diff --git a/lib/usb_cdcacm.c b/lib/usb_cdcacm.c
index b3751ee..65fa9e9 100644
--- a/lib/usb_cdcacm.c
+++ b/lib/usb_cdcacm.c
@@ -168,7 +168,7 @@ static const struct usb_config_descriptor config = {
 	.bNumInterfaces = 2, // the number of interfaces in this configuration 
 	.bConfigurationValue = 1, // the index of this configuration
 	.iConfiguration = 0, // a string index describing this configuration (zero means not provided)
-	.bmAttributes = 0x80, // self powered (0<<6), supports remote wakeup (5<<0)
+	.bmAttributes = 0x80, // self powered (0<<6), supports remote wakeup (0<<5)
 	.bMaxPower = 0x32, // the maximum amount of current that this device will draw in 2mA units
 	// end of header
 	.interface = interfaces, // pointer to an array of interfaces
@@ -264,12 +264,16 @@ static void cdcacm_data_tx_cb(usbd_device *usbd_dev, uint8_t ep)
 	
 	/* transmit data */
 	if (tx_used) { // copy received data
-		for (usb_length=0; usb_length<sizeof(usb_data) && tx_used; usb_length++) { // only until buffer is full
-			usb_data[usb_length] = tx_buffer[tx_i]; // put data in transmit data
-			tx_i = (tx_i+1)%sizeof(rx_buffer); // update location on buffer
-			tx_used--; // update used size
+		for (usb_length=0; usb_length<sizeof(usb_data) && usb_length<tx_used; usb_length++) { // only until buffer is full
+			usb_data[usb_length] = tx_buffer[(tx_i+usb_length)%sizeof(tx_buffer)]; // put data in transmit data
 		}
-		while(usbd_ep_write_packet(usb_device, 0x82, usb_data, usb_length)==0);
+		// this could lead to a lock down
+		// while(usbd_ep_write_packet(usb_device, 0x82, usb_data, usb_length)==0);
+		// this is less critical
+		uint8_t transmitted = usbd_ep_write_packet(usb_device, 0x82, usb_data, usb_length); // try to transmit data
+		tx_i = (tx_i+transmitted)%sizeof(rx_buffer); // update location on buffer
+		tx_used -= transmitted; // update used size
+		
 	}
 }
 
@@ -328,9 +332,12 @@ char cdcacm_getchar(void)
 /* put character on USB CDC ACM (blocking) */
 void cdcacm_putchar(char c)
 {
-	if (tx_used<sizeof(tx_buffer)) {
+	if (tx_used<sizeof(tx_buffer)) { // buffer not full
 		tx_buffer[(tx_i+tx_used)%sizeof(tx_buffer)] = c; // put character in buffer
 		tx_used++; // update used buffer
+	} else { // buffer full
+		tx_i = (tx_i+1)%sizeof(tx_buffer); // shift start
+		tx_buffer[(tx_i+tx_used)%sizeof(tx_buffer)] = c; // overwrite old data
 	}
 	usbd_ep_write_packet(usb_device, 0x82, NULL, 0); // trigger tx (not sure why cdcacm_data_tx_cb doesn't work else)
 }