diff --git a/port/stm32-f4discovery-cc256x/port/port.c b/port/stm32-f4discovery-cc256x/port/port.c
index 5eabe061c..2346d913b 100644
--- a/port/stm32-f4discovery-cc256x/port/port.c
+++ b/port/stm32-f4discovery-cc256x/port/port.c
@@ -218,9 +218,7 @@ void hal_uart_dma_receive_block(uint8_t *data, uint16_t size){
  * @param len
  * @return
  */
-#include <stdio.h>
-#include <unistd.h>
-#include <errno.h>
+
 ssize_t _write(int file, const void *buf, size_t len);
 ssize_t _write(int file, const void *buf, size_t len){
 #if 1
diff --git a/port/stm32-f4discovery-usb/port/port.c b/port/stm32-f4discovery-usb/port/port.c
index 4511177bc..4da17a6da 100644
--- a/port/stm32-f4discovery-usb/port/port.c
+++ b/port/stm32-f4discovery-usb/port/port.c
@@ -37,6 +37,10 @@
 
 #define BTSTACK_FILE__ "port.c"
 
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+
 // include STM32 first to avoid warning about redefinition of UNUSED
 #include "stm32f4xx_hal.h"
 #include "main.h"
@@ -104,6 +108,43 @@ void hal_cpu_enable_irqs_and_sleep(void){
 
 int btstack_main(int argc, char ** argv);
 
+ssize_t _read(int fd, void * buf, size_t count){
+    UNUSED(fd);
+    UNUSED(buf);
+    UNUSED(count);
+    return -1;
+}
+
+int _close(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _isatty(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _lseek(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _fstat(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _kill (pid_t pid, int sig) {
+    UNUSED(pid);
+    UNUSED(sig);
+    return -1;
+}
+
+pid_t _getpid (void) {
+    return 0;
+}
+
 // main.c
 static void packet_handler (uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
     UNUSED(size);
diff --git a/port/stm32-l451-miromico-sx1280/port/btstack_port.c b/port/stm32-l451-miromico-sx1280/port/btstack_port.c
index b90653636..f6122f101 100644
--- a/port/stm32-l451-miromico-sx1280/port/btstack_port.c
+++ b/port/stm32-l451-miromico-sx1280/port/btstack_port.c
@@ -39,7 +39,10 @@
 
 #define DEBUG
 
+#include <stdio.h>
 #include <string.h>
+#include <unistd.h>
+#include <signal.h>
 
 // to get cpu intrinsics, .e.g __dissble_irq(), before BTstack includes to avoid re-defining UNUSED
 #include "stm32l4xx.h"
@@ -65,6 +68,43 @@
 #include "hci_dump_embedded_stdout.h"
 #endif
 
+ssize_t _read(int fd, void * buf, size_t count){
+    UNUSED(fd);
+    UNUSED(buf);
+    UNUSED(count);
+    return -1;
+}
+
+int _close(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _isatty(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _lseek(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _fstat(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _kill (pid_t pid, int sig) {
+    UNUSED(pid);
+    UNUSED(sig);
+    return -1;
+}
+
+pid_t _getpid (void) {
+    return 0;
+}
+
 void btstack_assert_failed(const char * file, uint16_t line_nr){
     printf("Assert: file %s, line %u\n", file, line_nr);
     while (1);
diff --git a/port/stm32-l476rg-nucleo-sx1280/port/btstack_port.c b/port/stm32-l476rg-nucleo-sx1280/port/btstack_port.c
index b90653636..f6122f101 100644
--- a/port/stm32-l476rg-nucleo-sx1280/port/btstack_port.c
+++ b/port/stm32-l476rg-nucleo-sx1280/port/btstack_port.c
@@ -39,7 +39,10 @@
 
 #define DEBUG
 
+#include <stdio.h>
 #include <string.h>
+#include <unistd.h>
+#include <signal.h>
 
 // to get cpu intrinsics, .e.g __dissble_irq(), before BTstack includes to avoid re-defining UNUSED
 #include "stm32l4xx.h"
@@ -65,6 +68,43 @@
 #include "hci_dump_embedded_stdout.h"
 #endif
 
+ssize_t _read(int fd, void * buf, size_t count){
+    UNUSED(fd);
+    UNUSED(buf);
+    UNUSED(count);
+    return -1;
+}
+
+int _close(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _isatty(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _lseek(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _fstat(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _kill (pid_t pid, int sig) {
+    UNUSED(pid);
+    UNUSED(sig);
+    return -1;
+}
+
+pid_t _getpid (void) {
+    return 0;
+}
+
 void btstack_assert_failed(const char * file, uint16_t line_nr){
     printf("Assert: file %s, line %u\n", file, line_nr);
     while (1);
diff --git a/port/stm32-wb55xx-nucleo-freertos/port/btstack_port.c b/port/stm32-wb55xx-nucleo-freertos/port/btstack_port.c
index aa29f7bfa..c2ad94331 100644
--- a/port/stm32-wb55xx-nucleo-freertos/port/btstack_port.c
+++ b/port/stm32-wb55xx-nucleo-freertos/port/btstack_port.c
@@ -45,6 +45,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
+#include <signal.h>
 
 #include "btstack_config.h"
 #include "main.h"
@@ -61,11 +63,12 @@
  *******************************************/
 extern UART_HandleTypeDef hTuart;
 
-int _write(int file, char* ptr, int len)
+ssize_t _write(int fd, const void* buf, size_t count)
 {
+    const uint8_t *ptr = buf;
     // expand '/n' to '/r/n'
     int pos;
-    for (pos=0;pos<len;pos++){
+    for (pos=0;pos<count;pos++){
         uint8_t next_char = *ptr++;
         if (next_char == '\n'){
             const uint8_t NEWLINE[] = "\r\n";
@@ -75,17 +78,61 @@ int _write(int file, char* ptr, int len)
         }
     }
 
-    return len;
+    return count;
 }
 
-int _read(int file, char* ptr, int len)
+ssize_t _read(int file, void * buf, size_t count)
 {
-    HAL_UART_Receive(&hTuart, (uint8_t*)ptr, len, 1000);
+    uint8_t *ptr = buf;
+    HAL_UART_Receive(&hTuart, ptr, count, 1000);
+    return count;
+}
+#else
+ssize_t _write(int fd, const void* buf, size_t count){
+    UNUSED(fd);
+    UNUSED(buf);
+    UNUSED(count);
+    return -1
+}
 
-    return len;
+ssize_t _read(int fd, void* buf, size_t count){
+    UNUSED(fd);
+    UNUSED(buf);
+    UNUSED(count);
+    return -1;
 }
 #endif
 
+int _close(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _isatty(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _lseek(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _fstat(int file){
+    UNUSED(file);
+    return -1;
+}
+
+int _kill (pid_t pid, int sig) {
+    UNUSED(pid);
+    UNUSED(sig);
+    return -1;
+}
+
+pid_t _getpid (void) {
+    return 0;
+}
+
 /********************************************
  *      hal_time_ms.h implementation
  *******************************************/