diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index 553f66414..75fb584c7 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -1201,8 +1201,8 @@ static void PacketReceived(PacketCommandNG *packet) {
 
             for (size_t i = 0; i < numofbytes; i += USB_CMD_DATA_SIZE) {
                 size_t len = MIN((numofbytes - i), USB_CMD_DATA_SIZE);
-                int16_t result = reply_old(CMD_DOWNLOADED_RAW_ADC_SAMPLES_125K, i, len, BigBuf_get_traceLen(), mem + startidx + i, len);
-                if (result <= 0)
+                int result = reply_old(CMD_DOWNLOADED_RAW_ADC_SAMPLES_125K, i, len, BigBuf_get_traceLen(), mem + startidx + i, len);
+                if (result != PM3_SUCCESS)
                     Dbprintf("transfer to client failed ::  | bytes between %d - %d (%d) | result: %d", i, i + len, len, result);
             }
             // Trigger a finish downloading signal with an ACK frame
@@ -1245,8 +1245,8 @@ static void PacketReceived(PacketCommandNG *packet) {
 
             for (size_t i = 0; i < numofbytes; i += USB_CMD_DATA_SIZE) {
                 len = MIN((numofbytes - i), USB_CMD_DATA_SIZE);
-                int16_t result = reply_old(CMD_DOWNLOADED_EML_BIGBUF, i, len, 0, mem + startidx + i, len);
-                if (result <= 0)
+                int result = reply_old(CMD_DOWNLOADED_EML_BIGBUF, i, len, 0, mem + startidx + i, len);
+                if (result != PM3_SUCCESS)
                     Dbprintf("transfer to client failed ::  | bytes between %d - %d (%d) | result: %d", i, i + len, len, result);
             }
             // Trigger a finish downloading signal with an ACK frame
@@ -1570,7 +1570,7 @@ void  __attribute__((noreturn)) AppMain(void) {
 
         // Check if there is a packet available
         PacketCommandNG rx;
-        int16_t ret = receive_ng(&rx);
+        int ret = receive_ng(&rx);
         if (ret == PM3_SUCCESS) {
             PacketReceived(&rx);
         } else if (ret != PM3_ENODATA) {
diff --git a/armsrc/apps.h b/armsrc/apps.h
index 723e55fa5..eef64e6fe 100644
--- a/armsrc/apps.h
+++ b/armsrc/apps.h
@@ -222,10 +222,10 @@ void iClass_Clone(uint8_t startblock, uint8_t endblock, uint8_t *data);
 void iClass_ReadCheck(uint8_t blockno, uint8_t keytype);
 
 // cmd.h
-int32_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
-int32_t reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
-int32_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len);
-int16_t receive_ng(PacketCommandNG *rx);
+int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+int reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len);
+int receive_ng(PacketCommandNG *rx);
 
 // util.h
 void HfSniff(int, int);
diff --git a/common/cmd.c b/common/cmd.c
index dfde60848..2605c40e8 100644
--- a/common/cmd.c
+++ b/common/cmd.c
@@ -47,7 +47,7 @@ extern void Dbprintf(const char *fmt, ...);
         reply_via_fpc = tmp;}
 #endif
 
-int32_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
+int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
     PacketResponseOLD txcmd;
 
     for (size_t i = 0; i < sizeof(PacketResponseOLD); i++)
@@ -67,24 +67,24 @@ int32_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, voi
         }
     }
 
-    int32_t sendlen = 0;
+    int result = PM3_EUNDEF;
     // Send frame and make sure all bytes are transmitted
 
     if (reply_via_fpc) {
 #ifdef WITH_FPC_HOST
-        sendlen = usart_writebuffer_sync((uint8_t *)&txcmd, sizeof(PacketResponseOLD));
+        result = usart_writebuffer_sync((uint8_t *)&txcmd, sizeof(PacketResponseOLD));
 //        Dbprintf_usb("Sent %i bytes over usart", len);
 #else
         return PM3_EDEVNOTSUPP;
 #endif
     } else {
-        sendlen = usb_write((uint8_t *)&txcmd, sizeof(PacketResponseOLD));
+        result = usb_write((uint8_t *)&txcmd, sizeof(PacketResponseOLD));
     }
 
-    return sendlen;
+    return result;
 }
 
-static int32_t reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, size_t len, bool ng) {
+static int reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, size_t len, bool ng) {
     PacketResponseNGRaw txBufferNG;
     size_t txBufferNGLen;
 //    for (size_t i = 0; i < sizeof(txBufferNG); i++)
@@ -119,28 +119,28 @@ static int32_t reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, si
     }
     txBufferNGLen = sizeof(PacketResponseNGPreamble) + len + sizeof(PacketResponseNGPostamble);
 
-    int32_t sendlen = 0;
+    int result = PM3_EUNDEF;
     // Send frame and make sure all bytes are transmitted
 
     if (reply_via_fpc) {
 #ifdef WITH_FPC_HOST
-        sendlen = usart_writebuffer_sync((uint8_t *)&txBufferNG, txBufferNGLen);
+        result = usart_writebuffer_sync((uint8_t *)&txBufferNG, txBufferNGLen);
 //        Dbprintf_usb("Sent %i bytes over usart", len);
 #else
         return PM3_EDEVNOTSUPP;
 #endif
     } else {
-        sendlen = usb_write((uint8_t *)&txBufferNG, txBufferNGLen);
+        result = usb_write((uint8_t *)&txBufferNG, txBufferNGLen);
     }
 
