diff --git a/examples/stm32/f1/lisa-m/usb_cdcacm/cdcacm.c b/examples/stm32/f1/lisa-m/usb_cdcacm/cdcacm.c
index 74823283..7108263d 100644
--- a/examples/stm32/f1/lisa-m/usb_cdcacm/cdcacm.c
+++ b/examples/stm32/f1/lisa-m/usb_cdcacm/cdcacm.c
@@ -200,10 +200,10 @@ static void cdcacm_data_rx_cb(u8 ep)
 {
 	(void)ep;
 
-	char buf[128];
-	int len = usbd_ep_read_packet(0x01, buf, 128);
+	char buf[64];
+	int len = usbd_ep_read_packet(0x01, buf, 64);
 	if(len) { 
-		usbd_ep_write_packet(0x82, buf, len);
+		while(usbd_ep_write_packet(0x82, buf, len) == 0);
 		buf[len] = 0;
 	}