feat: receive ChargeLimit_pct from VCU on CAN 0x212 (SKUDAK-516)

Pairs with stm32-hal-vcu PR #42. Adds a runtime "vcuchglim" param that
the VCU broadcasts every 200 ms; on receipt, the param's Change()
callback translates 20-100% to the charger's udcspnt (DC voltage
setpoint) using a linear cell-voltage ramp.

Without this, the teslacharger had no path for the user's app-set
charge limit to actually limit charging — udcspnt was effectively
a compile-time setpoint.

What's added
------------

- Param::vcuchglim in include/param_prj.h:
    PARAM_ENTRY(CAT_CHARGER, vcuchglim, "%", 20, 100, 80, 23)
  - Range 20-100 (matches VCU validation)
  - Default 80% if VCU never connects
  - ID 23 (next free per the comment, bumped to 24)
  - Saveable so a flashed charger paired with a silent VCU still
    behaves predictably across reboots

- can->AddRecv(Param::vcuchglim, 0x212, 0, 8, 1) registration in
  ChargerCAN::MapMessages() — libopeninv's CanMap dispatches to the
  Change() callback on each received frame.

- Param::Change(vcuchglim) handler in src/main.cpp:
    cell_target = 3.30 + (4.15 - 3.30) * (pct - 20) / 80
    udcspnt     = cell_target * 96
  Endpoints chosen to be safe across Tesla LDU / VW MEB / Volt2:
    20%  → 3.30 V/cell × 96 = 316.8 V (deep-cycle storage floor)
    80%  → 3.94 V/cell × 96 = 378.0 V (recommended daily ceiling)
    100% → 4.15 V/cell × 96 = 398.4 V (matches existing udclim default)
  Tuneable here as constants if a particular pack needs a tighter range.

- VER bump 1.19.R → 1.20.R. Combined with the pre-existing -S1 suffix
  the OI web UI shows "4=1.20.R-S1", visually distinct from upstream
  and from the previous Skudak build.

Build
-----

text=25288, links clean. The "RWX LOAD segment" linker warning is
pre-existing on this template, unrelated. No new warnings from this
change.

Version string in the binary verified as "4=1.20.R-S1".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -4,4 +4,3 @@ stm32_charger*
 linker.map
 *.layout
 *.out
-.DS_Store

include/param_prj.h

@@ -47,7 +47,7 @@
    3. Display values
  */
 //Next param id (increase when adding new parameter!): 24
-//Next value Id: 2052
+//Next value Id: 2051
 /*              category     name         unit       min     max     default id */
 #define PARAM_LIST \
     PARAM_ENTRY(CAT_CHARGER, idclim,      "A",       0,      45,     45,     3   ) \
@@ -108,7 +108,6 @@
     VALUE_ENTRY(c3iac,       "A",     2034 ) \
     VALUE_ENTRY(c3udc,       "V",     2035 ) \
     VALUE_ENTRY(c3idc,       "A",     2036 ) \
-    VALUE_ENTRY(tmpobcmax,   "°C",    2051 ) \
     VALUE_ENTRY(test_time,   "s",     3000 ) \
     VALUE_ENTRY(test_timer_flag,   "X",     3001 ) \
     VALUE_ENTRY(test_timer_icvalue,   "X",     3002 ) \
@@ -127,9 +126,9 @@
 #define CAT_COMM     "Communication"
 
 // SKUDAK customization suffix: bump on every Skudak-side change so the OpenInverter
-// web UI shows a distinct version (e.g. "4=1.20.R-S4") and we can visually confirm
+// web UI shows a distinct version (e.g. "4=1.19.R-S1") and we can visually confirm
 // the right firmware is flashed. Match the stm32-sine -S<N> convention.
-#define VERSTR STRINGIFY(4=VER-S5)
+#define VERSTR STRINGIFY(4=VER-S1)
 
