I use Flask and Flask-SQLAlchemy for a while now. Doing so i spent a lot of time in searching for the solutions for different problems. See this as my notebook of helpfull snippets. I will update this post from time to time because i don’t want to create a new blog post for each line of helpfull code.

I work on a project that has a form including a map, so a logged in user can enter his data and drawing features on the map and save it afterwards. The user gets a page that shows the map with the features on it. I will show how to save and restore the drawn data as geoJSON and how to save circles because that type of feature is not supported by geoJSON.

Because i’ve got a lot of emails during the last year with several questions about my MDB projects, i try to answer them here.

Making web uploads less painfull 🔗For one of my current Flask projects i want to have a nice looking and easy to use file upload form. That means no input type="file" form field where i have to select each file and the upload it on at a time. I came across this nice tutorial for a HTML5/jquery file uploader, but the backend is written in PHP. So I decided to try to get this working with Flask and it was easier as I supposed :-)

I finally activated the Disqus comment system for my blog. I wanted to do this for a while now but was to lazy to do it :-)

I do a few webprojects with Flask and I love it! While creating a template i searched for a way to call functions from within the template, and found out that i can use a @app.context_processor decorator.

The problem 🔗I have built a PCB drill that works nice most of the time, but sometimes it occurs that the stepper motor don’t perform a full turn. This is caused by the friction of the eccentric tappet. I’ve simply made it out of a piece of steel rod, with a hole outside of its center. That tappet pushes a brass screw upwards. I thought that this will work fine, but it does not (sometimes).

I just want to announce that i’ve published my MDB cashless device code for the MateDealer project on github. It would be nice to get some feedback! Here is the github repo

Last Tuesday I’ve nearly finished the complete code for the MateDealer project. After I’ve successfully vended a Club Mate (that is the drink the MateDealer got it’s name from) I loged the MDB communication with my logic analyzer. I have taken a few screenshots of the logic trace and now i will try to explain the complete procedure.

Today I want to show you how I connected our vending machine to the Arduino Mega 2560. With a piece of stripboard i made a board that can be stacked on an Arduino like a real shield. As you can see the board is really simple. It contain just 2 otocouplers to insulate the Arduino from the Vending machine controller, 2 resistors for the leds of each optocoupler and one as a pullup resistor. The values of the resistors might be not perfect, but for me those values worked fine all the time. The optocpuplers are PC814 types. The can be exchanged with other types if you dont have theese available. The board uses the UART1 for the communication. So I can use UART0 which is also used to program the Arduino to communicate with a PC. That has the nice effect that i can connect the Arduino with USB to the PC.