back to where i was before the MC upgrade

A project log for Multichannel Audio DSP Field Mixer Recorder

bluetooth app controlled professional portable DSP mixer.balanced audio IO,phantom power,flexible routing,ISO recording. timcode. AVB audio.

ben bilesben biles 10/31/2020 at 10:590 Comments

finally pretty much back where i started before the stm32f7 to H7 upgrade.

I still have an annoying bug in the BT app -> Micro where I need to press a button 3 times before it makes it to the app.. the sliders are probably only sending every 3rd value to. Its obviously a buffer or just the annoying fact I have no EOL character being recognised in the UART between stm32 and HC06 module.

I'm sure there is an obvious fix. I'm using DMA and streaming out tons of meter value data on the same UART. 10 characters go one way and 3 come in for device control. I did try and align the buffer of TX and RX but it didn't help. It could also be the way the App Inventor code sends the characters!


Fixed ! as soon as i finished writing this log , I tried disabling the FIFO buffer on the UART and bingo.

one press on a button and instant reaction in the hardware. The sliders feel more accurate too since there not skipping values.

It's working with an interrupt that happens when 4 character arrive in DMA. my incoming commands are a fixed 4 bytes long. the 1st byte is just a marker to check I am receiving a real command and not garbage.

I don't send back any acknowledge byte yet to the app. 

[end edit]

The individual channel power switching is working. I will need to force a mute on the powered down preamp channels as there is some small noise there. I can do that in the ADC or the DSP , not sure which is better , possibly better to mute the relevant ADC channel so it's quiet when powered back on. Now there is a large thud ( boom ! )

I don't really like the 1.27mm headers , pins can easily snap off and the connections are not as solid as 2.54mm. looking forward to the day I can just solder those preamp cards onto the backplane !  There is no way I would have got 8 preamp channels in such a small box with the larger headers so no choice ! I do wonder if I would have been better off using flat flex ribbon cables like in a mobile phone.

I think the next job after fixing the BT uart will be ltc timecode IO which will come through the TI Codec on SAI3. I'm really looking forward to that from a C code perspective. Then right after that I have to wake up the RTC TXCO and figure out how to jam sync incoming timecode to it :)

Way off into the future but hopefully before next year I will get the Xmos chip awake and get AES3 IO in and out of the DSP ! Hopefully I can setup TDM8 on the XMOS to sync up the the DSP as a slave without to much trouble. 

AVB seams like pipe dreams now , but the gigabit ethernet PHY IC is there waiting and connected to XMOS.

I doubt USB C sound card mode will work at the same time as AES3 and AVB but who knows ! that will be decided by XMOS computational power and my coding ability in the XMOS IDE i think.