Makahiya – audio codec, Flexinol and LEDs

Hi everybody,

This week is fully dedicated to the ROSE project so I had time to work on several aspects of it.

The audio codec was the most time-consuming one because I spent hours trying to understand why I wasn’t able to play music on the board. As Tanguy said, I managed to have the I2S work last Sunday afternoon but it was no the end of my problems. Because yes I was able to talk to the codec but we didn’t understand each other. I explored several ways in order to understand what I was doing wrong. I expected that the problem was related to sampling frequency because that part isn’t clear to me: I don’t clearly understand which signal corresponds to what value. But it wasn’t that. Samuel found a code he used for the 2014 communication challenge and that was able to communicate with the codec. I adapted this code to the new version of ChibiOS and it worked !! I still have to change a bit this code in order to use the I2S driver that was added in ChibiOS in the meanwhile  (it uses DMA, so it’s better than doing it by hand on the microprocessor). And I also found a software codec made for running on embedded systems and that is able to decode ogg files. With this 2 infos, we validate the choice of the CS4344 as our audio codec (as Alexis suggested us to do).

I also made some tests with the Flexinol and our banana tree, in order to see if I was able to move the leaves. And the result was very disappointing… So I tested with a simple motor and a wire and it worked very well. With this solution, the result is really convincing (according to me at least). When I showed it to Alexis, he approved my choice: we’ll abandon the Flexinol and use servomotors instead.

Finally, I tested the most powerful LED we have (the one which was abandonned few weeks ago) with the optical fiber, to see if the light was visible even during the day (because with the other LEDs, it’s only visible by night). And it is, so we decided to add one powerful LED to our product in order to make some flash visible even during the day (to signal that you’ve just received a message for instance). We take only one of them, because they need a very high current (up to 2.8A each).

During the second part of this week, we want/have to finish the schematic and the placement/routing of the PCB. Tanguy will probably do most of the job on this part. So I will try to improve the communication with the CS4344 and test the software codec.

Makahiya – flexinol & schematic

Hi everybody,

During this first part of the week, I implemented Tanguy’s suggestion in the touch detection algorithm. For now, it works as well as the previous solution and is able to detect all the touches in the samples I’ve in the automatic tests. I didn’t have time to add new tests so I can’t say that tests proved that it’s a better solution for the moment (but I think it is).

On Monday, I did some tests in order to choose which coaxial cable to use because we had 2 different diameters. The bigger one, the one I’d used so far, appeared to be the best, by far: peaks when approching the hand are much more visible. So we’ll keep this one. And we talked with Alexis about the heat sink that we need for the LEDs. As finding information on this topic is quite difficult and as it’s not necessary to know it for the PCB, we decided to take care of this part later, after having finished the PCB.

On Tuesday, we received the Flexinol wires ordered by Alexis. I did several tests with them. To “program” a new shape, a candle seems to be enough. If possible, I’ll test with something a bit more powerful like a torch to see if there is a difference. These tests showed me that it’s harder to use than expected, especially programming a new shape. With the smallest ones (the one we asked Alexis to order), I didn’t manage to program a shape. However, Alexis had ordered bigger ones (thank you Alexis for this), that work better. I was able to move up and down a pair of scissors with them. But they need much more current than the others: 1.3A each.. So we have again a problem with the power supply… We have to think about it in the next days.

By the end of the week, we’ll do some tests with the audio codec embedded in our development board Olimex-P407 to see if it meets our requirements. And I’ll do more tests with the Flexinol.