diff --git a/src/rp2_common/hardware_clocks/include/hardware/clocks.h b/src/rp2_common/hardware_clocks/include/hardware/clocks.h
index 68f4b1a50..e238e841c 100644
--- a/src/rp2_common/hardware_clocks/include/hardware/clocks.h
+++ b/src/rp2_common/hardware_clocks/include/hardware/clocks.h
@@ -399,7 +399,18 @@ void clocks_enable_resus(resus_callback_t resus_callback);
 /*! \brief Output an optionally divided clock to the specified gpio pin.
  *  \ingroup hardware_clocks
  *
- * \param gpio The GPIO pin to output the clock to. Valid GPIOs are: 21, 23, 24, 25. These GPIOs are connected to the GPOUT0-3 clock generators.
+ * \if rp2040_specific
+ * On RP2040 valid GPIOs are 21, 23, 24, 25.
+ * These GPIOs are connected to the GPOUT0-3 clock generators.
+ * \endif
+ * \if rp2350_specific
+ * On RP2350 valid GPIOs are 13, 15, 21, 23, 24, 25.
+ * GPIOs 13 and 21 are connected to the GPOUT0 clock generator.
+ * GPIOs 15 and 23 are connected to the GPOUT1 clock generator.
+ * GPIOs 24 and 25 are connected to the GPOUT2-3 clock generators.
+ * \endif
+ *
+ * \param gpio The GPIO pin to output the clock to.
  * \param src  The source clock. See the register field CLOCKS_CLK_GPOUT0_CTRL_AUXSRC for a full list. The list is the same for each GPOUT clock generator.
  * \param div_int  The integer part of the value to divide the source clock by. This is useful to not overwhelm the GPIO pin with a fast clock. This is in range of 1..2^24-1 on RP2040
  *                 and 1..2^16-1 on RP2350
@@ -410,7 +421,18 @@ void clock_gpio_init_int_frac16(uint gpio, uint src, uint32_t div_int, uint16_t
 /*! \brief Output an optionally divided clock to the specified gpio pin.
  *  \ingroup hardware_clocks
  *
- * \param gpio The GPIO pin to output the clock to. Valid GPIOs are: 21, 23, 24, 25. These GPIOs are connected to the GPOUT0-3 clock generators.
+ *  * \if rp2040_specific
+ * On RP2040 valid GPIOs are 21, 23, 24, 25.
+ * These GPIOs are connected to the GPOUT0-3 clock generators.
+ * \endif
+ * \if rp2350_specific
+ * On RP2350 valid GPIOs are 13, 15, 21, 23, 24, 25.
+ * GPIOs 13 and 21 are connected to the GPOUT0 clock generator.
+ * GPIOs 15 and 23 are connected to the GPOUT1 clock generator.
+ * GPIOs 24 and 25 are connected to the GPOUT2-3 clock generators.
+ * \endif
+ *
+ * \param gpio The GPIO pin to output the clock to.
  * \param src  The source clock. See the register field CLOCKS_CLK_GPOUT0_CTRL_AUXSRC for a full list. The list is the same for each GPOUT clock generator.
  * \param div_int  The integer part of the value to divide the source clock by. This is useful to not overwhelm the GPIO pin with a fast clock. This is in range of 1..2^24-1 on RP2040
  *                 and 1..2^16-1 on RP2350
@@ -428,7 +450,18 @@ static inline void clock_gpio_init_int_frac(uint gpio, uint src, uint32_t div_in
 /*! \brief Output an optionally divided clock to the specified gpio pin.
  *  \ingroup hardware_clocks
  *
- * \param gpio The GPIO pin to output the clock to. Valid GPIOs are: 21, 23, 24, 25. These GPIOs are connected to the GPOUT0-3 clock generators.
+ * \if rp2040_specific
+ * On RP2040 valid GPIOs are 21, 23, 24, 25.
+ * These GPIOs are connected to the GPOUT0-3 clock generators.
+ * \endif
+ * \if rp2350_specific
+ * On RP2350 valid GPIOs are 13, 15, 21, 23, 24, 25.
+ * GPIOs 13 and 21 are connected to the GPOUT0 clock generator.
+ * GPIOs 15 and 23 are connected to the GPOUT1 clock generator.
+ * GPIOs 24 and 25 are connected to the GPOUT2-3 clock generators.
+ * \endif
+ *
+ * \param gpio The GPIO pin to output the clock to.
  * \param src  The source clock. See the register field CLOCKS_CLK_GPOUT0_CTRL_AUXSRC for a full list. The list is the same for each GPOUT clock generator.
  * \param div  The float amount to divide the source clock by. This is useful to not overwhelm the GPIO pin with a fast clock.
  */
diff --git a/src/rp2_common/hardware_powman/powman.c b/src/rp2_common/hardware_powman/powman.c
index 2f9b9c367..9867259fd 100644
--- a/src/rp2_common/hardware_powman/powman.c
+++ b/src/rp2_common/hardware_powman/powman.c
@@ -97,12 +97,25 @@ void powman_timer_set_1khz_tick_source_xosc_with_hz(uint32_t xosc_freq_hz) {
     }
 }
 
+#ifndef GPIO_TO_POWMAN_EXT_TIME_REF_SOURCE
+#define GPIO_TO_POWMAN_EXT_TIME_REF_SOURCE(gpio, default_ext_time_ref_source) \
+    ((gpio) == 12 ? 0 :                                 \
+        ((gpio) == 20 ? 1 :                             \
+            ((gpio) == 14 ? 2 :                         \
+                ((gpio) == 22 ? 3 :                     \
+                    (default_ext_time_ref_source)))))
+#endif
+
+static inline uint32_t gpio_to_powman_ext_time_ref_source(uint gpio, uint32_t default_ext_time_ref_source) {
+    return GPIO_TO_POWMAN_EXT_TIME_REF_SOURCE(gpio, ({invalid_params_if(HARDWARE_POWMAN, true); default_ext_time_ref_source;}));
+}
+
 static void powman_timer_use_gpio(uint32_t gpio, uint32_t use, uint32_t using) {
     bool was_running = powman_timer_is_running();
     if (was_running) powman_timer_stop();
-    invalid_params_if(HARDWARE_POWMAN, !((gpio == 12) || (gpio == 14) || (gpio == 20) || (gpio == 22)));
+    uint32_t source = gpio_to_powman_ext_time_ref_source(gpio, 0);
     gpio_set_input_enabled(gpio, true);
-    powman_write(&powman_hw->ext_time_ref, gpio);
+    powman_write(&powman_hw->ext_time_ref, source);
     powman_set_bits(&powman_hw->timer, use);
     if (was_running) {
         powman_timer_start();