diff --git a/lib/pbio/drv/usb/usb.c b/lib/pbio/drv/usb/usb.c
index fda7e63fd..52b93417c 100644
--- a/lib/pbio/drv/usb/usb.c
+++ b/lib/pbio/drv/usb/usb.c
@@ -294,14 +294,14 @@ static pbio_error_t pbdrv_usb_process_thread(pbio_os_state_t *state, void *conte
                 pbdrv_usb_respond_soon = false;
 
                 // Send the response.
-                PBIO_OS_AWAIT(state, &sub, err = pbdrv_usb_tx_response(&sub, error_code));
+                PBIO_OS_AWAIT(state, &sub, err = pbdrv_usb_tx_response(&sub, error_code, pbdrv_usb_process.request == PBIO_OS_PROCESS_REQUEST_TYPE_CANCEL));
                 if (err != PBIO_SUCCESS) {
                     pbdrv_usb_reset_state();
                     PBIO_OS_AWAIT(state, &sub, pbdrv_usb_tx_reset(&sub));
                 }
             } else if (pbdrv_usb_connection_is_active() && update_and_get_event_buffer(&noti_buf, &noti_size)) {
                 // Send out pending event if any.
-                PBIO_OS_AWAIT(state, &sub, err = pbdrv_usb_tx_event(&sub, noti_buf, *noti_size));
+                PBIO_OS_AWAIT(state, &sub, err = pbdrv_usb_tx_event(&sub, noti_buf, *noti_size, pbdrv_usb_process.request == PBIO_OS_PROCESS_REQUEST_TYPE_CANCEL));
                 *noti_size = 0;
                 if (err != PBIO_SUCCESS) {
                     pbdrv_usb_reset_state();
diff --git a/lib/pbio/drv/usb/usb.h b/lib/pbio/drv/usb/usb.h
index 81a4863b5..1bf67a440 100644
--- a/lib/pbio/drv/usb/usb.h
+++ b/lib/pbio/drv/usb/usb.h
@@ -51,7 +51,7 @@ uint32_t pbdrv_usb_get_data_and_start_receive(uint8_t *data);
 /**
  * Sends and awaits event message from hub to host via the Pybricks USB interface OUT endpoint.
  *
- * Driver-specific implementation. Must return within ::PBDRV_USB_TRANSMIT_TIMEOUT.
+ * Driver-specific implementation. Must support being canceled via @p cancel.
  *
  * The USB process ensures that only one call is made at once.
  *
@@ -60,31 +60,33 @@ uint32_t pbdrv_usb_get_data_and_start_receive(uint8_t *data);
  * @param [in] state    Protothread state.
  * @param [in] data     Data to send.
  * @param [in] size     Data size.
+ * @param [in] cancel   If true, stop waiting for completion and return error.
  * @return              ::PBIO_SUCCESS on completion.
  *                      ::PBIO_ERROR_INVALID_OP if there is no connection.
  *                      ::PBIO_ERROR_AGAIN while awaiting.
  *                      ::PBIO_ERROR_BUSY if this operation is already ongoing.
  *                      ::PBIO_ERROR_INVALID_ARG if @p size is too large.
- *                      ::PBIO_ERROR_TIMEDOUT if the operation was started but could not complete.
+ *                      ::PBIO_ERROR_CANCELED if the operation was canceled.
  */
-pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size);
+pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size, bool cancel);
 
 /**
  * Sends and awaits response to an earlier incoming message.
  *
- * Driver-specific implementation. Must return within ::PBDRV_USB_TRANSMIT_TIMEOUT.
+ * Driver-specific implementation. Must support being canceled via @p cancel.
  *
  * The USB process ensures that only one call is made at once.
  *
  * @param [in] state    Protothread state.
  * @param [in] code     Error code to send.
+ * @param [in] cancel   If true, stop waiting for completion and return error.
  * @return              ::PBIO_SUCCESS on completion.
  *                      ::PBIO_ERROR_INVALID_OP if there is no connection.
  *                      ::PBIO_ERROR_AGAIN while awaiting.
  *                      ::PBIO_ERROR_BUSY if this operation is already ongoing.
- *                      ::PBIO_ERROR_TIMEDOUT if the operation was started but could not complete.
+ *                      ::PBIO_ERROR_CANCELED if the operation was canceled.
  */
-pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code);
+pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code, bool cancel);
 
