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BMW i3: Split up transmit CAN to avoid overloads #2290

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BMW i3: Split up transmit CAN to avoid overloads #2290

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21a79ee
Split up transmit CAN to avoid overloads
dalathegreat May 4, 2026
fbd16e2
Merge branch 'main' into bugfix/bmwi3-split-transmit
dalathegreat May 4, 2026
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21 changes: 13 additions & 8 deletions Software/src/battery/BMW-I3-BATTERY.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -313,10 +313,15 @@ void BmwI3Battery::handle_incoming_can_frame(CAN_frame rx_frame) {
}

void BmwI3Battery::transmit_can(unsigned long currentMillis) {
// Ensure we only send one message branch at a time, to reduce worst-case runtime
static int transmitPhase = -1;
if (++transmitPhase >= 8) {
transmitPhase = 0;
}

if (battery_awake) {
//Send 20ms message
if (currentMillis - previousMillis20 >= INTERVAL_20_MS) {
if (currentMillis - previousMillis20 >= INTERVAL_20_MS && transmitPhase == 0) {
previousMillis20 = currentMillis;

if (startup_counter_contactor < 160) {
Expand Down Expand Up @@ -344,7 +349,7 @@ void BmwI3Battery::transmit_can(unsigned long currentMillis) {
}

// Send 100ms CAN Message
if (currentMillis - previousMillis100 >= INTERVAL_100_MS) {
if (currentMillis - previousMillis100 >= INTERVAL_100_MS && transmitPhase == 1) {
previousMillis100 = currentMillis;

BMW_12F.data.u8[1] = ((BMW_12F.data.u8[1] & 0xF0) + alive_counter_100ms);
Expand All @@ -355,7 +360,7 @@ void BmwI3Battery::transmit_can(unsigned long currentMillis) {
transmit_can_frame(&BMW_12F);
}
// Send 200ms CAN Message
if (currentMillis - previousMillis200 >= INTERVAL_200_MS) {
if (currentMillis - previousMillis200 >= INTERVAL_200_MS && transmitPhase == 2) {
previousMillis200 = currentMillis;

BMW_19B.data.u8[1] = ((BMW_19B.data.u8[1] & 0xF0) + alive_counter_200ms);
Expand Down Expand Up @@ -398,7 +403,7 @@ void BmwI3Battery::transmit_can(unsigned long currentMillis) {
}
}
// Send 500ms CAN Message
if (currentMillis - previousMillis500 >= INTERVAL_500_MS) {
if (currentMillis - previousMillis500 >= INTERVAL_500_MS && transmitPhase == 3) {
previousMillis500 = currentMillis;

BMW_30B.data.u8[1] = ((BMW_30B.data.u8[1] & 0xF0) + alive_counter_500ms);
Expand All @@ -409,14 +414,14 @@ void BmwI3Battery::transmit_can(unsigned long currentMillis) {
transmit_can_frame(&BMW_30B);
}
// Send 640ms CAN Message
if (currentMillis - previousMillis640 >= INTERVAL_640_MS) {
if (currentMillis - previousMillis640 >= INTERVAL_640_MS && transmitPhase == 4) {
previousMillis640 = currentMillis;

transmit_can_frame(&BMW_512); // Keep BMS alive
transmit_can_frame(&BMW_5F8);
}
// Send 1000ms CAN Message
if (currentMillis - previousMillis1000 >= INTERVAL_1_S) {
if (currentMillis - previousMillis1000 >= INTERVAL_1_S && transmitPhase == 5) {
previousMillis1000 = currentMillis;
//BMW_328 byte0-3 = Second Counter (T_SEC_COU_REL) time_second_counter_relative
// This signal shows the time in seconds since the system time was started (typically in the factory)
Expand Down Expand Up @@ -519,7 +524,7 @@ void BmwI3Battery::transmit_can(unsigned long currentMillis) {
}
}
// Send 5000ms CAN Message
if (currentMillis - previousMillis5000 >= INTERVAL_5_S) {
if (currentMillis - previousMillis5000 >= INTERVAL_5_S && transmitPhase == 6) {
previousMillis5000 = currentMillis;

BMW_3FC.data.u8[1] = ((BMW_3FC.data.u8[1] & 0xF0) + alive_counter_5000ms);
Expand All @@ -539,7 +544,7 @@ void BmwI3Battery::transmit_can(unsigned long currentMillis) {
}
}
// Send 10000ms CAN Message
if (currentMillis - previousMillis10000 >= INTERVAL_10_S) {
if (currentMillis - previousMillis10000 >= INTERVAL_10_S && transmitPhase == 7) {
previousMillis10000 = currentMillis;

transmit_can_frame(&BMW_3E5); //Order comes from CAN logs
Expand Down
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