feat(core): split temperature lookup tables for charging and discharging profile.

Trezor/Trezor firmware

150e73a2 View source ↗

Public commit record

What the developer wrote

Authored by kopecdav

62/100 · Adequate

feat(core): split temperature lookup tables for charging and discharging profile.

[no changelog]

✓ Specific, descriptive subject✓ Names a concrete action or component✓ Uses a recognizable type or scope! No meaningful explanatory body

The short version

What changed, and why it matters

This commit updates the battery fuel gauge code in Trezor hardware wallets so that it uses separate temperature lookup tables when the battery is charging versus when it is discharging. Previously, the same temperature table was used for both states. This is a routine calibration/modeling improvement, not a security fix.

Recommended action

No security action required. Treat as normal firmware maintenance.

Security signals we found

No strong security signals were identified.

Technical analysis

Evidence from the diff

The change is localized to battery_model.c. It replaces the single BATTERY_TEMP_POINTS array with two mode-specific arrays (BATTERY_TEMP_POINTS_DISCHG and BATTERY_TEMP_POINTS_CHG) in four functions: battery_total_capacity, battery_ocv, battery_ocv_slope, and battery_soc. The interpolation logic is otherwise unchanged. There is no input validation change, bounds-checking change, memory safety change, or cryptographic change. The commit message is a feature description with no security framing.

Changed components

core/embed/sys/power_manager/fuel_gauge/battery_model.c

Inspect captured patch +36 / −21

diff --git a/core/embed/sys/power_manager/fuel_gauge/battery_model.c b/core/embed/sys/power_manager/fuel_gauge/battery_model.c
index 286680d92..6882207f6 100644
--- a/core/embed/sys/power_manager/fuel_gauge/battery_model.c
+++ b/core/embed/sys/power_manager/fuel_gauge/battery_model.c
@@ -121,23 +121,26 @@ float battery_rint(float temperature) {
 }
 
 float battery_total_capacity(float temperature, bool discharging_mode) {
+  // Select appropriate temperature array based on mode
+  const float* temp_points =
+      discharging_mode ? BATTERY_TEMP_POINTS_DISCHG : BATTERY_TEMP_POINTS_CHG;
+
   // Handle out-of-bounds temperatures
-  if (temperature <= BATTERY_TEMP_POINTS[0]) {
+  if (temperature <= temp_points[0]) {
     return BATTERY_CAPACITY[0][discharging_mode ? 0 : 1];
   }
 
-  if (temperature >= BATTERY_TEMP_POINTS[BATTERY_NUM_TEMP_POINTS - 1]) {
+  if (temperature >= temp_points[BATTERY_NUM_TEMP_POINTS - 1]) {
     return BATTERY_CAPACITY[BATTERY_NUM_TEMP_POINTS - 1]
                            [discharging_mode ? 0 : 1];
   }
 
   // Find temperature bracket
   for (int i = 0; i < BATTERY_NUM_TEMP_POINTS - 1; i++) {
-    if (temperature < BATTERY_TEMP_POINTS[i + 1]) {
+    if (temperature < temp_points[i + 1]) {
       return linear_interpolate(
-          temperature, BATTERY_TEMP_POINTS[i],
-          BATTERY_CAPACITY[i][discharging_mode ? 0 : 1],
-          BATTERY_TEMP_POINTS[i + 1],
+          temperature, temp_points[i],
+          BATTERY_CAPACITY[i][discharging_mode ? 0 : 1], temp_points[i + 1],
           BATTERY_CAPACITY[i + 1][discharging_mode ? 0 : 1]);
     }
   }
@@ -159,14 +162,18 @@ float battery_ocv(float soc, float temperature, bool discharging_mode) {
   // Clamp SOC to valid range
   soc = (soc < 0.0f) ? 0.0f : ((soc > 1.0f) ? 1.0f : soc);
 
+  // Select appropriate temperature array based on mode
+  const float* temp_points =
+      discharging_mode ? BATTERY_TEMP_POINTS_DISCHG : BATTERY_TEMP_POINTS_CHG;
+
   // Handle out-of-bounds temperatures
-  if (temperature <= BATTERY_TEMP_POINTS[0]) {
+  if (temperature <= temp_points[0]) {
     const float* params = discharging_mode ? BATTERY_OCV_DISCHARGE_PARAMS[0]
                                            : BATTERY_OCV_CHARGE_PARAMS[0];
     return calc_ocv(params, soc);
   }
 
-  if (temperature >= BATTERY_TEMP_POINTS[BATTERY_NUM_TEMP_POINTS - 1]) {
+  if (temperature >= temp_points[BATTERY_NUM_TEMP_POINTS - 1]) {
     const float* params =
         discharging_mode
             ? BATTERY_OCV_DISCHARGE_PARAMS[BATTERY_NUM_TEMP_POINTS - 1]
@@ -176,7 +183,7 @@ float battery_ocv(float soc, float temperature, bool discharging_mode) {
 
   // Find temperature bracket and interpolate
   for (int i = 0; i < BATTERY_NUM_TEMP_POINTS - 1; i++) {
-    if (temperature < BATTERY_TEMP_POINTS[i + 1]) {
+    if (temperature < temp_points[i + 1]) {
       const float* params_low = discharging_mode
                                     ? BATTERY_OCV_DISCHARGE_PARAMS[i]
                                     : BATTERY_OCV_CHARGE_PARAMS[i];
@@ -188,8 +195,8 @@ float battery_ocv(float soc, float temperature, bool discharging_mode) {
       float ocv_low = calc_ocv(params_low, soc);
       float ocv_high = calc_ocv(params_high, soc);
 