 /**
  * Resets the driver transmission state.
diff --git a/lib/pbio/drv/usb/usb_ev3.c b/lib/pbio/drv/usb/usb_ev3.c
index 868c64531..85c7d8318 100644
--- a/lib/pbio/drv/usb/usb_ev3.c
+++ b/lib/pbio/drv/usb/usb_ev3.c
@@ -1023,9 +1023,7 @@ pbio_error_t pbdrv_usb_tx_reset(pbio_os_state_t *state) {
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size) {
-
-    static pbio_os_timer_t timer;
+pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size, bool cancel) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -1034,28 +1032,20 @@ pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uin
     }
 
     transmitting = true;
-    pbio_os_timer_set(&timer, PBDRV_USB_TRANSMIT_TIMEOUT);
 
     // Transmit event.
     pbdrv_cache_prepare_before_dma(data, size);
     usb_setup_tx_dma_desc(CPPI_DESC_TX_PYBRICKS_EVENT, (uint8_t *)data, size);
 
-    PBIO_OS_AWAIT_UNTIL(state, !transmitting || pbio_os_timer_is_expired(&timer));
-
-    if (pbio_os_timer_is_expired(&timer)) {
-        // Transmission has taken too long, so reset the state to allow
-        // new transmissions. This can happen if the host stops reading
-        // data for some reason. This need some time to complete, so delegate
-        // the reset back to the process.
-        return PBIO_ERROR_TIMEDOUT;
+    PBIO_OS_AWAIT_UNTIL(state, !transmitting || cancel);
+    if (transmitting && cancel) {
+        return PBIO_ERROR_CANCELED;
     }
 
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code) {
-
-    static pbio_os_timer_t timer;
+pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code, bool cancel) {
 
     static uint8_t ep1_tx_response_buf[1 + sizeof(uint32_t)] __aligned(4) = { PBIO_PYBRICKS_IN_EP_MSG_RESPONSE };
 
@@ -1066,7 +1056,6 @@ pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t
     }
 
     transmitting = true;
-    pbio_os_timer_set(&timer, PBDRV_USB_TRANSMIT_TIMEOUT);
 
     // Response is just the error code.
     pbio_set_uint32_le(&ep1_tx_response_buf[1], code);
@@ -1076,9 +1065,9 @@ pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t
     usb_setup_tx_dma_desc(CPPI_DESC_TX_RESPONSE, ep1_tx_response_buf, sizeof(ep1_tx_response_buf));
 
     // Wait until complete or trigger reset on timeout.
-    PBIO_OS_AWAIT_UNTIL(state, !transmitting || pbio_os_timer_is_expired(&timer));
-    if (pbio_os_timer_is_expired(&timer)) {
-        return PBIO_ERROR_TIMEDOUT;
+    PBIO_OS_AWAIT_UNTIL(state, !transmitting || cancel);
+    if (transmitting && cancel) {
+        return PBIO_ERROR_CANCELED;
     }
 
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
diff --git a/lib/pbio/drv/usb/usb_nxt.c b/lib/pbio/drv/usb/usb_nxt.c
index 6cfe22dfa..b9678900f 100644
--- a/lib/pbio/drv/usb/usb_nxt.c
+++ b/lib/pbio/drv/usb/usb_nxt.c
@@ -853,9 +853,7 @@ pbdrv_usb_bcd_t pbdrv_usb_get_bcd(void) {
     return PBDRV_USB_BCD_NONE;
 }
 
-pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size) {
-
-    static pbio_os_timer_t timer;
+pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size, bool cancel) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -864,20 +862,17 @@ pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uin
     //     return PBIO_ERROR_BUSY;
     // }
 
