pbdrv/usb: Add support for transmitting stdout over USB.

Add partial support for transmitting stdout messages over USB.

TODO: Need to add implementation of subscribing to have this not enabled
all of the time. Then this can be integrated with the mphal in MicroPython.

Signed-off-by: Nate Karstens <[email protected]>

Author: nkarstens

lib/pbio/drv/usb/usb_stm32.c

@@ -32,9 +32,11 @@ PROCESS(pbdrv_usb_process, "USB");
 static uint8_t usb_in_buf[USBD_PYBRICKS_MAX_PACKET_SIZE] __aligned(4);
 static uint8_t usb_response_buf[1 + sizeof(uint32_t)] __aligned(4);
 static uint8_t usb_status_buf[1 + PBSYS_STATUS_REPORT_SIZE] __aligned(4);
+static uint8_t usb_stdout_buf[USBD_PYBRICKS_MAX_PACKET_SIZE] __aligned(4);
 static volatile uint32_t usb_in_sz;
 static volatile uint32_t usb_response_sz;
 static volatile uint32_t usb_status_sz;
+static volatile uint32_t usb_stdout_sz;
 static volatile bool transmitting;
 
 static USBD_HandleTypeDef husbd;
@@ -137,6 +139,52 @@ void pbdrv_usb_stm32_handle_vbus_irq(bool active) {
     process_poll(&pbdrv_usb_process);
 }
 
+/**
+ * Queues data to be transmitted via USB.
+ * @param data  [in]        The data to be sent.
+ * @param size  [in, out]   The size of @p data in bytes. After return, @p size
+ *                          contains the number of bytes actually written.
+ * @return                  ::PBIO_SUCCESS if @p data was queued, ::PBIO_ERROR_AGAIN
+ *                          if @p data could not be queued at this time (e.g. buffer
+ *                          is full), ::PBIO_ERROR_INVALID_OP if there is not an
+ *                          active USB connection or ::PBIO_ERROR_NOT_SUPPORTED
+ *                          if this platform does not support USB.
+ */
+pbio_error_t pbdrv_usb_stdout_tx(const uint8_t *data, uint32_t *size) {
+    uint8_t *ptr = usb_stdout_buf;
+    uint32_t ptr_len = sizeof(usb_stdout_buf);
+
+    // TODO: return PBIO_ERROR_INVALID_OP if app flag is not set. Also need a
+    // timeout in case the app crashes and doesn't clear the flag on exit.
+
+    if (usb_stdout_sz) {
+        return PBIO_ERROR_AGAIN;
+    }
+
+    *ptr++ = USBD_PYBRICKS_IN_EP_MSG_EVENT;
+    ptr_len--;
+
+    *ptr++ = PBIO_PYBRICKS_EVENT_WRITE_STDOUT;
+    ptr_len--;
+
+    *size = MIN(*size, ptr_len);
+    memcpy(ptr, data, *size);
+
+    usb_stdout_sz = 1 + 1 + *size;
+
+    process_poll(&pbdrv_usb_process);
+
+    return PBIO_SUCCESS;
+}
+
+/**
+ * Indicates if there is stdout data waiting to be transmitted over USB.
+ * @retval  false if stdout data is currently being transmitted.
+ */
+bool pbdrv_usb_stdout_tx_is_idle(void) {
+    return usb_stdout_sz == 0;
+}
+
 /**
   * @brief  Pybricks_Itf_Init
   *         Initializes the Pybricks media low layer
@@ -148,6 +196,7 @@ static USBD_StatusTypeDef Pybricks_Itf_Init(void) {
     usb_in_sz = 0;
     usb_response_sz = 0;
     usb_status_sz = 0;
+    usb_stdout_sz = 0;
     transmitting = false;
 
     return USBD_OK;
@@ -197,6 +246,8 @@ static USBD_StatusTypeDef Pybricks_Itf_TransmitCplt(uint8_t *Buf, uint32_t Len,
         usb_response_sz = 0;
     } else if (Buf == usb_status_buf) {
         usb_status_sz = 0;
+    } else if (Buf == usb_stdout_buf) {
+        usb_stdout_sz = 0;
     } else {
         ret = USBD_FAIL;
     }
@@ -314,7 +365,7 @@ PROCESS_THREAD(pbdrv_usb_process, ev, data) {
 
         new_status_flags = pbsys_status_get_flags();
 
-        // Transmit. Give priority to response, then status updates.
+        // Transmit. Give priority to response, then status updates, then stdout.
         if (usb_response_sz) {
             transmitting = true;
             USBD_Pybricks_TransmitPacket(&husbd, usb_response_buf, usb_response_sz);
@@ -329,6 +380,9 @@ PROCESS_THREAD(pbdrv_usb_process, ev, data) {
 
             transmitting = true;
             USBD_Pybricks_TransmitPacket(&husbd, usb_status_buf, usb_status_sz);
+        } else if (usb_stdout_sz) {
+            transmitting = true;
+            USBD_Pybricks_TransmitPacket(&husbd, usb_stdout_buf, usb_stdout_sz);
         }
     }
 

lib/pbio/include/pbdrv/usb.h

@@ -9,7 +9,10 @@
 #ifndef _PBDRV_USB_H_
 #define _PBDRV_USB_H_
 
+#include <stdbool.h>
+
 #include <pbdrv/config.h>
+#include <pbio/error.h>
 
 /**
  * Indicates battery charging capabilites that were detected on a USB port.
@@ -37,12 +40,32 @@ typedef enum {
  */
 pbdrv_usb_bcd_t pbdrv_usb_get_bcd(void);
 
+/**
+ * Transmits the given buffer over the USB stdout stream.
+ * @return              The result of the operation.
+ */
+pbio_error_t pbdrv_usb_stdout_tx(const uint8_t *data, uint32_t *size);
+
+/**
+ * Indicates if the USB stdout stream is idle.
+ * @return              true if the USB stdout stream is idle.
+*/
+bool pbdrv_usb_stdout_tx_is_idle(void);
+
 #else // PBDRV_CONFIG_USB
 
 static inline pbdrv_usb_bcd_t pbdrv_usb_get_bcd(void) {
     return PBDRV_USB_BCD_NONE;
 }
 
+static inline pbio_error_t pbdrv_usb_stdout_tx(const uint8_t *data, uint32_t *size) {
+    return PBIO_SUCCESS;
+}
+
+static inline bool pbdrv_usb_stdout_tx_is_idle(void) {
+    return true;
+}
+
 #endif // PBDRV_CONFIG_USB
 
 #endif // _PBDRV_USB_H_