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fix qmax entries so fcc is limited to 2000mah and not 3000mah

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pelgraine
2026-03-01 23:49:02 +11:00
parent 4bb721e060
commit 1ecda1a8f5
1 changed files with 138 additions and 45 deletions
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183
variants/lilygo_tdeck_pro/TDeckBoard.cpp
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@@ -180,7 +180,7 @@ static bool bq27220_writeControl(uint16_t subcmd) {
#endif
// ---- BQ27220 Design Capacity configuration ----
// The BQ27220 ships with a 3000 mAh default. The T-Deck Pro uses a 1400 mAh
// The BQ27220 ships with a 3000 mAh default. The T-Deck Pro uses a 2000 mAh
// cell. This function checks on boot and writes the correct value via the
// MAC Data Memory interface if needed. The value persists in battery-backed
// RAM, so this typically only writes once (or after a full battery disconnect).
@@ -197,29 +197,23 @@ bool TDeckBoard::configureFuelGauge(uint16_t designCapacity_mAh) {
if (currentDC == designCapacity_mAh) {
// Design Capacity correct, but check if Full Charge Capacity is sane.
// After a Design Capacity change, FCC may still hold the old factory
// value (e.g. 3000 mAh) until a RESET forces reinitialization.
uint16_t fcc = bq27220_read16(BQ27220_REG_FULL_CAP);
Serial.printf("BQ27220: Design Capacity already correct, FCC=%d mAh\n", fcc);
if (fcc >= designCapacity_mAh * 3 / 2) {
// FCC is >=150% of design — stale from factory defaults.
// The gauge derives FCC from Design Energy (not just Design Capacity).
// Design Energy = capacity × nominal voltage (3.7V for LiPo).
// If Design Energy still reflects 3000 mAh, FCC stays at 3000.
// Fix: enter CFG_UPDATE and write correct Design Energy.
Serial.printf("BQ27220: FCC %d >> DC %d, updating Design Energy\n",
fcc, designCapacity_mAh);
// FCC is >=150% of design — stale from factory defaults (typically 3000 mAh).
uint16_t designEnergy = (uint16_t)((uint32_t)designCapacity_mAh * 37 / 10);
Serial.printf("BQ27220: Target Design Energy = %d mWh\n", designEnergy);
Serial.printf("BQ27220: FCC %d >> DC %d, checking Design Energy (target %d mWh)\n",
fcc, designCapacity_mAh, designEnergy);
// Unseal
// Unseal to read data memory and issue RESET
bq27220_writeControl(0x0414); delay(2);
bq27220_writeControl(0x3672); delay(2);
// Full Access
bq27220_writeControl(0xFFFF); delay(2);
bq27220_writeControl(0xFFFF); delay(2);
// Enter CFG_UPDATE
// Read current Design Energy from data memory to check if it needs writing
// Enter CFG_UPDATE to access data memory
bq27220_writeControl(0x0090);
bool ready = false;
for (int i = 0; i < 50; i++) {
@@ -228,52 +222,135 @@ bool TDeckBoard::configureFuelGauge(uint16_t designCapacity_mAh) {
if (opSt & 0x0400) { ready = true; break; }
}
if (ready) {
// Design Energy is at data memory address 0x92A1 (2 bytes after DC at 0x929F)
// Read old values for checksum calculation
// Read Design Energy at data memory address 0x92A1
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x3E); Wire.write(0xA1); Wire.write(0x92);
Wire.endTransmission();
delay(10);
uint8_t oldMSB = bq27220_read8(0x40);
uint8_t oldLSB = bq27220_read8(0x41);
uint8_t oldChk = bq27220_read8(0x60);
uint8_t dLen = bq27220_read8(0x61);
uint16_t currentDE = (oldMSB << 8) | oldLSB;
uint8_t newMSB = (designEnergy >> 8) & 0xFF;
uint8_t newLSB = designEnergy & 0xFF;
uint8_t temp = (255 - oldChk - oldMSB - oldLSB);
uint8_t newChk = 255 - ((temp + newMSB + newLSB) & 0xFF);
if (currentDE != designEnergy) {
// Design Energy actually needs updating — write it
uint8_t oldChk = bq27220_read8(0x60);
uint8_t dLen = bq27220_read8(0x61);
uint8_t newMSB = (designEnergy >> 8) & 0xFF;
uint8_t newLSB = designEnergy & 0xFF;