-    pbio_os_timer_set(&timer, PBDRV_USB_TRANSMIT_TIMEOUT);
     pbdrv_usb_nxt_write_data(2, data, size);
 
-    PBIO_OS_AWAIT_UNTIL(state, pbdrv_usb_nxt_state.status == USB_READY || pbio_os_timer_is_expired(&timer));
-    if (pbio_os_timer_is_expired(&timer)) {
-        return PBIO_ERROR_TIMEDOUT;
+    PBIO_OS_AWAIT_UNTIL(state, pbdrv_usb_nxt_state.status == USB_READY || cancel);
+    if (pbdrv_usb_nxt_state.status != USB_READY && cancel) {
+        return PBIO_ERROR_CANCELED;
     }
 
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code) {
-
-    static pbio_os_timer_t timer;
+pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code, bool cancel) {
 
     static uint8_t usb_response_buf[PBIO_PYBRICKS_USB_MESSAGE_SIZE(sizeof(uint32_t))] __aligned(4) = { PBIO_PYBRICKS_IN_EP_MSG_RESPONSE };
 
@@ -888,13 +883,12 @@ pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t
     //     return PBIO_ERROR_BUSY;
     // }
 
-    pbio_os_timer_set(&timer, PBDRV_USB_TRANSMIT_TIMEOUT);
     pbio_set_uint32_le(&usb_response_buf[1], code);
     pbdrv_usb_nxt_write_data(2, usb_response_buf, sizeof(usb_response_buf));
 
-    PBIO_OS_AWAIT_UNTIL(state, pbdrv_usb_nxt_state.status == USB_READY || pbio_os_timer_is_expired(&timer));
-    if (pbio_os_timer_is_expired(&timer)) {
-        return PBIO_ERROR_TIMEDOUT;
+    PBIO_OS_AWAIT_UNTIL(state, pbdrv_usb_nxt_state.status == USB_READY || cancel);
+    if (pbdrv_usb_nxt_state.status != USB_READY && cancel) {
+        return PBIO_ERROR_CANCELED;
     }
 
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
diff --git a/lib/pbio/drv/usb/usb_simulation.c b/lib/pbio/drv/usb/usb_simulation.c
index cc2b2a466..e7f43072b 100644
--- a/lib/pbio/drv/usb/usb_simulation.c
+++ b/lib/pbio/drv/usb/usb_simulation.c
@@ -29,7 +29,7 @@ pbdrv_usb_bcd_t pbdrv_usb_get_bcd(void) {
     return PBDRV_USB_BCD_NONE;
 }
 
-pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size) {
+pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size, bool cancel) {
 
     static pbio_os_timer_t timer;
 
@@ -53,7 +53,7 @@ pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uin
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code) {
+pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code, bool cancel) {
 
     static pbio_os_timer_t timer;
 
diff --git a/lib/pbio/drv/usb/usb_simulation_pico.c b/lib/pbio/drv/usb/usb_simulation_pico.c
index 0ec579501..d4703f847 100644
--- a/lib/pbio/drv/usb/usb_simulation_pico.c
+++ b/lib/pbio/drv/usb/usb_simulation_pico.c
@@ -38,7 +38,7 @@ pbdrv_usb_bcd_t pbdrv_usb_get_bcd(void) {
     return PBDRV_USB_BCD_NONE;
 }
 
-pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size) {
+pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size, bool cancel) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -54,7 +54,10 @@ pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uin
             pbdrv_usb_simulation_tx_ready = false;
             // Enable TX interrupt to be notified when ready.
             hw_set_bits(&uart_get_hw(uart_default)->imsc, 1 << UART_UARTIMSC_TXIM_LSB);
-            PBIO_OS_AWAIT_UNTIL(state, pbdrv_usb_simulation_tx_ready);
+            PBIO_OS_AWAIT_UNTIL(state, pbdrv_usb_simulation_tx_ready || cancel);
+            if (!pbdrv_usb_simulation_tx_ready && cancel) {
+                return PBIO_ERROR_CANCELED;
+            }
         }
 
