usb_audio: allocate the mic scratch buffer from the port heap - #4
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relic-se merged 1 commit intoAug 13, 2026
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Scott suggested port_malloc() for this in review. It replaces the static int16_t[USB_AUDIO_MAX_SAMPLE_RATE / 1000 * USB_AUDIO_N_CHANNELS] with an allocation sized by enable() for 1 ms at the negotiated rate, so a board that never calls enable() pays nothing for it. On Metro RP2040 .bss drops 188 bytes, the 192 freed less 4 for the pointer, against 32 bytes of added text. enable() can be called more than once, so it releases any chunk sized for a previous rate before taking a new one, and disable() frees as well. Tested 4 s at 48 kHz stereo, 1 kHz left and 3 kHz right, on Metro RP2040, Metro RP2350 and Feather nRF52840. All three write 768044 bytes with full channel separation, matching the static buffer exactly. The nRF52840 keeps both directions on endpoint 8. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Author
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That de-allocation bug is the case this covers. |
Owner
Thanks for validating this as well. Niche use-case, but I could see it happening. |
Owner
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Looking great. Thank you! 🚀 |
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Scott asked for
port_malloc()on the mic scratch buffer in review. I had allthree platforms on the farm today, so I incorporated the suggestion and tested it
rather than leave it hanging.
Same numbers as the static buffer, and the nRF52840 keeps both directions on
endpoint 8. On RP2040
.bssdrops 188 bytes, the 192 freed less 4 for thepointer, against 32 bytes of added text.
Two details beyond the straight swap.
enable()can be called more than once, soit frees any chunk sized for a previous rate first, and
disable()frees too. Itested a boot.py calling
enable(16000)thenenable(48000)and the second onewins.
Yours to take or leave.
🤖 Generated with Claude Code