diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index 89d462003..553f66414 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -1203,7 +1203,7 @@ static void PacketReceived(PacketCommandNG *packet) {
                 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)
-                    Dbprintf("transfer to client failed ::  | bytes between %d - %d (%d)", i, i + len, len);
+                    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
             // iceman,  when did sending samplingconfig array got attached here?!?
@@ -1247,7 +1247,7 @@ static void PacketReceived(PacketCommandNG *packet) {
                 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)
-                    Dbprintf("transfer to client failed ::  | bytes between %d - %d (%d)", i, i + len, len);
+                    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
             reply_old(CMD_ACK, 1, 0, 0, 0, 0);
diff --git a/armsrc/apps.h b/armsrc/apps.h
index 507c04782..723e55fa5 100644
--- a/armsrc/apps.h
+++ b/armsrc/apps.h
@@ -222,8 +222,9 @@ void iClass_Clone(uint8_t startblock, uint8_t endblock, uint8_t *data);
 void iClass_ReadCheck(uint8_t blockno, uint8_t keytype);
 
 // cmd.h
-int16_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
-int16_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len);
+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);
 
 // util.h
diff --git a/common/cmd.c b/common/cmd.c
index 13ca856d8..dfde60848 100644
--- a/common/cmd.c
+++ b/common/cmd.c
@@ -47,7 +47,7 @@ extern void Dbprintf(const char *fmt, ...);
         reply_via_fpc = tmp;}
 #endif
 
-int16_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
+int32_t 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++)
@@ -67,7 +67,7 @@ int16_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, voi
         }
     }
 
-    uint32_t sendlen = 0;
+    int32_t sendlen = 0;
     // Send frame and make sure all bytes are transmitted
 
     if (reply_via_fpc) {
@@ -84,7 +84,7 @@ int16_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, voi
     return sendlen;
 }
 
-static int16_t reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, size_t len, bool ng) {
+static int32_t 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++)
@@ -119,7 +119,7 @@ static int16_t reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, si
     }
     txBufferNGLen = sizeof(PacketResponseNGPreamble) + len + sizeof(PacketResponseNGPostamble);
 
-    uint32_t sendlen = 0;
+    int32_t sendlen = 0;
     // Send frame and make sure all bytes are transmitted
 
     if (reply_via_fpc) {
@@ -136,11 +136,11 @@ static int16_t reply_ng_internal(uint16_t cmd, int16_t status, uint8_t *data, si
     return sendlen;
 }
 
-int16_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len) {
+int32_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len) {
     return reply_ng_internal(cmd, status, data, len, true);
 }
 
-int16_t reply_mix(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) {
     uint16_t status = PM3_SUCCESS;
     uint64_t arg[3] = {arg0, arg1, arg2};
     if (len > USB_CMD_DATA_SIZE - sizeof(arg)) {
diff --git a/common/cmd.h b/common/cmd.h
index 4c9d6b1d1..e6e30aadc 100644
--- a/common/cmd.h
+++ b/common/cmd.h
@@ -39,9 +39,9 @@
 #include "usart.h"
 #include "proxmark3.h"
 
-int16_t reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
-int16_t reply_ng(uint16_t cmd, int16_t status, uint8_t *data, size_t len);
-int16_t reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+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);
 
 // Flags to tell where to add CRC on sent replies
diff --git a/common/usart.c b/common/usart.c
index cb4153062..8294844a2 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 int16_t usart_writebuffer_sync(uint8_t *data, size_t len) {
+inline int32_t 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)
diff --git a/common/usart.h b/common/usart.h
index 1b3c6ded7..ff65049fa 100644
--- a/common/usart.h
+++ b/common/usart.h
@@ -12,7 +12,7 @@
 void usart_init(void);
 void usart_close(void);
 
-int16_t usart_writebuffer_sync(uint8_t *data, size_t len);
+int32_t 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 9090d8dc2..b464beffc 100644
--- a/common/usb_cdc.c
+++ b/common/usb_cdc.c
@@ -709,13 +709,13 @@ uint32_t usb_read_ng(uint8_t *data, size_t len) {
 //* \fn    usb_write
 //* \brief Send through endpoint 2 (device to host)
 //*----------------------------------------------------------------------------
-uint32_t usb_write(const uint8_t *data, const size_t len) {
+int32_t usb_write(const uint8_t *data, const size_t len) {
 
-    if (!len) return 0;
-    if (!usb_check()) return 0;
+    if (!len) return PM3_EINVARG;
+    if (!usb_check()) return PM3_EIO;
 
     // can we write?
-    if ((pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXPKTRDY) != 0) return 0;
+    if ((pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXPKTRDY) != 0) return PM3_EIO;
 
     size_t length = len;
     uint32_t cpt = 0;
@@ -741,7 +741,7 @@ uint32_t usb_write(const uint8_t *data, const size_t len) {
         // Wait for previous chunk to be sent
         // (iceman) when is the bankswapping done?
         while (!(pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP)) {
-            if (!usb_check()) return length;
+            if (!usb_check()) return PM3_EIO;
         }
 
         UDP_CLEAR_EP_FLAGS(AT91C_EP_IN, AT91C_UDP_TXCOMP);
@@ -752,13 +752,13 @@ uint32_t usb_write(const uint8_t *data, const size_t len) {
 
     // Wait for the end of transfer
     while (!(pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP)) {
-        if (!usb_check()) return length;
+        if (!usb_check()) return PM3_EIO;
     }
 
     UDP_CLEAR_EP_FLAGS(AT91C_EP_IN, AT91C_UDP_TXCOMP);
     while (pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP) {};
 
-    return length;
+    return len;
 }
 
 //*----------------------------------------------------------------------------
diff --git a/common/usb_cdc.h b/common/usb_cdc.h
index d5a4451ea..3079f93e3 100644
--- a/common/usb_cdc.h
+++ b/common/usb_cdc.h
@@ -47,9 +47,8 @@ bool usb_check(void);
 bool usb_poll(void);
 bool usb_poll_validate_length(void);
 uint32_t usb_read(uint8_t *data, size_t len);
-uint32_t usb_write(const uint8_t *data, const size_t len);
+int32_t usb_write(const uint8_t *data, const size_t len);
 uint32_t usb_read_ng(uint8_t *data, size_t len);
-uint32_t usb_write_ng(const uint8_t *data, const size_t len);
 
 void SetUSBreconnect(int value);
 int GetUSBreconnect(void);