Skip to content

machine/rp2: stop SPI1 transmit from restarting SPI0 DMA #6010

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
deadprogram merged 1 commit into from
Oct 24, 2026
Merged

machine/rp2: stop SPI1 transmit from restarting SPI0 DMA #6010

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 6 additions & 3 deletions src/machine/machine_rp2_spi.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -274,28 +274,31 @@ func (spi *SPI) tx(tx []byte) error {
}

// Pick the DMA channel reserved for this SPI peripheral.
var ch *dmaChannel
var channel uint32
var dreq uint32
if spi.Bus == rp.SPI0 {
ch = &dmaChannels[spi0DMAChannel]
channel = spi0DMAChannel
dreq = rp.DREQ_SPI0_TX
} else { // SPI1
ch = &dmaChannels[spi1DMAChannel]
channel = spi1DMAChannel
dreq = rp.DREQ_SPI1_TX
}
ch := &dmaChannels[channel]

// Configure the DMA peripheral as follows:
// - set read address, write address, and number of transfer units (bytes)
// - increment read address (in memory), don't increment write address (SSPDR)
// - set data size to single bytes
// - set the DREQ so that the DMA will fill the SPI FIFO as needed
// - chain to itself, which disables chaining
// - start the transfer
ch.READ_ADDR.Set(uint32(unsafeNoEscape(unsafe.Pointer(unsafe.SliceData(tx)))))
ch.WRITE_ADDR.Set(uint32(uintptr(unsafe.Pointer(&spi.Bus.SSPDR))))
ch.TRANS_COUNT.Set(uint32(len(tx)))
ch.CTRL_TRIG.Set(rp.DMA_CH0_CTRL_TRIG_INCR_READ |
rp.DMA_CH0_CTRL_TRIG_DATA_SIZE_SIZE_BYTE<<rp.DMA_CH0_CTRL_TRIG_DATA_SIZE_Pos |
dreq<<rp.DMA_CH0_CTRL_TRIG_TREQ_SEL_Pos |
channel<<rp.DMA_CH0_CTRL_TRIG_CHAIN_TO_Pos |
rp.DMA_CH0_CTRL_TRIG_EN)

// Wait until the transfer is complete.
Expand Down
Loading