diff --git a/src/helper/binarybuffer.c b/src/helper/binarybuffer.c
index c1e632265..26aa8cced 100644
--- a/src/helper/binarybuffer.c
+++ b/src/helper/binarybuffer.c
@@ -369,17 +369,42 @@ void bit_copy_discard(struct bit_copy_queue *q)
 	}
 }
 
-int unhexify(char *bin, const char *hex, int count)
+/**
+ * Convert a string of hexadecimal pairs into its binary
+ * representation.
+ *
+ * @param[out] bin Buffer to store binary representation. The buffer size must
+ *                 be at least @p count.
+ * @param[in] hex String with hexadecimal pairs to convert into its binary
+ *                representation.
+ * @param[in] count Number of hexadecimal pairs to convert.
+ *
+ * @return The number of converted hexadecimal pairs.
+ */
+size_t unhexify(uint8_t *bin, const char *hex, size_t count)
 {
-	int i, tmp;
+	size_t i;
+	char tmp;
 
-	for (i = 0; i < count; i++) {
-		if (sscanf(hex + (2 * i), "%02x", &tmp) != 1)
-			return i;
-		bin[i] = tmp;
+	if (!bin || !hex)
+		return 0;
+
+	memset(bin, 0, count);
+
+	for (i = 0; i < 2 * count; i++) {
+		if (hex[i] >= 'a' && hex[i] <= 'f')
+			tmp = hex[i] - 'a' + 10;
+		else if (hex[i] >= 'A' && hex[i] <= 'F')
+			tmp = hex[i] - 'A' + 10;
+		else if (hex[i] >= '0' && hex[i] <= '9')
+			tmp = hex[i] - '0';
+		else
+			return i / 2;
+
+		bin[i / 2] |= tmp << (4 * ((i + 1) % 2));
 	}
 
-	return i;
+	return i / 2;
 }
 
 int hexify(char *hex, const char *bin, int count, int out_maxlen)
diff --git a/src/helper/binarybuffer.h b/src/helper/binarybuffer.h
index dd0d275ab..b035779af 100644
--- a/src/helper/binarybuffer.h
+++ b/src/helper/binarybuffer.h
@@ -234,7 +234,7 @@ void bit_copy_discard(struct bit_copy_queue *q);
 
 /* functions to convert to/from hex encoded buffer
  * used in ti-icdi driver and gdb server */
-int unhexify(char *bin, const char *hex, int count);
+size_t unhexify(uint8_t *bin, const char *hex, size_t count);
 int hexify(char *hex, const char *bin, int count, int out_maxlen);
 void buffer_shr(void *_buf, unsigned buf_len, unsigned count);
 
diff --git a/src/jtag/drivers/ti_icdi_usb.c b/src/jtag/drivers/ti_icdi_usb.c
index 3db03b032..7a6272fdb 100644
--- a/src/jtag/drivers/ti_icdi_usb.c
+++ b/src/jtag/drivers/ti_icdi_usb.c
@@ -266,7 +266,7 @@ static int icdi_get_cmd_result(void *handle)
 
 	if (h->read_buffer[offset] == 'E') {
 		/* get error code */
-		char result;
+		uint8_t result;
 		if (unhexify(&result, h->read_buffer + offset + 1, 1) != 1)
 			return ERROR_FAIL;
 		return result;
@@ -328,7 +328,7 @@ static int icdi_usb_version(void *handle)
 	}
 
 	/* convert reply */
-	if (unhexify(version, h->read_buffer + 2, 4) != 4) {
+	if (unhexify((uint8_t *)version, h->read_buffer + 2, 4) != 4) {
 		LOG_WARNING("unable to get ICDI version");
 		return ERROR_OK;
 	}
@@ -495,7 +495,7 @@ static int icdi_usb_read_reg(void *handle, int num, uint32_t *val)
 
 	/* convert result */
 	uint8_t buf[4];
-	if (unhexify((char *)buf, h->read_buffer + 2, 4) != 4) {
+	if (unhexify(buf, h->read_buffer + 2, 4) != 4) {
 		LOG_ERROR("failed to convert result");
 		return ERROR_FAIL;
 	}
diff --git a/src/rtos/rtos.c b/src/rtos/rtos.c
index 4c99ad233..448c49c06 100644
--- a/src/rtos/rtos.c
+++ b/src/rtos/rtos.c
@@ -213,7 +213,7 @@ int rtos_qsymbol(struct connection *connection, char const *packet, int packet_s
 		goto done;
 
 	/* Decode any symbol name in the packet*/
-	int len = unhexify(cur_sym, strchr(packet + 8, ':') + 1, strlen(strchr(packet + 8, ':') + 1));
+	size_t len = unhexify((uint8_t *)cur_sym, strchr(packet + 8, ':') + 1, strlen(strchr(packet + 8, ':') + 1));
 	cur_sym[len] = 0;
 
 	if ((strcmp(packet, "qSymbol::") != 0) &&               /* GDB is not offering symbol lookup for the first time */
diff --git a/src/server/gdb_server.c b/src/server/gdb_server.c
index d09a8be6e..f85fa1bde 100644
--- a/src/server/gdb_server.c
+++ b/src/server/gdb_server.c
@@ -1449,7 +1449,7 @@ static int gdb_write_memory_packet(struct connection *connection,
 
 	LOG_DEBUG("addr: 0x%8.8" PRIx32 ", len: 0x%8.8" PRIx32 "", addr, len);
 
-	if (unhexify((char *)buffer, separator, len) != (int)len)
+	if (unhexify(buffer, separator, len) != len)
 		LOG_ERROR("unable to decode memory packet");
 
 	retval = target_write_buffer(target, addr, len, buffer);
@@ -2277,7 +2277,7 @@ static int gdb_query_packet(struct connection *connection,
 		if (packet_size > 6) {
 			char *cmd;
 			cmd = malloc((packet_size - 6) / 2 + 1);
-			int len = unhexify(cmd, packet + 6, (packet_size - 6) / 2);
+			size_t len = unhexify((uint8_t *)cmd, packet + 6, (packet_size - 6) / 2);
 			cmd[len] = 0;
 
 			/* We want to print all debug output to GDB connection */