[pcf85063] Convert the weekday to and from the chip's 0-6 range (#20736)

esphome/components/pcf85063/pcf85063.cpp

@@ -37,7 +37,8 @@ void PCF85063Component::read_time() {
       .second = uint8_t(pcf85063_.reg.second + 10 * pcf85063_.reg.second_10),
       .minute = uint8_t(pcf85063_.reg.minute + 10u * pcf85063_.reg.minute_10),
       .hour = uint8_t(pcf85063_.reg.hour + 10u * pcf85063_.reg.hour_10),
-      .day_of_week = uint8_t(pcf85063_.reg.weekday),
+      // The chip counts weekdays 0-6 from Sunday, ESPTime counts 1-7
+      .day_of_week = uint8_t(this->pcf85063_.reg.weekday + 1),
       .day_of_month = uint8_t(pcf85063_.reg.day + 10u * pcf85063_.reg.day_10),
       .month = uint8_t(pcf85063_.reg.month + 10u * pcf85063_.reg.month_10),
       .year = uint16_t(pcf85063_.reg.year + 10u * pcf85063_.reg.year_10 + 2000),
@@ -62,7 +63,7 @@ void PCF85063Component::write_time() {
   pcf85063_.reg.month_10 = now.month / 10;
   pcf85063_.reg.day = now.day_of_month % 10;
   pcf85063_.reg.day_10 = now.day_of_month / 10;
-  pcf85063_.reg.weekday = now.day_of_week;
+  this->pcf85063_.reg.weekday = now.day_of_week - 1;
   pcf85063_.reg.hour = now.hour % 10;
   pcf85063_.reg.hour_10 = now.hour / 10;
   pcf85063_.reg.minute = now.minute % 10;

tests/components/pcf85063/__init__.py

@@ -0,0 +1,6 @@
+from tests.testing_helpers import ComponentManifestOverride
+
+
+def override_manifest(manifest: ComponentManifestOverride) -> None:
+    # The driver lives in the time platform, so pull in what it builds against.
+    manifest.dependencies = manifest.dependencies + ["i2c", "time"]

tests/components/pcf85063/test_pcf85063.cpp

@@ -0,0 +1,77 @@
+#include <gtest/gtest.h>
+
+#include <array>
+#include <ctime>
+
+#include "esphome/components/pcf85063/pcf85063.h"
+#include "esphome/core/time.h"
+
+namespace esphome::pcf85063::testing {
+
+static constexpr uint8_t ADDRESS = 0x51;
+static constexpr uint8_t WEEKDAYS_REG = 0x08;
+static constexpr uint8_t CHIP_DAYS_PER_WEEK = 7;  // The chip counts weekdays 0-6, Sunday = 0
+
+// The chip's 18 registers behind an address pointer that moves on after every byte.
+class RegisterBus final : public i2c::I2CBus {
+ public:
+  i2c::ErrorCode write_readv(uint8_t address, const uint8_t *data, size_t size, uint8_t *out,
+                             size_t out_size) override {
+    EXPECT_EQ(address, ADDRESS);
+    if (size != 0) {
+      this->pointer_ = data[0];
+      for (size_t i = 1; i < size; i++)
+        this->registers[this->next_()] = data[i];
+    }
+    for (size_t i = 0; i < out_size; i++)
+      out[i] = this->registers[this->next_()];
+    return i2c::ERROR_OK;
+  }
+
+  std::array<uint8_t, 18> registers{};
+
+ protected:
+  size_t next_() { return this->pointer_++ % this->registers.size(); }
+
+  uint8_t pointer_{0};
+};
+
+// write_time() takes the host's current time, so reading it back never changes the host clock.
+class PCF85063Test : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    this->rtc_.set_i2c_bus(&this->bus_);
+    this->rtc_.set_i2c_address(ADDRESS);
+    this->rtc_.add_on_time_sync_callback([this]() { ++this->syncs_; });
+    this->rtc_.setup();
+  }
+
+  RegisterBus bus_;
+  PCF85063Component rtc_;
+  unsigned syncs_{0};
+};
+
+TEST_F(PCF85063Test, WriteTimeStoresTheChipsWeekday) {
+  // Read the clock on both sides of the write, in case UTC midnight falls in between.
+  const int before = ESPTime::from_epoch_utc(::time(nullptr)).day_of_week - 1;
+  this->rtc_.write_time();
+  const int after = ESPTime::from_epoch_utc(::time(nullptr)).day_of_week - 1;
+  const int stored = this->bus_.registers[WEEKDAYS_REG];
+  EXPECT_TRUE(stored == before || stored == after) << "stored " << stored << ", expected " << before;
+}
+
+// After a write the chip keeps counting on its own and goes from Saturday (6) back to Sunday (0) at midnight.
+// Seven steps from the written value visit every weekday once, and each has to read back as a valid time.
+// Only the weekday moves, so the time read back is still the host's time.
+TEST_F(PCF85063Test, WeekdayRoundTripsThroughSundayAndSaturday) {
+  this->rtc_.write_time();
+  uint8_t &weekday = this->bus_.registers[WEEKDAYS_REG];
+  for (uint8_t day = 0; day < CHIP_DAYS_PER_WEEK; day++) {
+    weekday = (weekday + 1) % CHIP_DAYS_PER_WEEK;
+    const unsigned syncs_before = this->syncs_;
+    this->rtc_.read_time();
+    EXPECT_EQ(this->syncs_, syncs_before + 1) << "chip weekday " << unsigned(weekday);
+  }
+}
+
+}  // namespace esphome::pcf85063::testing