diff --git a/src/platform/esp32/main-esp32.cpp b/src/platform/esp32/main-esp32.cpp
index 7b6b9dcff..f47f0e1bb 100644
--- a/src/platform/esp32/main-esp32.cpp
+++ b/src/platform/esp32/main-esp32.cpp
@@ -22,6 +22,7 @@
 #include "target_specific.h"
 #include <Preferences.h>
 #include <driver/rtc_io.h>
+#include <driver/uart.h>
 #include <nvs.h>
 #include <nvs_flash.h>
 
@@ -263,3 +264,51 @@ void cpuDeepSleep(uint32_t msecToWake)
     esp_sleep_enable_timer_wakeup(msecToWake * 1000ULL); // call expects usecs
     esp_deep_sleep_start();                              // TBD mA sleep current (battery)
 }
+
+bool setSerialClockToRefTick(int uart_num)
+{
+#if !SOC_UART_SUPPORT_REF_TICK
+    return false;
+#else
+    uart_config_t uart_config;
+    uint32_t baudrate;
+
+    if (uart_get_baudrate(uart_num, &baudrate) != ESP_OK) {
+        LOG_ERROR("Unable to get UART baudrate");
+        return false;
+    }
+
+    uart_config.baud_rate = (int)baudrate;
+
+    if (uart_get_word_length(uart_num, &uart_config.data_bits) != ESP_OK) {
+        LOG_ERROR("Unable to get UART baudrate");
+        return false;
+    }
+    if (uart_get_parity(uart_num, &uart_config.parity) != ESP_OK) {
+        LOG_ERROR("Unable to get UART baudrate");
+        return false;
+    }
+    if (uart_get_stop_bits(uart_num, &uart_config.stop_bits) != ESP_OK) {
+        LOG_ERROR("Unable to get UART baudrate");
+        return false;
+    }
+    if (uart_get_hw_flow_ctrl(uart_num, &uart_config.flow_ctrl) != ESP_OK) {
+        LOG_ERROR("Unable to get UART baudrate");
+        return false;
+    }
+
+    if (uart_config.flow_ctrl != UART_HW_FLOWCTRL_DISABLE) {
+        uart_config.rx_flow_ctrl_thresh = 122;
+    }
+
+    uart_config.source_clk = UART_SCLK_REF_TICK;
+
+    // Configure UART parameters
+    if (uart_param_config(uart_num, &uart_config) != ESP_OK) {
+        LOG_ERROR("Unable to get UART baudrate");
+        return false;
+    }
+
+    return true;
+#endif
+}
diff --git a/src/sleep.cpp b/src/sleep.cpp
index 7cfcece8a..70d431798 100644
--- a/src/sleep.cpp
+++ b/src/sleep.cpp
@@ -58,6 +58,9 @@ Observable<esp_sleep_wakeup_cause_t> notifyLightSleepEnd;
 esp_pm_lock_handle_t pmLightSleepLock;
 #endif
 
+// this are imported symbol with target-specific implementation
+bool setSerialClockToRefTick(int uart_num);
+
 // restores GPIO function after sleep
 void gpioReset(void);
 // enables button wake-up interrupt
@@ -68,6 +71,9 @@ void enableLoraInterrupt(void);
 bool shouldLoraWake(uint32_t msecToWake);
 #endif
 
+// this are imported symbol with target-specific implementation
+void cpuDeepSleep(uint32_t msecToWake);
+
 // deep sleep support
 RTC_DATA_ATTR int bootCount = 0;
 
@@ -427,6 +433,13 @@ void doLightSleep(uint32_t sleepMsec)
 void initLightSleep()
 {
     esp_err_t res;
+    bool dfsSupported = true;
+
+#if defined(CONFIG_IDF_TARGET_ESP32) || defined(CONFIG_IDF_TARGET_ESP32S2)
+    if (dfsSupported) {
+        dfsSupported &= setSerialClockToRefTick(UART_NUM_0);
+    }
+#endif
 
 #ifdef HAS_ESP32_PM_SUPPORT
     res = esp_pm_lock_create(ESP_PM_NO_LIGHT_SLEEP, 0, "meshtastic", &pmLightSleepLock);
@@ -437,7 +450,7 @@ void initLightSleep()
 
     esp_pm_config_esp32_t pm_config;
     pm_config.max_freq_mhz = 80;
-    pm_config.min_freq_mhz = 20;
+    pm_config.min_freq_mhz = dfsSupported ? 20 : pm_config.max_freq_mhz;
 #ifdef HAS_ESP32_DYNAMIC_LIGHT_SLEEP
     pm_config.light_sleep_enable = true;
 #else
diff --git a/src/sleep.h b/src/sleep.h
index 14ac890b2..ea2906c44 100644
--- a/src/sleep.h
+++ b/src/sleep.h
@@ -21,7 +21,7 @@ void doLightSleep(uint32_t msecToWake);
 
 // perform power on init that we do on each wake from deep sleep
 void initDeepSleep();
-void doDeepSleep(uint32_t msecToWake, bool skipPreflight, bool skipSaveNodeDb), cpuDeepSleep(uint32_t msecToWake);
+void doDeepSleep(uint32_t msecToWake, bool skipPreflight, bool skipSaveNodeDb);
 
 void setCPUFast(bool on);
 
diff --git a/variants/esp32/heltec_v2.1/platformio.ini b/variants/esp32/heltec_v2.1/platformio.ini
index 763f9764c..74d991ce7 100644
--- a/variants/esp32/heltec_v2.1/platformio.ini
+++ b/variants/esp32/heltec_v2.1/platformio.ini
@@ -1,9 +1,11 @@
 [env:heltec-v2_1]
 board_level = extra
-;build_type = debug ; to make it possible to step through our jtag debugger 
+;build_type = debug ; to make it possible to step through our jtag debugger
 extends = esp32_base
 board = heltec_wifi_lora_32_V2
-build_flags = 
+platform_packages =
+    platformio/framework-arduinoespressif32 @ https://github.com/m1nl/arduino-esp32/archive/refs/tags/2.0.17+7b9546f7.tar.gz ; optimize IRAM usage for ESP32 platform
+build_flags =
   ${esp32_base.build_flags}
   -D HELTEC_V2_1
   -I variants/esp32/heltec_v2.1