uint8_t temp = (255 - oldChk - oldMSB - oldLSB);
uint8_t newChk = 255 - ((temp + newMSB + newLSB) & 0xFF);
Serial.printf("BQ27220: DE old=0x%02X%02X new=0x%02X%02X chk=0x%02X\n",
oldMSB, oldLSB, newMSB, newLSB, newChk);
Serial.printf("BQ27220: DE old=%d new=%d mWh, writing\n", currentDE, designEnergy);
// Write new Design Energy
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x3E); Wire.write(0xA1); Wire.write(0x92);
Wire.write(newMSB); Wire.write(newLSB);
Wire.endTransmission();
delay(5);
// Write checksum
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x60); Wire.write(newChk); Wire.write(dLen);
Wire.endTransmission();
delay(10);
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x3E); Wire.write(0xA1); Wire.write(0x92);
Wire.write(newMSB); Wire.write(newLSB);
Wire.endTransmission();
delay(5);
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x60); Wire.write(newChk); Wire.write(dLen);
Wire.endTransmission();
delay(10);
// Exit CFG_UPDATE with reinit
bq27220_writeControl(0x0091);
delay(200);
Serial.println("BQ27220: Design Energy updated, exited CFG_UPDATE");
// Exit with reinit since we actually changed data
bq27220_writeControl(0x0091); // EXIT_CFG_UPDATE_REINIT
delay(200);
Serial.println("BQ27220: Design Energy written, exited CFG_UPDATE");
} else {
// DC=2000, DE=7400, Update Status=0x00, but FCC is stuck at 3000.
// Diagnostic scan found the culprits:
// 0x9106 = Qmax Cell 0 (IT Cfg class) — the raw capacity the
// gauge uses for FCC calculation. Factory default 3000.
// 0x929D = Stored FCC reference (Gas Gauging class, 2 bytes
// before Design Capacity). Also stuck at 3000.
//
// Fix: overwrite both with designCapacity_mAh (2000).
Serial.printf("BQ27220: DE correct (%d mWh) — fixing Qmax + stored FCC\n", currentDE);
// --- Helper lambda for MAC data memory 2-byte write ---
// Reads old value + checksum, computes differential checksum, writes new value.
auto writeDM16 = [](uint16_t addr, uint16_t newVal) -> bool {
// Select address
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x3E);
Wire.write(addr & 0xFF);
Wire.write((addr >> 8) & 0xFF);
Wire.endTransmission();
delay(10);
uint8_t oldMSB = bq27220_read8(0x40);
uint8_t oldLSB = bq27220_read8(0x41);
uint8_t oldChk = bq27220_read8(0x60);
uint8_t dLen = bq27220_read8(0x61);
uint16_t oldVal = (oldMSB << 8) | oldLSB;
if (oldVal == newVal) {
Serial.printf("BQ27220: [0x%04X] already %d, skip\n", addr, newVal);
return true; // already correct
}
uint8_t newMSB = (newVal >> 8) & 0xFF;
uint8_t newLSB = newVal & 0xFF;
uint8_t temp = (255 - oldChk - oldMSB - oldLSB);
uint8_t newChk = 255 - ((temp + newMSB + newLSB) & 0xFF);
Serial.printf("BQ27220: [0x%04X] %d -> %d\n", addr, oldVal, newVal);
// Write new value
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x3E);
Wire.write(addr & 0xFF);
Wire.write((addr >> 8) & 0xFF);
Wire.write(newMSB);
Wire.write(newLSB);
Wire.endTransmission();
delay(5);
// Write checksum
Wire.beginTransmission(BQ27220_I2C_ADDR);
Wire.write(0x60);
Wire.write(newChk);
Wire.write(dLen);
Wire.endTransmission();
delay(10);
return true;
};
// Overwrite Qmax Cell 0 (IT Cfg) — this is what FCC is derived from
writeDM16(0x9106, designCapacity_mAh);
// Overwrite stored FCC reference (Gas Gauging, 2 bytes before DC)
writeDM16(0x929D, designCapacity_mAh);
// Exit with reinit to apply the new values
bq27220_writeControl(0x0091); // EXIT_CFG_UPDATE_REINIT
delay(200);
Serial.println("BQ27220: Qmax + stored FCC updated, exited CFG_UPDATE");
}
} else {
Serial.println("BQ27220: Failed to enter CFG_UPDATE for DE fix");
bq27220_writeControl(0x0092); // Exit cleanly
Serial.println("BQ27220: Failed to enter CFG_UPDATE for DE check");
}
// Seal
bq27220_writeControl(0x0030);
// Seal first, then issue RESET.
