EP_REG(x) registers have a total of 6 toggleable bits. Those bits can only be toggled if we write a one to it, otherwise writing a zero has no effect
This commit fixes all the access to these registers to prevent from modifying these bits when not needed
Signed-off-by: Dylan Laduranty <dylan.laduranty@mesotic.com>
For the usbdev_fs peripheral, IN and OUT endpoints of the same index must have the same type.
For instance, if EP1 OUT is a bulk endpoint, EP1 IN must either be unused or used as bulk too but it cannot be used as interrupt or isochronous.
With the previous check, the following registration pattern (EP OUT Bulk -> EP IN Interrupt -> EP IN Bulk) would assign both EP OUT Bulk and EP IN Interrupt to same endpoint index. So the configuration would be broken.
Applying the same registration pattern with this patch would now produce EP OUT Bulk -> 1 / EP IN Interrupt -> 2 / EP IN Bulk 1. Which is a working configuration for this IP
Signed-off-by: Dylan Laduranty <dylan.laduranty@mesotic.com>
There are two schemes for accessing the packet buffer area (PMA) from the CPU:
- 2 x 16 bit/word access scheme where two 16-bit half-words per word can be accessed. With this scheme the access can be half-word aligned and the PMA address offset corresponds therefore to the local USB IP address. The size of the PMA SRAM is usually 1024 byte.
- 1 x 16 bit/word access scheme where one 16-bit half word per word can be accessed. With this scheme the access can only be word-aligned and the PMA address offset to a half-word is therefore twice the local USB IP address. The size of the PMA SRAM is usually 512 byte.
Which access scheme is used depends on the STM32 model.
The addressing of the Packet buffer Memory Area (PMA) is done locally in the USB IP core in half-words with 16-bit. The `_ep_in_buf` and `_ep_out_buf` arrays which hold these USB IP local addresses in the PMA for initialized EPs therefore always use `uint16_t`.
If the MCU does not have an internal D+ pullup and there is no dedicated GPIO to simulate a USB disconnect, the D+ GPIO is temporarily configured as an output and pushed down to simulate a disconnect/connect cycle to allow the host to recognize the device. However, this requires an external pullup on D+ signal to work
If `RCC_CFGR_USBPRE` is defined, the USB device FS clock of 48 MHz is derived from the PLL clock. In this case the PLL clock must be configured and must be either 48 MHz or 72 MHz. If the PLL clock is 72 MHz it is pre-divided by 1.5, the PLL clock of 48 MHz is used directly.
For a number of STM32 MCUs with the USB-FS device interface the signals USB_DP and USB_DM are not defined as GPIO alternative function but as additional function. Additional functions are directly selected/enabled through peripheral registers hand have not to be configured. In this case, the configuration defines GIO_AF_UNDEF as alternative function.
