Architecturing

Last Wednesday, we finished discussing about architecture. We made some major changes.

First, we discovered that we couldn’t use the TLC59582. We made some assumptions about the way ES-PWM works that aren’t specified in the Datasheet. We thought we could control the PWM width over one segment using the 8 MSB, and we could send a VSYNC signal in the middle of the PWM period. This would have resulted in an 8bit PWM, which is ideal. Without these assumptions, we only have a 12bit PWM which period is too long compared to the display time of a single point.

After checking a lot of LED drivers and PWM generators, I couldn’t find anything suitable except for the TLC5957. Most drivers are either using 12-bits PWM, or using an 8-bits PWM but with really insufficient data rates. The TLC5957 has the advantage of being configurable from 9 to 14 bits (resulting in small enough PWM period when used with 9 or 10 bits), and with a really high data rate.

We also had to think about how to configure the Wifi. After thinking about a bunch of scenarii, we went with the simplest solution since we are running late. We will use a button on the mobile part used to turn the Wifi module into AP mode. It will also start a web server that can be used to configure the Wifi AP to connect to.

Finally, and again for sake of simplicity, we decided that the fixed and mobile parts will not communicate since it’s not strictly necessary. The fixed part will use a switch to start and stop the motor, and a photosensor to get feedback on the motor’s speed. Since the motor is controlled with 5V logics, and we do not longer need Wifi or Bluetooth, we will use an Arduino Micro instead of the ESP32. It can be powered using 12V, provides a regulated 5V/1A pin, and PWM capable 5V GPIOs.

Schematics

I’m beginning to work on the schematics. For know, I designed one LED panel including its driver and column multiplexing.