Enable full-duplex I2S for spi_v2 devices using I2SEXT peripherals#5773
Draft
bifurcation wants to merge 3 commits intoembassy-rs:mainfrom
Draft
Enable full-duplex I2S for spi_v2 devices using I2SEXT peripherals#5773bifurcation wants to merge 3 commits intoembassy-rs:mainfrom
bifurcation wants to merge 3 commits intoembassy-rs:mainfrom
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The STM32F4 SPI2/SPI3 peripherals have associated I2SEXT peripherals (I2S2EXT/I2S3EXT) that enable true full-duplex I2S. These are not in stm32-metapac, so we define custom traits for the SPI-to-I2SEXT register mapping, DMA request numbers, and AF pin assignments. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- Add I2SEXT peripheral traits (I2sExtRegs, RxDmaExt, SdExtPin) for STM32F405 SPI2/SPI3 - Add new_full_duplex constructor for spi_v2 using I2SEXT - Add regs_tx/regs_rx helpers and read_write method - Update start/stop to handle I2SEXT peripheral enable/disable - Configure I2SEXT in new_inner with opposite direction and slave mode - RX DMA reads from I2SEXT register block when present - Rename existing spi_v3 full_duplex to new_full_duplex_native - Enable I2S (set_i2se) in start() for spi_v1/v2/v3 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The I2SEXT-based full-duplex method works on both spi_v1 (STM32F405 in embassy 0.4) and spi_v2 (embassy 0.5). Widen the cfg gate so the constructor is available on both. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Author
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This PR is also based on an older commit of |
Contributor
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@bifurcation hang on a minute, I'm going to rework the traits a bit... |
Author
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@xoviat No rush! My fork is working for me right now, so we can do thus on whatever schedule you like. I just refreshed the PR with my latest state since I saw your ping. |
Merged
Contributor
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@bifurcation I just merged #5774, which should have the traits that you need to complete this. |
This was referenced Apr 2, 2026
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Fixes #4698
There are two classes of changes in this PR: Ones that will be permanent, and ones that are temporary until stm32-metapac gets updated to reflect information about I2SEXT peripherals.
Changes of the latter type are reflected in a few traits at the top of the file. I have mimicked traits such as WsPin and RxDma, which is nice because it preserves a bunch of the design patterns below. It seems like metapac just needs to add these traits and implement them as appropriate for a device, but I don't grok metapac well enough to make this change right now. The I2sRegs trait should probably be absorbed into spi::Instance.
The permanent changes are of the following character:
Marking this as draft because of the above-mentioned issues, and because of the unresolved dependency on metapac changes. I have tested this on a real device using
stm32f405rgusing SPI to talk to anWM8960and it works reliably, but I have not tested not more generally.Replaces #4746