Project Swiftlet - Progress Report - Semi-final

Projects / Project Swiftlet  Original post date: 09/20/2015

I don't quite get the point for insisting on making a video presentation. It is very ironic having to make one for something that is designed for visually impaired person. May be I am just not in the video generation or that Hackaday isn't for me.

Here is the non-video version of a progress report summary. Current phrase: progress as of Sept 21

Most of the hardware are implemented. I don’t foresee any big show stopper level surprises for the few hardware that are not tested as they are pretty basic.

Current issues:

• There are a few minor hardware bugs that can be patched with barnacles until a new rev. of PCB is made. There are also some component values changes. Both of these have no impact on getting the rest of the project done.
• Acoustic/mechanical issue with the ultrasonic. I have done all I can as there are no case for better mechanical support/damping of the sensor PCB for the left side. I have to increase the dead zone for close object out to 1ms (~ 17cm/6.7") for now to get range finder to work. I don't think that is a real life problem as the person already have limps making contact at that range.
• Boost mode power supply introduces sub-harmonic noise for Ultrasonic sampling.

• Not a big issue as the tiny speakers aren't good at reproducing audio below 800Hz anyway.

• On the other hand this does raise the noise floor a bit for range finder.

• Also not an issue when using Li-ion battery as it runs off a different power supply.

• Analog comparator in the microcontroller doesn't work reliably for this application.

1. Too "analog" for this application as I have to dynamically change the threshold. It overshoots causing glitches and has long settling time just like an analog comparator would.
2. I switched over to the ADC and its digital comparator and that solved the issue for me.

• I2S & audio play back: Mainly it is a time schedule issue as I only been working on this for a few days.

1. I am on my own.. I have checked Teensy LC I2S not support at the moment in Paul's audio library. No ChibiOS activities for their Kinetis port. There are currently no open source implementation of this.
2. Freescale documentation is very lacking on explanation on their terms which are different than their own app notes for other families.
3. Deciphering the Processor Expert generated code isn't easy and the GUI doesn't have the exact setting that I want.
4. Right now have to do a lot of trial and error with SWD debugger, scope just to get the various clock frequencies divider setting to work.

Work for the next phrase for enhancing capabilities:

Hardware implemented, but no custom driver and libraries implemented yet. Additional capabilities such as voice status/menu hinges on the 6DF sensor and for voice samples storage on the SPI FLASH. Then there is the issue of finding/getting a voice sample for distribution that is license free.

Wishlist:

• Evaluate alternate battery holder (integrated into case???)
• Case design, mechanical mounting
• Improved Ultrasonic sensor board mechanical and mounting to eliminate acoustic issues.
• Evaluate MEMS microphone to replace ultrasonic receiver, speakers to replace ultrasonic transmitter
• Speaker enclosure to enhance performance