I’m planning to use FM24CL16 EEPROMs in some projects. These are simple I2C EEPROMs but based on FRAM technology so they should last 10^14 of writes while typical 24Cxx chips only last one million. They are much cheaper on aliexpress than at my local distributor so I ordered 5pcs from this seller for about 40 cents each. Since my local distributor sells them 5 times more expensive I was a little bit suspicious if these are legit parts so I decided to test them.
Continue reading Testing chinese FRAMs
Playing with CAN bus
I got inspired by comma.ai – it’s a HW device which will drive your car, pretty much like Tesla does but for a fraction of it’s price. For this, it needs to connect to CAN bus of your car. My current car cannot be driven by wire but it has some simple CAN buses so I decided to have a little play with one of them, just to explore the technology. Continue reading Playing with CAN bus
Emulating HDMI connection
If you want to play with HDMI signals or just emulate a connected display for whatever reason, you need to fool your videocard to think something is really connected.
Continue reading Emulating HDMI connectionEnable system site packages in virtualenv
I started using virtualenv for all python apps I run (because I hate to make mess with pip in system site-packages). Later I’ve found out that some dependencies can not be installed via pip but are included in standard system packages installed via apt or yum. To use these imports inside your venv, you need to specify parameter –system-site-packages when creating your venv. If you only find out that you really need them later, you can enable them by deleting following file:
your_venv_dir/lib/pythonXXX/no-global-site-packages.txt
Happy pythoning!
Source: https://virtualenv.pypa.io/en/latest/userguide/#the-system-site-packages-option
My unbiased experience with JLCPCB
I needed to fabricate some PCBs. I’ve seen some youtubers to advertise and recommend this service so I decided to give it a try. My order was done without using any affiliation link or discount code so there was no way for them to know who I am. I needed to create a microSD breakout board and luckily I found a similar OSHw project and only made some modifications: https://github.com/danielkucera/MicroSD_Sniffer . I prepared my board in Eagle and generated gerber files. Continue reading My unbiased experience with JLCPCB
Automatic letsencrypt wildcard cert renewal with nsupdate
I’m using a wildcard cert from letsencrypt. Currently there is only one way how to verify that you hold the domain you are requesting cert for: creating TXT record in that domain. You can do it by hand when asked by certbot but you don’t want to do this each 90 days. If you are running your own DNS servers with PowerDNS like me there’s an elegant solution: RFC2136. This allows you to update your zones without writing config files and restarting anything.
Continue reading Automatic letsencrypt wildcard cert renewal with nsupdate
My git cheatsheet
Show git log as tree
$ git log --oneline --graph --decorate --all | * 0255f78c (HEAD -> qmtech, my/qmtech) added support for qm_xc6slx16_sdram board | * dae037cf (my/spisingle, spisingle) added spi 1-bit mode, code from litex |/ * 1325aff6 (origin/master, origin/HEAD, master) correctly use result of Record.connect in Converter (#81)
Rebasing
git rebase --onto <where-to> <where-from> <what>
$ git rebase --onto master spisingle qmtech First, rewinding head to replay your work on top of it... Applying: added support for qm_xc6slx16_sdram board $ git log --oneline --graph --decorate --all * 37d2eff0 (HEAD -> qmtech) added support for qm_xc6slx16_sdram board | * 0255f78c (my/qmtech) added support for qm_xc6slx16_sdram board | * dae037cf (my/spisingle, spisingle) added spi 1-bit mode, code from litex |/ * 1325aff6 (origin/master, origin/HEAD, master) correctly use result of Record.connect in Converter (#81)
Push changed branch
$ git push my qmtech -f Counting objects: 7, done. Delta compression using up to 12 threads. Compressing objects: 100% (7/7), done. Writing objects: 100% (7/7), 1.86 KiB | 1.86 MiB/s, done. Total 7 (delta 5), reused 0 (delta 0) remote: Resolving deltas: 100% (5/5), completed with 5 local objects. To https://github.com/danielkucera/misoc.git + 0255f78c...37d2eff0 qmtech -> qmtech (forced update) $ git log --oneline --graph --decorate --all * 37d2eff0 (HEAD -> qmtech, my/qmtech) added support for qm_xc6slx16_sdram board | * dae037cf (my/spisingle, spisingle) added spi 1-bit mode, code from litex |/ * 1325aff6 (origin/master, origin/HEAD, master) correctly use result of Record.connect in Converter (#81)
Set default github username
$ git config --global credential.https://github.com.username danielkucera
Squash commits
git rebase -i <after-this-commit>
replace “pick” on the second and subsequent commits with “squash” or “fixup”
Ignore line endings
git config --global core.autocrlf true
E-mail to SMS
If you are dealing with network monitoring, you might consider using SMSes because they are completely independent. On the other hand, many monitoring systems don’t support HTTP calls (which is the usual way for sending them) but most of them support sending e-mails. Here I want to describe how to configure your server to receive e-mails and transform them to SMSes. Continue reading E-mail to SMS
FL2000 as signal generator
First we need to generate some samples: Continue reading FL2000 as signal generator
FM transmission test with FL2000
My USB 3.0 to VGA adapter arrived a few days ago so I tested the FM transmission example. Continue reading FM transmission test with FL2000