Now that the Hall effect sensor is working and while the coils are still being tested with the marbles, we started working on our WiFi module. As explained in our project’s presentation, we want our devices to be able to communicate through MQTT with a backend and with other Touch.
The WiFi module :
To do our test we took an ESP32 Wroom-32 Dev kit C. The main purpose of this module will be to connect to the WiFi, receive through MQTT the images that the box will display and then transmit them to the STM32. In some cases, the STM32 will send to the ESP the state of the box and it will have to transfert those data through MQTT.… Read more
We previously tested a Hall effect sensor that, was working, but which gave us a voltage from which we could get the marble’s side. The issue with this is that in the final box, with all the marbles and the coils, we could have had strong pertubations that could alter the data. To avoid this issue we decided to use a sensor that would send the data through a communication protocol that could resist. We chose the TLE493DW2B6A0HTSA1 Infineon Technologies. This sensor sends its data through the I2C protocol so it should resist to our perturbations.
Let’s connect it !… Read more
In the components familly, it was time for the Hall effect sensors to be tested.
We used the SS39ET from HonneyWell. This sensor has 3 pins. One is GND, one is Vcc and the last is the output. The output is a voltage proportional to the magnetic field. We choose for Vcc a value of 3.3V.
First tests, let’s use a voltmeter.
To do the first tests we measure the output voltage with a voltmeter. To power the device we used a DC power supply. We also added an ampermeter to measure the current going to the Hall effect sensor.… Read more
In order to start testing our components (Hall effect sensors and coils), we needed to decide which board and which OS we will use.
Our project will not need to run any complex computation nor doing complex network communications. So almost all processors we checked could be used. We decided that it was better to take a controller little endian based on an ARM processor (because we are more familiar with arm’s instructions). We also wanted it to be low power and not too expensive. With those considerations, we went toward the STM32L475VGT6 because we already had boards at school with it.… Read more
One of the most critical part of the project will be the communication. Whether it is between the Touchs of with the backend we need our device to be able to communicate.
The communication challenge:
The first thing we had to do was to choose the protocol. As we wanted to allow both a communication with a backend and between devices, we chose the MQTT protocol. It has the advantages to be easy to use and to easily allow us to switch from listening to the server to listening an other device.
The first step: the broker:
In MQTT, all devices (may it be a server or an actual connected thing) are clients.… Read more
Touch is an ambitious project which objective is to create a new kind of display device.
Want to know more ? Look here (or click on the menu above)!