stmhal: Fix USB CDC-only mode under Windows.

This fix adds PIDs 9801 and 9802 to the pybcdc.inf file.

When in CDC only mode, it presents itself as a Communcations
device rather than as a composite device. Presenting as a
composite device with only the CDC interface seems to confuse
windows.

To test and make sure that the correct pybcdc.inf was being used,
I used USBDeview from http://www.nirsoft.net/utils/usb_devices_view.html
to uninstall any old pyboard drivers (Use Control-F and search
for pyboard). I found running USBDeview as administrator worked best.

Installing the driver in CDC+MSC mode first is recommended (since the
pybcdc.inf file in on the internal flash drive). Then when you switch
modes everything seems to work properly.

I used https://github.com/dhylands/upy-examples/blob/master/boot_switch.py
to easily switch the pyboard between the various USB modes for testing.

1 files changed, 14 insertions, 1 deletions

diff --git a/stmhal/usbd_desc.c b/stmhal/usbd_desc.c
index 2b8a79b15..9f2a84162 100644
--- a/stmhal/usbd_desc.c
+++ b/stmhal/usbd_desc.c
@@ -81,7 +81,20 @@ __ALIGN_BEGIN static uint8_t USBD_LangIDDesc[USB_LEN_LANGID_STR_DESC] __ALIGN_EN
 __ALIGN_BEGIN static uint8_t USBD_StrDesc[USBD_MAX_STR_DESC_SIZ] __ALIGN_END;
 
 // set the VID, PID and device release number
-void USBD_SetVIDPIDRelease(uint16_t vid, uint16_t pid, uint16_t device_release_num) {
+void USBD_SetVIDPIDRelease(uint16_t vid, uint16_t pid, uint16_t device_release_num, int cdc_only) {
+    if (cdc_only) {
+        // Make it look like a Communications device if we're only
+        // using CDC. Otherwise, windows gets confused when we tell it that
+        // its a composite device with only a cdc serial interface.
+        hUSBDDeviceDesc[4] = 0x02;
+        hUSBDDeviceDesc[5] = 0x00;
+        hUSBDDeviceDesc[6] = 0x00;
+    } else {
+        // For the other modes, we make this look like a composite device.
+        hUSBDDeviceDesc[4] = 0xef;
+        hUSBDDeviceDesc[5] = 0x02;
+        hUSBDDeviceDesc[6] = 0x01;
+    }
     hUSBDDeviceDesc[8] = LOBYTE(vid);
     hUSBDDeviceDesc[9] = HIBYTE(vid);
     hUSBDDeviceDesc[10] = LOBYTE(pid);