diff --git a/lib/usb_cdcacm.c b/lib/usb_cdcacm.c
index 27f3859..43f9059 100644
--- a/lib/usb_cdcacm.c
+++ b/lib/usb_cdcacm.c
@@ -181,6 +181,9 @@ static usbd_device *usb_device;
 static uint8_t rx_buffer[CDCACM_BUFFER] = {0};
 static volatile uint8_t rx_i = 0;
 static volatile uint8_t rx_used = 0;
+static uint8_t tx_buffer[CDCACM_BUFFER] = {0};
+static volatile uint8_t tx_i = 0;
+static volatile uint8_t tx_used = 0;
 /* show the user how much data received over USB is ready */
 volatile uint8_t cdcacm_received = 0; // same as rx_used, but since the user can write this variable we don't rely on it
 
@@ -191,30 +194,33 @@ static int cdcacm_control_request(usbd_device *usbd_dev, struct usb_setup_data *
 	(void)usbd_dev;
 
 	switch (req->bRequest) {
-	case USB_CDC_REQ_SET_CONTROL_LINE_STATE: {
-		/*
-		 * This Linux cdc_acm driver requires this to be implemented
-		 * even though it's optional in the CDC spec, and we don't
-		 * advertise it in the ACM functional descriptor.
-		 */
-		char local_buf[10];
-		struct usb_cdc_notification *notif = (void *)local_buf;
+		case USB_CDC_REQ_SET_CONTROL_LINE_STATE: {
+			/*
+			 * This Linux cdc_acm driver requires this to be implemented
+			 * even though it's optional in the CDC spec, and we don't
+			 * advertise it in the ACM functional descriptor.
+			 */
+			char local_buf[10];
+			struct usb_cdc_notification *notif = (void *)local_buf;
 
-		/* We echo signals back to host as notification. */
-		notif->bmRequestType = 0xA1;
-		notif->bNotification = USB_CDC_NOTIFY_SERIAL_STATE;
-		notif->wValue = 0;
-		notif->wIndex = 0;
-		notif->wLength = 2;
-		local_buf[8] = req->wValue & 3;
-		local_buf[9] = 0;
-		// usbd_ep_write_packet(0x83, buf, 10);
-		return 1;
+			/* We echo signals back to host as notification. */
+			notif->bmRequestType = 0xA1;
+			notif->bNotification = USB_CDC_NOTIFY_SERIAL_STATE;
+			notif->wValue = 0;
+			notif->wIndex = 0;
+			notif->wLength = 2;
+			local_buf[8] = req->wValue & 3;
+			local_buf[9] = 0;
+			usbd_ep_write_packet(usbd_dev, 0x83, local_buf, 10);
+			return 1;
 		}
-	case USB_CDC_REQ_SET_LINE_CODING:
-		if (*len < sizeof(struct usb_cdc_line_coding))
+		case USB_CDC_REQ_SET_LINE_CODING:
+			if (*len < sizeof(struct usb_cdc_line_coding)) {
+				return 0;
+			}
+			return 1;
+		default:
 			return 0;
-		return 1;
 	}
 	return 0;
 }
@@ -238,13 +244,32 @@ static void cdcacm_data_rx_cb(usbd_device *usbd_dev, uint8_t ep)
 	}
 }
 
+static void cdcacm_data_tx_cb(usbd_device *usbd_dev, uint8_t ep)
+{
+	(void)ep;
+	(void)usbd_dev;
+
+	char usb_data[64] = {0}; // buffer to send data
+	uint16_t usb_length = 0; // length of transmitted data
+	
+	/* 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
+		}
+		while(usbd_ep_write_packet(usb_device, 0x82, usb_data, usb_length)==0);
+	}
+}
+
 static void cdcacm_set_config(usbd_device *usbd_dev, uint16_t wValue)
 {
 	(void)wValue;
 	(void)usbd_dev;
 
 	usbd_ep_setup(usbd_dev, 0x01, USB_ENDPOINT_ATTR_BULK, 64, cdcacm_data_rx_cb);
-	usbd_ep_setup(usbd_dev, 0x82, USB_ENDPOINT_ATTR_BULK, 64, NULL);
+	usbd_ep_setup(usbd_dev, 0x82, USB_ENDPOINT_ATTR_BULK, 64, cdcacm_data_tx_cb);
 	usbd_ep_setup(usbd_dev, 0x83, USB_ENDPOINT_ATTR_INTERRUPT, 16, NULL);
 
 	usbd_register_control_callback( usbd_dev, USB_REQ_TYPE_CLASS | USB_REQ_TYPE_INTERFACE, USB_REQ_TYPE_TYPE | USB_REQ_TYPE_RECIPIENT, cdcacm_control_request);
@@ -272,13 +297,16 @@ void cdcacm_setup(void)
 	rx_i = 0;
 	rx_used = 0;
 	cdcacm_received = 0;
+	
+	/* start sending */
+	usbd_ep_write_packet(usb_device, 0x82, NULL, 0);
 }
 
 /* get character from USB CDC ACM (blocking) */
 char cdcacm_getchar(void)
 {
 	while (!rx_used) { // idle until data is available
-		__WFI(); // sleep until interrupt;
+		__WFI(); // sleep until interrupt (not sure if it's a good idea here
 	}
 	char to_return = rx_buffer[rx_i]; // get the next available character
 	rx_i = (rx_i+1)%sizeof(rx_buffer); // update used buffer
@@ -290,7 +318,11 @@ char cdcacm_getchar(void)
 /* put character on USB CDC ACM (blocking) */
 void cdcacm_putchar(char c)
 {
-	while(usbd_ep_write_packet(usb_device, 0x82, &c, 1)==0); // sending single characters at a time isn't very optimal, but I didn't find a way to do it USB request based
+	if (tx_used<sizeof(tx_buffer)) {
+		tx_buffer[(tx_i+tx_used)%sizeof(tx_buffer)] = c; // put character in buffer
+		tx_used++; // update used buffer
+	}
+	usbd_ep_write_packet(usb_device, 0x82, NULL, 0); // trigger tx (not sure why cdcacm_data_tx_cb doesn't work else)
 }
 
 void usb_wakeup_isr(void) {