// RESET forces the gauge to fully reinitialize its Impedance Track
// algorithm and recalculate FCC from the current DC/DE values.
// This is the actual fix when DC and DE are correct but FCC is stuck.
bq27220_writeControl(0x0030); // SEAL
delay(5);
Serial.println("BQ27220: Issuing RESET to force FCC recalculation...");
bq27220_writeControl(0x0041); // RESET
delay(2000); // Full reset needs generous settle time
fcc = bq27220_read16(BQ27220_REG_FULL_CAP);
Serial.printf("BQ27220: FCC after Design Energy update: %d mAh\n", fcc);
Serial.printf("BQ27220: FCC after RESET: %d mAh (target <= %d)\n", fcc, designCapacity_mAh);
if (fcc > designCapacity_mAh * 3 / 2) {
// RESET didn't fix FCC — the gauge IT algorithm is stubbornly
// retaining its learned value. This typically resolves after one
// full charge/discharge cycle. Software clamp in
// getFullChargeCapacity() ensures correct display regardless.
Serial.printf("BQ27220: FCC still stale at %d — software clamp active\n", fcc);
}
}
return true;
}
@@ -434,6 +511,17 @@ bool TDeckBoard::configureFuelGauge(uint16_t designCapacity_mAh) {
bq27220_writeControl(0x0030);
delay(5);
// Step 7: Force full gauge RESET to reinitialize FCC from new DC/DE.
// Without this, the Impedance Track algorithm retains the old FCC
// (often 3000 mAh from factory) until a full charge/discharge cycle.
bq27220_writeControl(0x0041); // RESET
delay(1000); // Gauge needs time to fully reinitialize
// Re-verify after hard reset
verifyDC = bq27220_read16(BQ27220_REG_DESIGN_CAP);
newFCC = bq27220_read16(BQ27220_REG_FULL_CAP);
Serial.printf("BQ27220: Post-RESET DC=%d FCC=%d mAh\n", verifyDC, newFCC);
return verifyDC == designCapacity_mAh;
#else
return false;
@@ -474,7 +562,12 @@ uint16_t TDeckBoard::getRemainingCapacity() {
uint16_t TDeckBoard::getFullChargeCapacity() {
#if HAS_BQ27220
return bq27220_read16(BQ27220_REG_FULL_CAP);
uint16_t fcc = bq27220_read16(BQ27220_REG_FULL_CAP);
// Clamp to design capacity — the gauge may report a stale factory FCC
// (e.g. 3000 mAh) until it completes a full learning cycle. Never let
// the reported FCC exceed what the actual cell can hold.
if (fcc > BQ27220_DESIGN_CAPACITY_MAH) fcc = BQ27220_DESIGN_CAPACITY_MAH;
return fcc;
#else
return 0;
#endif