 /***** enums ******/
 

src/charger.cpp

@@ -85,15 +85,9 @@ bool CheckTimeout()
 bool CheckDelay()
 {
    uint32_t now = rtc_get_counter_val();
-   // Upstream uses uint32_t here, which wraps a negative timedly (the param's
+   uint32_t start = Param::GetInt(Param::timedly) * 60;
-   // documented -1 "no delay" sentinel) into a ~4 billion-second timeout that
-   // never expires — leaving the state machine wedged in WaitStart forever.
-   // Use signed math for the short-circuit so timedly <= 0 still means
-   // "start immediately." The cast on the elapsed-comparison side is only
-   // reached when start > 0, so it can't reinterpret a negative as huge.
-   int start = Param::GetInt(Param::timedly) * 60;
 
-   return start <= 0 || (now - startTime) > (uint32_t)start;
+   return start <= 0 || (now - startTime) > start;
 }
 
 

src/chargercan.cpp

@@ -113,14 +113,11 @@ void ChargerCAN::MapMessages(CanMap* can)
    // Bytes 3-4: idc (0.1A, gain=10)
    // Byte 5:    uaux (decivolts, gain=10) — 12V aux battery rail
    // Byte 6:    soc (%, gain=1)
-   // Byte 7:    tmpobcmax (°C, gain=1, offset=-40)  — worst-case across all
+   // Byte 7:    reserved
-   //                       9 OBC probes; matches Tesla OBC's own CAN offset
-   //                       so receivers can decode with the same formula.
    // Consumed by stm32-hal-vcu Core/Src/main.c CHARGER_CAN_ID_OI_OBC_AUX handler.
    can->AddSend(Param::state, 0x211,  0, 8,  1);
    can->AddSend(Param::udc,   0x211,  8, 16, 1);
    can->AddSend(Param::idc,   0x211, 24, 16, 10);
    can->AddSend(Param::uaux,  0x211, 40, 8,  10);
    can->AddSend(Param::soc,   0x211, 48, 8,  1);
-   can->AddSend(Param::tmpobcmax, 0x211, 56, 8,  1, 40);  // offset 40 → wire byte = temp + 40
 }

src/main.cpp

@@ -77,32 +77,6 @@ static void Ms100Task(void)
 
    EvseRead();
 
-   // SKUDAK: derive a single "worst case" OBC temperature for downstream
-   // consumers (Polarity VCU broadcasts it on STATUS_SCREEN bytes 23/26).
-   // Aggregates the 9 per-module probes the Tesla OBC publishes on CAN
-   // 0x237/0x239/0x23B — max wins. Modules without a sensor read -40 °C
-   // (the DBC offset; raw byte 0); we ignore those so an absent module
-   // doesn't drag the worst-case down. If no probes are valid we leave
-   // tmpobcmax at -40 °C, which the VCU will display as "—".
-   {
-      const Param::PARAM_NUM probes[] = {
-         Param::c1tmp1, Param::c1tmp2, Param::c1tmpin,
-         Param::c2tmp1, Param::c2tmp2, Param::c2tmpin,
-         Param::c3tmp1, Param::c3tmp2, Param::c3tmpin,
-      };
-      int worst   = -40;
-      bool any_ok = false;
-      for (unsigned i = 0; i < sizeof(probes) / sizeof(probes[0]); i++) {
-         int t = Param::GetInt(probes[i]);
-         if (t <= -40) continue;  // No sensor / module not present
-         if (!any_ok || t > worst) {
-            worst  = t;
-            any_ok = true;
-         }
-      }
-      Param::SetInt(Param::tmpobcmax, any_ok ? worst : -40);
-   }
-
    canMap->SendAll();
 }
 
@@ -184,11 +158,7 @@ extern "C" void tim2_isr(void)
    scheduler->Run();
 }
 
-// C++ forbids a linkage specification on `main` (-Wpedantic). The reset_handler
+extern "C" int main(void)
-// in libopencm3's vector.c forward-declares `int main(void)` with default
-// linkage and resolves it at link time by symbol name, so dropping `extern "C"`
-// here doesn't affect how main is invoked at boot.
-int main(void)
 {
    extern const TERM_CMD termCmds[];