How to configure STM32F103 USB endpoints.

[Bags]

Been reading thru the F103 datasheet to try and figure out why my TinyUSB based code isn't working. The datasheet says.. "For mono-directional/single-buffer endpoints, a single register can be used to implement two distinct endpoints".

The F103 has 8 physical endpoint registers. There are no flags in those registers to set mono or bidirectional mode. Each register only holds one EP address value.

My application requires creating EP0 (IN+OUT) + 4 * (Bulk IN+Bulk OUT+Interrupt In)=2+4*(1+1+1)= 14 EP addresses in total.

The datasheet continues on to say "The number of registers is 8, allowing up to 16 mono-directional/single-buffer or up to 7 double-buffer endpoints(a) in any combination. For example the USB peripheral can be programmed to have 4 double buffer endpoints and 8 single-buffer/mono-directional endpoints."

So how can you get 14 EP addresses into 8 endpoint registers?

[TDK]

> The datasheet continues on to say "The number of registers is 8, allowing up to 16 mono-directional/single-buffer or up to 7 double-buffer endpoints(a) in any combination. For example the USB peripheral can be programmed to have 4 double buffer endpoints and 8 single-buffer/mono-directional endpoints."

Can you link to the datasheet that says this? I can't find it. "STM32F103" unfortunately doesn't narrow down a single datasheet.

Here is a F103 datasheet that does not say this. Checked a few others as well.

https://www.st.com/resource/en/datasheet/stm32f103ze.pdf

> So how can you get 14 EP addresses into 8 endpoint registers?

I suspect it is not possible to have 14 independent endpoint addresses.

In any case:

[gbm]

In F103, you may configure up to 8 pairs of IN+OUT endpoints (or 8 double-buffered, single direction endpoints), so the maximum possible no. of CDC VCPs is 3 (Control IN+OUT, 3*CDC data IN+OUT, 3*CDC notification IN). Both endpoints in a pair must be of the same type, so you cannot combine interrupt IN with bulk OUT in a single pair. With 3 CDCs, one pair remains free, so you may add some other device, like MSC or printer.