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fix(darwin): write without response canSendWriteWithoutResponse #435

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fix(darwin): write without response canSendWriteWithoutResponse #435

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2a7afcc
fix(darwin): write without response use IsReadyToSendWriteWithoutResp…
acouvreur Apr 4, 2026
8efbf23
poll every 15ms instead
acouvreur Apr 4, 2026
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18 changes: 13 additions & 5 deletions gattc_darwin.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ import (
)

var (
errCannotSendWriteWithoutResponse = errors.New("bluetooth: cannot send write without response (buffer full)")
errWriteWithoutResponseTimeout = errors.New("bluetooth: write without response timed out waiting for buffer space")
)

// DiscoverServices starts a service discovery procedure. Pass a list of service
Expand Down Expand Up @@ -236,13 +236,21 @@ func (c DeviceCharacteristic) Write(p []byte) (n int, err error) {
// WriteWithoutResponse replaces the characteristic value with a new value. The
// call will return before all data has been written. A limited number of such
// writes can be in flight at any given time.
// If the client is not ready to send write without response requests at this time (e.g. because the internal buffer is full), an error is returned.
// If the peripheral's buffer is full, this method polls
// CanSendWriteWithoutResponse every 15ms (one BLE connection interval) until
// ready, with a 10-second timeout.
func (c DeviceCharacteristic) WriteWithoutResponse(p []byte) (int, error) {
if !c.service.device.prph.CanSendWriteWithoutResponse() {
return 0, errCannotSendWriteWithoutResponse
dev := c.service.device

deadline := time.Now().Add(10 * time.Second)
for !dev.prph.CanSendWriteWithoutResponse() {
if time.Now().After(deadline) {
return 0, errWriteWithoutResponseTimeout
}
time.Sleep(15 * time.Millisecond)
}

c.service.device.prph.WriteCharacteristic(p, c.characteristic, false)
dev.prph.WriteCharacteristic(p, c.characteristic, false)

return len(p), nil
}
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