Become the sender !

As I wrote in my previous posts, the ESP, the STM and the server were working together to receive images or animations depending of what the user wants. Now it’s time for the STM to become the sender.

The objective:

We want the devices to be able to received images from the server but we also want to establish a connection between Touchs to send images from one to the other. On top of that at the end we want to have a communication between both devices in both ways. But as you may know chi va piano va sano. So first things firts, we implemented the emitting part for the first device.… Read more

PCB: Last step (until we found an error)

On Wednesday, I finished the PCB. I used one trick that found Alexis on our test PCB. We have two VCC, one for the coils and the other for all the other components. So, I create a two-parts plan. The VCC is in green and the VCC_COIL is in yellow.

I also have to route all the components. I found a way to make the routing easier, by enforcing a simple rule. When the route is horizontal, it must be on the top face, and when it is vertical, it must be on the bottom face. I also have to change the pins of the multiplexers in order to route them easily.… Read more

PCB: step 2

On Monday, I routed the 4×4 PCB I placed on Friday. I choose to put one multiplexer at the top of this cell and another one at the right. So the SDA lines (which come from the STM32, not from the multiplexer) will come from the left and the bottom. I also changed the scheme by removing a pull-up I put between the main multiplexer and the other multiplexers.

I try to use some shortcuts I found such as one that swaps the pins, but after reading the manual, I found that without a change in the part editor, I cannot use it, so I finally change the pins in the scheme

Now, I will copy 16 times this cell and continue routing with the other components

PCB: step by step

On Friday, I continued to place components. I spent some time to put the 4×4 coils precisely (in the same way as for the test PCB. I found some keyboard shortcuts that help me to do this quickly, but of course, I found the best shortcuts on Monday, when most of the work was done. I take a look at Alexis’ work he made on our test PCB and found some toolbars that will be very useful for me.

Now, I will try to place the multiplexer and to route it. Then I will copy this 4×4 grid sixteen times to finish the PCB until placing and routing the unique components.

Ready for a test of PCB?

On Thursday, I went to Telecom for the first time of the week. I took advantage of this journey to print the prototype of our box for the test PCB. But I lack plastic plank for the middle part (in green in other photos), so we need to wait for a week to have it. However, we will have it on time because we won’t have the PCB before.

In the afternoon, I began the final PCB. We found before a component for charging the battery on a USB cable (the LTC4088), that I put in the schemes.

After some hours on it, I finally find how to import a DXF file of our PCB.… Read more

4×4 is to easy, let’s have a look at 16×16

On Monday, I began to have a look at a 16×16 device scheme. For this, I took the 4×4 scheme, I copied it 16 times, and I added two multiplexers. One that will multiplex the SCL signal to the multiplex that controls the Hall effect sensor, and one other that will multiplex the multiplexer that controls the H-bridge drivers. Then, I had some questions.

Should I keep a pull-up or a pull-down between two multiplexers or not? My answers for this moment is to keep a pull-up in order to avoid a clock signal on SCL if there is some latch between the two multiplexers.… Read more

PCB and Scheme

Finishing the test_PCB

Last week, I made a lot of routing to finish our first test PCB. We choose with Alexis to make a PCB that would work with an alimentation because it was easier, so I had a lot of more things to do, but after some work, I finished this part.

Scheme of the box

In order to understand better the design of our box, I made a scheme of the organization if you want to try to do a Touch at home with this design.

This was not clear in my previous post, but this design allows the marbles to flip when the box is put horizontally and vertically.… Read more

Let’s push it !

So far, the ESP32 was able to receive images from the server through MQTT and transmit them to the STM32. It also could transmit animations but only if the animation was directly hardcoded. So what we wanted to do was to be able to transmit animations through MQTT just like images and also to find a way to chose if we want to receive an animation or an image.

First things first : the server side

The first step we did to go in this direction was to find a way to transmit animations.
We chose that, at least for now, the server will publish periodically on two topics.… Read more

Catchin’ up with the posts

To hell those marbles

Last friday I mainly worked on getting the new marbles (the ones that hadn’t undergone any heating process) to the desired magnetic field values. Remember, on this post I had already manage to have the marbles we already heated at the desired value. It needed a heating time around 5 min, so I instinctively thought that for marbles that had undergone no heating, it would need a longer time. I was wrong. And not slightly wrong, but more like completely wrong.

So I started heating at 300°C for 6 mins, it was too much and the magnetic field almost completely disappeared (barely noticeable).… Read more