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Thursday, 13 June 2019

Homebrew DSP

I will post the rest of the details asap. The base code comes from
I will add some extra bits once happy with them for the IOS7029:2017 age related audio loss compensation and the other filtering options.

But this is almost a no solder project. (Couple 22nF C needed adding to the rotatory controller lines and some simple header wires. The modules tend to include them.

If you shop around and are prepared for the odd long delivery time all mine came to sub £20.

I used:


 A dev board was specified but a bare board will do too. I also tried a discovery board initially.


ILI9341 2.8" TFT module (I used one with touch screen but the original code has no touch components)

AF was TDA2822M Amplifier 2 Channels Stereo 3.5mm AUX Audio Amp Board Module so you can get amplified audio, if want it. These are capable of c5W so more than enough to power larger speakers. Including the rotary pot on the board just £4.99

The rotatory encoder I used a KY-040 Arduino projects module (as it had a pcb and header pins, you could make on veroboard etc.


Giuseppe Callipo IK8YFW said...

Hello, I'm glad that the project is of interest to you, I think to continue with the development, I have identified some interesting modules that can increase the performance of the DSP. I'm working on an additional codec that will replace the mini input output card. This new economic card should help us to increase the s/n ratio already in the acquisition phase. I will use the ADC and DAC of codec card and post to the STM32 module a Digital stream. I hope to get the first results in the coming months after Summer! Now the weather is too warm ! . Vy 73 de Giuseppe Callipo IK8YFW.

M1KTA said...

Thanks Guiseppe, I assumed thi was developed using EmBitz but it doesn't support the F7 or H7 series so I am currently looking at porting over to ST own IDE.

Giuseppe Callipo IK8YFW said...

Yes, you are right, for the new develops I'm testing the Sw4stm32 free ide, It Is based on Eclipse ( a bit slow ), but nice. The EmBitz was a fast and good ide but It is no longer supporter. I think that the porting on other ide will be easy. Good luck, I Will continue with the develop... Bye.

M1KTA said...

I took inspiration from the US guys that used the STM32F4-Doscovery boards and got the STM32F7ZI-Nucleo and STMF746-Discovery Board (one with the attached 4.3" TFT touch display) and playing with the free STM32Cube IDE and GFX display options (under Linux initially). I have a STM32H743 Nucleo Board here too in case need more CPU grunt as it will be dual core. The onboard CODEC though seem to be just 12 bit, not that I think it will matter too much at this stage. Using those boards mean the whole project is almost solder free as the F7 disco board even has the audo in/out on the board.

The larger TFT touch screen looks like an interesting option for control and input selection.

The hearing loss correction seems to be working best if I treated the data as if it were a graphic equalizer algorithm with different frequency segments being amplified or otherwise by a lookup list. Looking to table the ISO 1999:2013 derived values.

Sadly the day job is getting in the way as need more time :-)

M1KTA said...

I haven't bought the newer ISO 7029 data yet 185 CHF for the paper alone seems a tad rich. I understand it was based on the older data anyway (according to hearing aid audio engineer) so not much change. I was using the STM32-AUDIO100A and the 10 band graphic equalizer example in F4's (check out greq_glo.h) as a base. I am sure the X-CUBE-AUDIO firmware has the F7 stuff in it somewhere (greq_?? bits). Reading UM1798 isn't exactly exciting stuff :-)

Giuseppe Callipo IK8YFW said...

Great, fine job!, I think this is the right way, surely working on a discovery board contributes to eliminate every welding need. Meanwhile I am working on the CODEC WM8978, it seems a good codec with great features. I hope to measure a real increase of S / N ratio. Also this codec has internal DSP with filter and equalizer, I will try to use these to wipe the load of STM32 processor, using It for more complex calculus. This Is my first experience with I2S audio protocol and I'm studing a bit. I got this codec from china shop with some test driver for f103 (very raw). I'm writing my own driver for standard library and running on f407 series. I Will take a look to new platform, like xcube, but after completed this experiences.

Ofcourse everything is work in progress, trying to recover some spare time between work and family commitments, I believe that the best time to experiment in peace is the winter season, in the evenings, on those occasions I can work better. ...
Best 73 Giuseppe, Ik8yfw

M1KTA said...

I added an new post and an image of the early layout. 72 Dom M1KTA