embassy-rp/cyw43-pio: fix input_sync_bypass for pins >= 32 (GPIOBASE offset)#6391
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cedrivard wants to merge 4 commits into
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embassy-rp/cyw43-pio: fix input_sync_bypass for pins >= 32 (GPIOBASE offset)#6391cedrivard wants to merge 4 commits into
cedrivard wants to merge 4 commits into
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added 2 commits
June 20, 2026 12:14
set_input_sync_bypass built the bitmask with the absolute pin number, but input_sync_bypass is indexed relative to the PIO's GPIOBASE. On RP235xB with GPIOBASE=16, a pin >= 32 (e.g. GPIO 38) shifted by the full pin number, which panics in debug and wraps to the wrong bit in release. Subtract the GPIOBASE offset (read from the register) before shifting.
input_sync_bypass is indexed relative to GPIOBASE, which is only established by StateMachine::set_config. Calling it at pin creation (before set_config) read a stale GPIOBASE of 0, so the offset was wrong for the CYW43 data pin on boards that wire it to a pin >= 32 (RP235xB). Move the call after set_config.
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Problem
Pio::Pin::set_input_sync_bypassbuilds the bitmask from the absolute pinnumber (
1 << self.pin()), butinput_sync_bypassis indexed relative to thePIO's
GPIOBASE(0 or 16 on RP235x). On RP235xB withGPIOBASE = 16, a pinThis breaks
cyw43-pioon boards that wire the CYW43 data line to a high pin.On the SparkFun IoT RedBoard RP2350 (RP2350B; CYW43 on GPIO 36/37/38),
cyw43::new()hangs: without a working sync bypass the PIO samples stale dataand the link never comes up.
Fix
1.
embassy-rp— offset the mask by GPIOBASE. Shift bypin - offset,reading the offset (0/16) from the
GPIOBASEregister instead of assuming afixed value (resolving the 16..31 ambiguity from #5116).
2.
cyw43-pio— call it afterset_config.GPIOBASEis only written byStateMachine::set_config, but the call was at pin creation, beforeset_config, so the register read returned a stale 0. Moving it aftersm.set_config(&cfg)makes the offset correct.Testing
Verified on hardware (SparkFun IoT RedBoard RP2350, RP2350B):
cyw43::new()succeeds and WiFi associates, replacing a manual
INPUT_SYNC_BYPASSwrite I'dbeen carrying downstream.
Supersedes #5116 (same root cause); credit to @diogo464 for the original report
and the ordering insight, and @Dirbaio for the GPIOBASE review note.