-    return sendlen;
+    return result;
 }
 
-int32_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len) {
+int reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len) {
     return reply_ng_internal(cmd, status, data, len, true);
 }
 
-int32_t reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
+int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
     uint16_t status = PM3_SUCCESS;
     uint64_t arg[3] = {arg0, arg1, arg2};
     if (len > USB_CMD_DATA_SIZE - sizeof(arg)) {
@@ -154,7 +154,7 @@ int32_t reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, voi
     return reply_ng_internal(cmd, status, cmddata, len + sizeof(arg), false);
 }
 
-static int16_t receive_ng_internal(PacketCommandNG *rx, uint32_t read_ng(uint8_t *data, size_t len), bool fpc) {
+static int receive_ng_internal(PacketCommandNG *rx, uint32_t read_ng(uint8_t *data, size_t len), bool fpc) {
     PacketCommandNGRaw rx_raw;
     size_t bytes = read_ng((uint8_t *)&rx_raw.pre, sizeof(PacketCommandNGPreamble));
     if (bytes == 0)
@@ -219,7 +219,7 @@ static int16_t receive_ng_internal(PacketCommandNG *rx, uint32_t read_ng(uint8_t
     return PM3_SUCCESS;
 }
 
-int16_t receive_ng(PacketCommandNG *rx) {
+int receive_ng(PacketCommandNG *rx) {
 
     // Check if there is a packet available
     if (usb_poll_validate_length())
diff --git a/common/cmd.h b/common/cmd.h
index e6e30aadc..fd42607f9 100644
--- a/common/cmd.h
+++ b/common/cmd.h
@@ -39,10 +39,10 @@
 #include "usart.h"
 #include "proxmark3.h"
 
-int32_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
-int32_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len);
-int32_t reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
-int16_t receive_ng(PacketCommandNG *rx);
+int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+int reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len);
+int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+int receive_ng(PacketCommandNG *rx);
 
 // Flags to tell where to add CRC on sent replies
 extern bool reply_with_crc_on_usb;
diff --git a/common/usart.c b/common/usart.c
index 8294844a2..f62ea1d21 100644
--- a/common/usart.c
+++ b/common/usart.c
@@ -129,7 +129,7 @@ uint32_t usart_read_ng(uint8_t *data, size_t len) {
 }
 
 // transfer from device to client
-inline int32_t usart_writebuffer_sync(uint8_t *data, size_t len) {
+inline int usart_writebuffer_sync(uint8_t *data, size_t len) {
 
     // Wait for current PDC bank to be free
     // (and check next bank too, in case there will be a usart_writebuffer_async)
@@ -139,7 +139,7 @@ inline int32_t usart_writebuffer_sync(uint8_t *data, size_t len) {
     // Wait until finishing all transfers to make sure "data" buffer can be discarded
     // (if we don't wait here, bulk send as e.g. "hw status" will fail)
     while (pUS1->US_TNCR || pUS1->US_TCR) {};
-    return len;
+    return PM3_SUCCESS;
 }
 
 void usart_init(void) {
diff --git a/common/usart.h b/common/usart.h
index ff65049fa..c6581526b 100644
--- a/common/usart.h
+++ b/common/usart.h
@@ -12,7 +12,7 @@
 void usart_init(void);
 void usart_close(void);
 
-int32_t usart_writebuffer_sync(uint8_t *data, size_t len);
+int usart_writebuffer_sync(uint8_t *data, size_t len);
 uint32_t usart_read_ng(uint8_t *data, size_t len);
 uint16_t usart_rxdata_available(void);
 #define USART_BUFFLEN 512
diff --git a/common/usb_cdc.c b/common/usb_cdc.c
index b464beffc..04f86ad71 100644
--- a/common/usb_cdc.c
+++ b/common/usb_cdc.c
@@ -709,7 +709,7 @@ uint32_t usb_read_ng(uint8_t *data, size_t len) {
 //* \fn    usb_write
 //* \brief Send through endpoint 2 (device to host)
 //*----------------------------------------------------------------------------
-int32_t usb_write(const uint8_t *data, const size_t len) {
+int usb_write(const uint8_t *data, const size_t len) {
 
     if (!len) return PM3_EINVARG;
     if (!usb_check()) return PM3_EIO;
@@ -758,7 +758,7 @@ int32_t usb_write(const uint8_t *data, const size_t len) {
     UDP_CLEAR_EP_FLAGS(AT91C_EP_IN, AT91C_UDP_TXCOMP);
     while (pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP) {};
 
-    return len;
+    return PM3_SUCCESS;
 }
 
 //*----------------------------------------------------------------------------
diff --git a/common/usb_cdc.h b/common/usb_cdc.h
index 3079f93e3..3dbe9df5f 100644
--- a/common/usb_cdc.h
+++ b/common/usb_cdc.h
@@ -47,7 +47,7 @@ bool usb_check(void);
 bool usb_poll(void);
 bool usb_poll_validate_length(void);
 uint32_t usb_read(uint8_t *data, size_t len);
-int32_t usb_write(const uint8_t *data, const size_t len);
+int usb_write(const uint8_t *data, const size_t len);
 uint32_t usb_read_ng(uint8_t *data, size_t len);
 
 void SetUSBreconnect(int value);