPi 3B, switching red PWR LED off in rc.local fails
Replies: 3
Views: 162

RPi 3B, switching red PWR LED off in rc.local fails

I use two RPi 3B computers, both are placed in sight, both are in a transparent casing. In both the file /etc/rc.local contains the following commands at the end: # Switch off the two LEDs of the RPi3. sleep 3 echo 0 > /sys/class/leds/led1/brightness echo 0 > /sys/class/leds/led0/brightness On the o...
by wjmnelis
Sun Feb 10, 2019 6:55 pm
Forum: Advanced users
Topic: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0
Replies: 11
Views: 1239

Re: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0

To answer the implicit question: this is a hobbyist project, to better understand what my central heating system at home is doing and perhaps to control it a little bit.
by wjmnelis
Sun Feb 10, 2019 8:48 am
Forum: Advanced users
Topic: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0
Replies: 11
Views: 1239

Re: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0

It is a big step from writing a Python script to writing and implementing a kernel driver. I'll search for a description and an example, but it feels like a (sub)project with a long and steep learning curve.
by wjmnelis
Sat Feb 09, 2019 10:22 am
Forum: Advanced users
Topic: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0
Replies: 11
Views: 1239

Re: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0

It turned out that changing the parity temporarily from NONE to EVEN caused a problem now and then. If at about the same time a BREAK signal is received from the EMS-bus, it will not be recognised if the parity setting is still EVEN. Note that the parity setting applies to both the transmit and the ...
by wjmnelis
Mon Feb 04, 2019 8:57 am
Forum: Advanced users
Topic: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0
Replies: 11
Views: 1239

Re: How to send a BREAK on the serial device /dev/ttyAMA0

It seems that a break signal is detected by the UART if after all-zero byte the stop-bit is zero instead of one. An additional zero bit can be inserted by sending an all-zero byte with even parity. The following snippets show a way to transmit the shortest possible break signal: import termios attr=...
by wjmnelis
Mon Jan 28, 2019 6:19 pm
Forum: Advanced users
Topic: [Solved] How to send a BREAK on the serial device /dev/ttyAMA0
Replies: 11
Views: 1239

[Solved] How to send a BREAK on the serial device /dev/ttyAMA0

In my current project I would like to write a frame on a two-wire serial bus, called EMS-bus. The protocol prescribes that each frame is terminated by a (short) BREAK. The bus uses asynchronous communication at 9600 [b/s], 8-bit characters, no parity, 1 stop bit. The program is written in Python3, a...
by wjmnelis
Mon Jan 28, 2019 11:41 am
Forum: Advanced users
Topic: [Solved] serial port API documentation
Replies: 13
Views: 2020

[Solved]: serial port API documentation

It has taken quite some time, but after the hardware was delivered and some weeks of programming and testing, there is now a working demonstrator: frames terminated by a BREAK signal on the serial bus can be read, using RPi, raspbian and Python3 code running at user level. The code snippet below sho...
by wjmnelis
Fri Dec 28, 2018 1:54 pm
Forum: Python
Topic: [Solved] queue.Queue looses items
Replies: 2
Views: 211

[Solved] queue.Queue looses items

Issue solved.
In a piece of what I thought to be dead code, there was another invocation of method emsbus.read_frame. This one was responsible for the disappearing frames.
by wjmnelis
Fri Dec 28, 2018 12:35 pm
Forum: Python
Topic: [Solved] queue.Queue looses items
Replies: 2
Views: 211

[Solved] queue.Queue looses items

A RPI0W is used to monitor a bus (asynchronous 9600N1). A multi-threaded Python program is used to read frames from this bus, classify them and write them to a log file.Two types of frames, write_request and write_reply, appear twice per minute on the bus. This sums up to 4 frames per minute, but on...
by wjmnelis
Sat Oct 20, 2018 5:00 pm
Forum: Advanced users
Topic: [Solved] Why does accessing an SHT31-DIS via smbus work?
Replies: 1
Views: 728

Re: Why does accessing an SHT31-DIS via smbus work?

A friendly neighbour has build a simple i2c-sniffer, using an Arduino Mega programmed with the i2c-sniffer-software of R. Richarz (https://github.com/rricharz/i2c-sniffer-100kBaud-Arduino-Mega). Using a 3.3 - 5 Volt level shifter and this sniffer, it is found that the (dummy) register address is wri...
by wjmnelis
Sun Sep 02, 2018 2:17 pm
Forum: Advanced users
Topic: [Solved] serial port API documentation
Replies: 13
Views: 2020

Re: serial port API documentation

Thanks for the pointers. Although anxious to get started, I now have to wait for the hardware (level shifter) to arrive.
by wjmnelis
Sun Sep 02, 2018 1:50 pm
Forum: Advanced users
Topic: [Solved] Why does accessing an SHT31-DIS via smbus work?
Replies: 1
Views: 728

[Solved] Why does accessing an SHT31-DIS via smbus work?

An Adafruit Sensirion SHT31-DIS temperature and humidity sensor is connected, using I2C, to an RPi0W. The latter is running the latest version of Raspbian, and the SHT31 is read using the smbus2.py driver, which is a drop-in replacement for smbus-cffi/smbus-python, and a variant on the Adafruit_SHT....
by wjmnelis
Wed Aug 29, 2018 8:30 am
Forum: Advanced users
Topic: [Solved] serial port API documentation
Replies: 13
Views: 2020

Re: serial port API documentation

A break is a logical zero which lasts longer than one word, thus from start bit up to and including the stop bits. The original question still stands: where can I find some documentation about his "lower level coding", which is hopefully an API. This APi in turn can hopefully be used to extend modul...
by wjmnelis
Sun Aug 19, 2018 2:50 pm
Forum: Advanced users
Topic: [Solved] serial port API documentation
Replies: 13
Views: 2020

Re: serial port API documentation

Yes, it's part of a proprietary standard called EMS, which is the protocol used between in the central heating systems of a few manufacturers, amongst which Nefit.
by wjmnelis
Fri Aug 17, 2018 10:43 am
Forum: Advanced users
Topic: [Solved] serial port API documentation
Replies: 13
Views: 2020

Re: serial port API documentation

The most important I am looking for are ways to handle the reception of a break signal. The only serial Python module I know of is PySerial. With this module, one can send a break, but I've found nothing about receiving a break signal. Perhaps I need to go one level deeper, and use Linux I/O and ioc...
by wjmnelis
Thu Aug 16, 2018 5:29 pm
Forum: Advanced users
Topic: [Solved] serial port API documentation
Replies: 13
Views: 2020

[Solved] serial port API documentation

My next project is to read asynchronous (9600, 8N1) data from a bus. Each message is terminated by a break signal. I hope it will be possible to read messages from the serial async port using Python 3. I have been searching for documentation of the API for the serial port on a Raspberry Pi 0W (or 3B...
by wjmnelis
Sat Apr 28, 2018 8:30 pm
Forum: Troubleshooting
Topic: [Solved] RPi 0 PWM output via RPi.GPIO is not linear
Replies: 4
Views: 702

Re: RPi 0 PWM output via RPi.GPIO is not linear

So what you are saying is that RPi.GPIO does not take advantage of the hardware PWM build in the raspberry? Reanalysis of the measurement, that is not forcing the trend line through (0,0), shows that the output voltage on pin GPIO.18 is about 0.074 [V] too high. If the measurement with a duty cycle ...

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