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Add per-byte timeout budget for rp2 I2C #5189

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Add per-byte timeout budget for rp2 I2C #5189

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727781c
Add per-byte timeout budget for rp2 I2C
sparques Jan 26, 2026
f7472d5
run goimports
sparques Jan 26, 2026
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10 changes: 8 additions & 2 deletions src/machine/machine_rp2_i2c.go
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Original file line number Diff line number Diff line change
Expand Up @@ -280,8 +280,6 @@ func (i2c *I2C) deinit() (resetVal uint32) {

// tx performs blocking write followed by read to I2C bus.
func (i2c *I2C) tx(addr uint8, tx, rx []byte) (err error) {
const timeout_us = 4_000
deadline := ticks() + timeout_us
if addr >= 0x80 || isReservedI2CAddr(addr) {
return errInvalidTgtAddr
}
Expand All @@ -292,6 +290,14 @@ func (i2c *I2C) tx(addr uint8, tx, rx []byte) (err error) {
return nil
}

// Base 4ms for small register pokes.
// Add per-byte budget. 100us/byte is conservative at 400kHz and still ok at 100kHz for modest sizes.
timeout_us := uint64(4_000) + uint64(txlen+rxlen)*100
// Cap so it doesn't go insane:
timeout_us = min(timeout_us, 500_000)

deadline := ticks() + timeout_us

err = i2c.disable()
if err != nil {
return err
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