Episode 2 : more changes

Last Friday, we discussed with Alexis Polti and Samuel Tardieu of our current view of the project. This was really interesting.

First : our assumption that Ethernet would be great was false. Even in a local Ethernet segment we can’t assume that the jitter would be nearly inexistant if there is other people using the segment. No more lwIP then 🙂

As using Ethernet was mainly used to synchronize the beeps, they proposed a solution : using the emitters timer and just synchronize their clock using RF.


ZigBee sync architecture


So I wrote a prototype of code for the TP boards : a master would emit a synchro pulse via ZigBee every 4s, and two slaves will reset their timer when this message will be received. The timer interrupt would then be used to generate a pulse on a GPIO.

Using the LED as output, slaves clocks seemed to be well synchronized, but I need to analyze this using a logic analyzer to figure out if the slaves clocks are really synchronized enough for us.

Then, Alexis Polti told us that it was useless to use a class A amplifier with a pure sinus : making a square wave using the PWM output with a class D amplifier will result in a much higher efficiency. The piezzo tweeter will then filter out the square form to make it a square wave. No more DAC used.

In the week-end Issam and Jean-Baptiste made huge progress on the simulation side, but I’ll let them explain their work 🙂

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