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feat: optional hooks around long e-ink BUSY waits #21

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feat: optional hooks around long e-ink BUSY waits #21

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16 changes: 16 additions & 0 deletions libs/display/EInkDisplay/include/EInkDisplay.h
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,17 @@ class EInkDisplay {
// Power management
void deepSleep();

// Optional hooks fired around long BUSY waits. A refresh takes ~0.3-2 s during
// which the CPU only polls the BUSY pin; these let host firmware save power in
// that window (e.g. reduce the CPU clock) without the SDK knowing the policy.
// The begin hook fires once a wait exceeds BUSY_WAIT_HOOK_THRESHOLD_MS (so
// short command waits never pay for it); the matching end hook fires when the
// wait completes. Plain function pointers; both default to disabled.
void setBusyWaitHooks(void (*beginHook)(), void (*endHook)()) {
_busyWaitBeginHook = beginHook;
_busyWaitEndHook = endHook;
}

// Access to frame buffer
uint8_t* getFrameBuffer() const {
return frameBuffer;
Expand All @@ -133,6 +144,11 @@ class EInkDisplay {
// Internal geometry setter used by setDisplayX3().
void setDisplayDimensions(uint16_t width, uint16_t height);

// Busy-wait hooks (see setBusyWaitHooks)
static constexpr unsigned long BUSY_WAIT_HOOK_THRESHOLD_MS = 20;
void (*_busyWaitBeginHook)() = nullptr;
void (*_busyWaitEndHook)() = nullptr;

// Pin configuration
int8_t _sclk, _mosi, _cs, _dc, _rst, _busy;

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23 changes: 19 additions & 4 deletions libs/display/EInkDisplay/src/EInkDisplay.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -579,10 +579,19 @@ void EInkDisplay::waitForRefresh(const char *comment) {

void EInkDisplay::pollBusy(const char *comment, const char *completeWord) {
unsigned long start = millis();
// The begin hook fires lazily, only once the wait has proven long (see
// setBusyWaitHooks); hookFired guarantees the end hook is balanced with it.
bool hookFired = false;
bool x3SawLow = false;
if (!_x3Mode) {
// X4: BUSY held HIGH while busy, drops LOW when done.
while (digitalRead(_busy) == HIGH) {
delay(1);
if (!hookFired && _busyWaitBeginHook != nullptr &&
millis() - start > BUSY_WAIT_HOOK_THRESHOLD_MS) {
hookFired = true;
_busyWaitBeginHook();
}
if (millis() - start > 30000)
break;
}
Expand All @@ -595,23 +604,29 @@ void EInkDisplay::pollBusy(const char *comment, const char *completeWord) {
// LOW -> HIGH edge. If we never observe the LOW phase the operation
// either completed faster than we could see or was a no-op, and we
// skip the completion log line.
bool sawLow = false;
while (digitalRead(_busy) == HIGH) {
delay(1);
if (millis() - start > 1000)
break;
}
if (digitalRead(_busy) == LOW) {
sawLow = true;
x3SawLow = true;
while (digitalRead(_busy) == LOW) {
delay(1);
if (!hookFired && _busyWaitBeginHook != nullptr &&
millis() - start > BUSY_WAIT_HOOK_THRESHOLD_MS) {
hookFired = true;
_busyWaitBeginHook();
}
if (millis() - start > 30000)
break;
}
}
if (!sawLow)
return;
}
if (hookFired && _busyWaitEndHook != nullptr)
_busyWaitEndHook();
if (_x3Mode && !x3SawLow)
return;
if (comment && Serial)
Serial.printf("[%lu] %s: %s (%lu ms)\n", millis(), completeWord, comment,
millis() - start);
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