         uart_get_hw(uart_default)->dr = data[i];
@@ -63,7 +66,7 @@ pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uin
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code) {
+pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code, bool cancel) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
diff --git a/lib/pbio/drv/usb/usb_stm32.c b/lib/pbio/drv/usb/usb_stm32.c
index b474d3438..d045ecc71 100644
--- a/lib/pbio/drv/usb/usb_stm32.c
+++ b/lib/pbio/drv/usb/usb_stm32.c
@@ -292,48 +292,50 @@ pbio_error_t pbdrv_usb_tx_reset(pbio_os_state_t *state) {
     return PBIO_SUCCESS;
 }
 
-pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size) {
-
-    static pbio_os_timer_t timer;
+pbio_error_t pbdrv_usb_tx_event(pbio_os_state_t *state, const uint8_t *data, uint32_t size, bool cancel) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
+    if (cancel) {
+        return PBIO_ERROR_CANCELED;
+    }
+
     if (transmitting) {
         return PBIO_ERROR_BUSY;
     }
 
     transmitting = true;
-    pbio_os_timer_set(&timer, PBDRV_USB_TRANSMIT_TIMEOUT);
     USBD_Pybricks_TransmitPacket(&husbd, (uint8_t *)data, size);
-    PBIO_OS_AWAIT_UNTIL(state, !transmitting || pbio_os_timer_is_expired(&timer));
+    PBIO_OS_AWAIT_UNTIL(state, !transmitting || cancel);
 
-    if (pbio_os_timer_is_expired(&timer)) {
-        return PBIO_ERROR_TIMEDOUT;
+    if (transmitting && cancel) {
+        return PBIO_ERROR_CANCELED;
     }
 
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code) {
-
-    static pbio_os_timer_t timer;
+pbio_error_t pbdrv_usb_tx_response(pbio_os_state_t *state, pbio_pybricks_error_t code, bool cancel) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
+    if (cancel) {
+        return PBIO_ERROR_CANCELED;
+    }
+
     if (transmitting) {
         return PBIO_ERROR_BUSY;
     }
 
     transmitting = true;
-    pbio_os_timer_set(&timer, PBDRV_USB_TRANSMIT_TIMEOUT);
 
     pbio_set_uint32_le(&usb_response_buf[1], code);
 
     USBD_Pybricks_TransmitPacket(&husbd, usb_response_buf, sizeof(usb_response_buf));
 
-    PBIO_OS_AWAIT_UNTIL(state, !transmitting || pbio_os_timer_is_expired(&timer));
-    if (pbio_os_timer_is_expired(&timer)) {
-        return PBIO_ERROR_TIMEDOUT;
+    PBIO_OS_AWAIT_UNTIL(state, !transmitting || cancel);
+    if (transmitting && cancel) {
+        return PBIO_ERROR_CANCELED;
     }
 
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
diff --git a/lib/pbio/platform/prime_hub/pbdrvconfig.h b/lib/pbio/platform/prime_hub/pbdrvconfig.h
index f29a1532d..ea16ea21e 100644
--- a/lib/pbio/platform/prime_hub/pbdrvconfig.h
+++ b/lib/pbio/platform/prime_hub/pbdrvconfig.h
@@ -128,7 +128,7 @@
 #define PBDRV_CONFIG_USB_PROD_STR                   LEGO_USB_PROD_STR_TECHNIC_LARGE_HUB " + Pybricks"
 #define PBDRV_CONFIG_USB_STM32F4                    (1)
 #define PBDRV_CONFIG_USB_STM32F4_HUB_VARIANT_ADDR   0x08007d80
-#define PBDRV_CONFIG_USB_CHARGE_ONLY                (1)
+#define PBDRV_CONFIG_USB_CHARGE_ONLY                (0)
 
 #define PBDRV_CONFIG_STACK                          (1)
 #define PBDRV_CONFIG_STACK_EMBEDDED                 (1)