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Fix SH1106 issue when there are other i2c devices on the line and tra… #431

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Merged
marcelstoer merged 1 commit into from
May 28, 2026
Merged

Fix SH1106 issue when there are other i2c devices on the line and tra… #431

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97 changes: 60 additions & 37 deletions src/SH1106Wire.h
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ class SH1106Wire : public OLEDDisplay {

void display(void) {
initI2cIfNeccesary();
#ifdef OLEDDISPLAY_DOUBLE_BUFFER
#if defined(OLEDDISPLAY_DOUBLE_BUFFER)
uint8_t minBoundY = UINT8_MAX;
uint8_t maxBoundY = 0;

Expand All @@ -111,8 +111,8 @@ class SH1106Wire : public OLEDDisplay {

uint8_t x, y;

// Calculate the Y bounding box of changes
// and copy buffer[pos] to buffer_back[pos];
// Calculate the bounding box of changes. Do not update buffer_back yet:
// if an I2C transfer fails, the same dirty region must be retried.
for (y = 0; y < (displayHeight / 8); y++) {
for (x = 0; x < displayWidth; x++) {
uint16_t pos = x + y * displayWidth;
Expand All @@ -122,7 +122,6 @@ class SH1106Wire : public OLEDDisplay {
minBoundX = _min(minBoundX, x);
maxBoundX = _max(maxBoundX, x);
}
buffer_back[pos] = buffer[pos];
}
yield();
}
Expand All @@ -136,47 +135,52 @@ class SH1106Wire : public OLEDDisplay {
uint8_t minBoundXp2H = (minBoundX + 2) & 0x0F;
uint8_t minBoundXp2L = 0x10 | ((minBoundX + 2) >> 4 );

uint8_t k = 0;
bool txOk = true;
for (y = minBoundY; y <= maxBoundY; y++) {
sendCommand(0xB0 + y);
sendCommand(minBoundXp2H);
sendCommand(minBoundXp2L);
for (x = minBoundX; x <= maxBoundX; x++) {
if (k == 0) {
_wire->beginTransmission(_address);
_wire->write(0x40);
}
_wire->write(buffer[x + y * displayWidth]);
k++;
if (k == I2C_OLED_TRANSFER_BYTE) {
_wire->endTransmission();
k = 0;
}
// Both sendCommandChecked calls always execute (left operands of &&), ensuring both address
// commands are sent to the display. pageOk becomes false if either command fails.
bool pageOk = sendCommandChecked(0xB0 + y);
pageOk = sendCommandChecked(minBoundXp2H) && pageOk;
pageOk = sendCommandChecked(minBoundXp2L) && pageOk;
if (!pageOk) {
txOk = false;
yield();
continue;
}
if (k != 0) {
_wire->endTransmission();
k = 0;
for (x = minBoundX; x <= maxBoundX;) {
uint8_t chunkSize = _min((uint16_t)I2C_OLED_TRANSFER_BYTE, (uint16_t)(maxBoundX - x + 1));
if (!sendDataChunk(&buffer[x + y * displayWidth], chunkSize)) {
txOk = false;
break;
}
x += chunkSize;
}
yield();
}

if (k != 0) {
_wire->endTransmission();
if (txOk) {
uint16_t changedWidth = maxBoundX - minBoundX + 1;
for (y = minBoundY; y <= maxBoundY; y++) {
uint16_t pos = minBoundX + y * displayWidth;
memcpy(&buffer_back[pos], &buffer[pos], changedWidth);
}
}
#else
uint8_t * p = &buffer[0];
for (uint8_t y=0; y<8; y++) {
sendCommand(0xB0+y);
sendCommand(0x02);
sendCommand(0x10);
for( uint8_t x=0; x<(128/I2C_OLED_TRANSFER_BYTE); x++) {
_wire->beginTransmission(_address);
_wire->write(0x40);
for (uint8_t k = 0; k < I2C_OLED_TRANSFER_BYTE; k++) {
_wire->write(*p++);
bool txOk = true;
for (uint8_t y=0; y<(displayHeight / 8); y++) {
bool pageOk = sendCommandChecked(0xB0 + y);
pageOk = sendCommandChecked(0x02) && pageOk;
pageOk = sendCommandChecked(0x10) && pageOk;
if (!pageOk) txOk = false;
for(uint16_t x=0; x<(displayWidth / I2C_OLED_TRANSFER_BYTE); x++) {
if (pageOk && !sendDataChunk(p, I2C_OLED_TRANSFER_BYTE)) {
txOk = false;
pageOk = false;
}
_wire->endTransmission();
p += I2C_OLED_TRANSFER_BYTE;
}
yield();
}
#endif
}
Expand All @@ -190,10 +194,29 @@ class SH1106Wire : public OLEDDisplay {
return 0;
}
inline void sendCommand(uint8_t command) __attribute__((always_inline)){
sendCommandChecked(command);
}

bool sendCommandChecked(uint8_t command) {
for (uint8_t attempt = 0; attempt < 2; attempt++) {
_wire->beginTransmission(_address);
_wire->write(0x80);
_wire->write(command);
if (_wire->endTransmission() == 0) return true;
yield();
}
return false;
}

// Note: sendDataChunk does not retry on I2C failure (unlike sendCommandChecked which retries twice).
// Rationale: Command retries are low-cost/high-value (reset display address state); data retries would
// require recalculating page/column address, making them impractical. The caller (display()) tracks
// txOk to skip buffer_back sync if any chunk fails, allowing the dirty region to be retried on the next call.
bool sendDataChunk(const uint8_t *data, uint8_t length) {
_wire->beginTransmission(_address);
_wire->write(0x80);
_wire->write(command);
_wire->endTransmission();
_wire->write(0x40);
_wire->write(data, length);
return _wire->endTransmission() == 0;
}

void initI2cIfNeccesary() {
Expand Down
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