DMA_ITConfig(DMA1_Stream7, DMA_IT_TC, ENABLE);
I removed all code from the interrupt to make sure their was no conflict in the interrupt call itself and this had no effect. The DMA itself is functioning as I am using it to ramp speed for a motor and the motor speed is ramping as programmed. If do not call the interrupt the system stays connected. If I call the interrupt the USB stops communicating. I also changed streams and channels with same effect. FYI this code has been working for years using the STM32F1.
I am also trying to use a DMA interrupt with the ADC and the interrupt is not being called. The ADC and DMA are working as I can access the data without an interrupt. Same command as above but for DMA2 Stream 0. Not sure if these problems are related. I have not tested the ADC part enough to know if it is only the interrupt.
Thanks for any suggestions. I have examined the USB Virtual COM Port code and have not found any obvious conflicts with the DMA interrupt.