diff --git a/src/utility/M5IOE1_Class.cpp b/src/utility/M5IOE1_Class.cpp
index 591c261..5fb8d9c 100644
--- a/src/utility/M5IOE1_Class.cpp
+++ b/src/utility/M5IOE1_Class.cpp
@@ -109,10 +109,10 @@ namespace m5
     return true;
   }
 
-  void M5IOE1_Class::setPwmFrequency(std::uint16_t frequency)
+  bool M5IOE1_Class::setPwmFrequency(std::uint16_t frequency)
   {
     std::uint8_t data[2] = { static_cast<std::uint8_t>(frequency & 0xFF), static_cast<std::uint8_t>(frequency >> 8) };
-    writeRegister(M5IOE1_REG_PWM_FREQ_L, data, sizeof(data));
+    return writeRegister(M5IOE1_REG_PWM_FREQ_L, data, sizeof(data));
   }
 
   bool M5IOE1_Class::setPwmDutyPercent(pwm_channel_t channel, std::uint32_t duty,
diff --git a/src/utility/M5IOE1_Class.hpp b/src/utility/M5IOE1_Class.hpp
index d073aac..be1568b 100644
--- a/src/utility/M5IOE1_Class.hpp
+++ b/src/utility/M5IOE1_Class.hpp
@@ -58,7 +58,10 @@ namespace m5
     bool digitalRead(uint8_t pin) override;
     bool getInputLevel(uint8_t pin, bool* level) override;
 
-    void setPwmFrequency(std::uint16_t frequency);
+    /// set the PWM frequency in Hz.
+    /// @note The frequency is shared by all PWM channels, so changing it also
+    /// changes a channel that is already running.
+    bool setPwmFrequency(std::uint16_t frequency);
 
     /// set PWM duty in percent.
     /// @param channel PWM channel (pwm_ch1 - pwm_ch4).