-      return linear_interpolate(temperature, BATTERY_TEMP_POINTS[i], ocv_low,
-                                BATTERY_TEMP_POINTS[i + 1], ocv_high);
+      return linear_interpolate(temperature, temp_points[i], ocv_low,
+                                temp_points[i + 1], ocv_high);
     }
   }
 
@@ -203,14 +210,18 @@ float battery_ocv_slope(float soc, float temperature, bool discharging_mode) {
   // Clamp SOC to valid range
   soc = (soc < 0.0f) ? 0.0f : ((soc > 1.0f) ? 1.0f : soc);
 
+  // Select appropriate temperature array based on mode
+  const float* temp_points =
+      discharging_mode ? BATTERY_TEMP_POINTS_DISCHG : BATTERY_TEMP_POINTS_CHG;
+
   // Handle out-of-bounds temperatures
-  if (temperature <= BATTERY_TEMP_POINTS[0]) {
+  if (temperature <= temp_points[0]) {
     const float* params = discharging_mode ? BATTERY_OCV_DISCHARGE_PARAMS[0]
                                            : BATTERY_OCV_CHARGE_PARAMS[0];
     return calc_ocv_slope(params, soc);
   }
 
-  if (temperature >= BATTERY_TEMP_POINTS[BATTERY_NUM_TEMP_POINTS - 1]) {
+  if (temperature >= temp_points[BATTERY_NUM_TEMP_POINTS - 1]) {
     const float* params =
         discharging_mode
             ? BATTERY_OCV_DISCHARGE_PARAMS[BATTERY_NUM_TEMP_POINTS - 1]
@@ -220,7 +231,7 @@ float battery_ocv_slope(float soc, float temperature, bool discharging_mode) {
 
   // Find temperature bracket and interpolate
   for (int i = 0; i < BATTERY_NUM_TEMP_POINTS - 1; i++) {
-    if (temperature < BATTERY_TEMP_POINTS[i + 1]) {
+    if (temperature < temp_points[i + 1]) {
       const float* params_low = discharging_mode
                                     ? BATTERY_OCV_DISCHARGE_PARAMS[i]
                                     : BATTERY_OCV_CHARGE_PARAMS[i];
@@ -232,8 +243,8 @@ float battery_ocv_slope(float soc, float temperature, bool discharging_mode) {
       float slope_low = calc_ocv_slope(params_low, soc);
       float slope_high = calc_ocv_slope(params_high, soc);
 
-      return linear_interpolate(temperature, BATTERY_TEMP_POINTS[i], slope_low,
-                                BATTERY_TEMP_POINTS[i + 1], slope_high);
+      return linear_interpolate(temperature, temp_points[i], slope_low,
+                                temp_points[i + 1], slope_high);
     }
   }
 
@@ -244,14 +255,18 @@ float battery_ocv_slope(float soc, float temperature, bool discharging_mode) {
 }
 
 float battery_soc(float ocv, float temperature, bool discharging_mode) {
+  // Select appropriate temperature array based on mode
+  const float* temp_points =
+      discharging_mode ? BATTERY_TEMP_POINTS_DISCHG : BATTERY_TEMP_POINTS_CHG;
+
   // Handle out-of-bounds temperatures
-  if (temperature <= BATTERY_TEMP_POINTS[0]) {
+  if (temperature <= temp_points[0]) {
     const float* params = discharging_mode ? BATTERY_OCV_DISCHARGE_PARAMS[0]
                                            : BATTERY_OCV_CHARGE_PARAMS[0];
     return calc_soc_from_ocv(params, ocv);
   }
 
-  if (temperature >= BATTERY_TEMP_POINTS[BATTERY_NUM_TEMP_POINTS - 1]) {
+  if (temperature >= temp_points[BATTERY_NUM_TEMP_POINTS - 1]) {
     const float* params =
         discharging_mode
             ? BATTERY_OCV_DISCHARGE_PARAMS[BATTERY_NUM_TEMP_POINTS - 1]
@@ -261,7 +276,7 @@ float battery_soc(float ocv, float temperature, bool discharging_mode) {
 
   // Find temperature bracket and interpolate
   for (int i = 0; i < BATTERY_NUM_TEMP_POINTS - 1; i++) {
-    if (temperature < BATTERY_TEMP_POINTS[i + 1]) {
+    if (temperature < temp_points[i + 1]) {
       const float* params_low = discharging_mode
                                     ? BATTERY_OCV_DISCHARGE_PARAMS[i]
                                     : BATTERY_OCV_CHARGE_PARAMS[i];
@@ -273,8 +288,8 @@ float battery_soc(float ocv, float temperature, bool discharging_mode) {
       float soc_low = calc_soc_from_ocv(params_low, ocv);
       float soc_high = calc_soc_from_ocv(params_high, ocv);
 
-      return linear_interpolate(temperature, BATTERY_TEMP_POINTS[i], soc_low,
-                                BATTERY_TEMP_POINTS[i + 1], soc_high);
+      return linear_interpolate(temperature, temp_points[i], soc_low,
+                                temp_points[i + 1], soc_high);
     }
   }

Risk score

Why this scored 15/100

Our methodology →

Potential impact 0/30

Exploitability 0/25

Stealth signal 0/15

Affected reach 0/15

Confidence 10/10

Evidence quality 5/5

Human-validated context

Community notes

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What the developer wrote

What changed, and why it matters

Security signals we found

Evidence from the diff

Changed components

Why this scored 15/100

Community notes

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