diff --git a/platform/embedded/btstack_uart_block_embedded.c b/platform/embedded/btstack_uart_block_embedded.c
index 63dcfc130..ca5590d1d 100644
--- a/platform/embedded/btstack_uart_block_embedded.c
+++ b/platform/embedded/btstack_uart_block_embedded.c
@@ -145,7 +145,9 @@ static const btstack_uart_block_t btstack_uart_embedded = {
     /* int  (*set_baudrate)(uint32_t baudrate); */                    &hal_uart_dma_set_baud,
     /* int  (*set_parity)(int parity); */                             &btstack_uart_embedded_set_parity,
     /* void (*receive_block)(uint8_t *buffer, uint16_t len); */       &btstack_uart_embedded_receive_block,
-    /* void (*send_block)(const uint8_t *buffer, uint16_t length); */ &btstack_uart_embedded_send_block    
+    /* void (*send_block)(const uint8_t *buffer, uint16_t length); */ &btstack_uart_embedded_send_block,    
+    /* int (*get_supported_sleep_modes); */                           NULL,
+    /* void (*set_sleep)(btstack_uart_sleep_mode_t sleep_mode); */    NULL
 };
 
 const btstack_uart_block_t * btstack_uart_block_embedded_instance(void){
diff --git a/platform/posix/btstack_uart_block_posix.c b/platform/posix/btstack_uart_block_posix.c
index 6697207ad..7608b9a9a 100644
--- a/platform/posix/btstack_uart_block_posix.c
+++ b/platform/posix/btstack_uart_block_posix.c
@@ -351,7 +351,9 @@ static const btstack_uart_block_t btstack_uart_posix = {
     /* int  (*set_baudrate)(uint32_t baudrate); */                    &btstack_uart_posix_set_baudrate,
     /* int  (*set_parity)(int parity); */                             &btstack_uart_posix_set_parity,
     /* void (*receive_block)(uint8_t *buffer, uint16_t len); */       &btstack_uart_posix_receive_block,
-    /* void (*send_block)(const uint8_t *buffer, uint16_t length); */ &btstack_uart_posix_send_block    
+    /* void (*send_block)(const uint8_t *buffer, uint16_t length); */ &btstack_uart_posix_send_block,
+    /* int (*get_supported_sleep_modes); */                           NULL,
+    /* void (*set_sleep)(btstack_uart_sleep_mode_t sleep_mode); */    NULL
 };
 
 const btstack_uart_block_t * btstack_uart_block_posix_instance(void){
diff --git a/src/btstack_uart_block.h b/src/btstack_uart_block.h
index 5cd834c7a..a7ea609f1 100644
--- a/src/btstack_uart_block.h
+++ b/src/btstack_uart_block.h
@@ -53,6 +53,21 @@ typedef struct {
     const char *device_name;
 } btstack_uart_config_t;
 
+typedef enum {
+    // UART active, sleep off
+    BTSTACK_UART_SLEEP_OFF = 0,
+    // used for eHCILL
+    BTSTACK_UART_SLEEP_RTS_HIGH_WAKE_ON_CTS_PULSE,
+    // used for H5 and for eHCILL without support for wake on CTS pulse
+    BTSTACK_UART_SLEEP_RTS_LOW_WAKE_ON_RX_EDGE, 
+
+} btstack_uart_sleep_mode_t;
+
+typedef enum { 
+    BTSTACK_UART_SLEEP_MASK_HIGH_WAKE_ON_CTS_PULSE  = 1 << BTSTACK_UART_SLEEP_RTS_HIGH_WAKE_ON_CTS_PULSE,
+    BTSTACK_UART_SLEEP_MASK_RTS_LOW_WAKE_ON_RX_EDGE = 1 << BTSTACK_UART_SLEEP_RTS_LOW_WAKE_ON_RX_EDGE
+} btstack_uart_sleep_mode_mask_t;
+
 typedef struct {
     /**
      * init transport
@@ -100,8 +115,22 @@ typedef struct {
      */
     void (*send_block)(const uint8_t *buffer, uint16_t length);
 
-    // void hal_uart_dma_set_sleep(uint8_t sleep);
-    // void hal_uart_dma_set_csr_irq_handler( void (*csr_irq_handler)(void));
+    // support for sleep modes in TI's H4 eHCILL and H5
+
+    /**
+     * query supported wakeup mechanisms
+     * @return supported_sleep_modes mask
+     */
+     int (*get_supported_sleep_modes);
+
+    /**
+     * set UART sleep mode - allows to turn off UART and it's clocks to save energy
+     * Supported sleep modes:
+     * - off: UART active, RTS low if receive_block was called and block not read yet
+     * - RTS high, wake on CTS: RTS should be high. On CTS pulse, UART gets enabled again and RTS goes to low
+     * - RTS low, wake on RX: data on RX will trigger UART enable, bytes might get lost
+     */
+    void (*set_sleep)(btstack_uart_sleep_mode_t sleep_mode);
 
 } btstack_uart_block_t;