Problem solved. You have to initialize some bits to zero in UHCI_CONF1_REG as well. Note that setting the whole register to 0 causes a DMA Descriptor error. You have to set the bits individually. The code below works for me: lldesc_t widget_usb_Msg; uint8_t dma_test_msg[8] __attribute__((aligned(32)...

Let me qualify that. The DMA transfers data. But the 1st byte is not sent. And the 4th byte is not sent correctly. Here is my code: lldesc_t widget_usb_Msg; uint8_t dma_test_msg[8] __attribute__((aligned(32))) = { 49,50,51,52,53,54,55,56 }; void init_dmaDesc() { periph_module_enable(PERIPH_UHCI0_MOD...

I got it to work.

There was a problem with the DMA descriptor. Checking the raw interrupt register was helpful. Also it turns out that resetting the fifo was not helpful.

bump. still need to use dma with uart.

3 weeks later....

Did anyone look at this code?

I use the UART_TX_DONE_INT successfully in my application with no issues such as you describe.

I only enable the interrupt after filling the UART buffer, i.e. after transmission is already started.

OK here is relevant code. Note that the UART functions correctly if I don't define USE_DMA: void uart_intr_setup(void){ state = STARTUP; reset_mem(); config(); periph_module_enable(PERIPH_UHCI0_MODULE); init_dmaDesc(); esp_err_t ret; uart_param_config(uart_num, &uart_config); ret = uart_set_pin(uart...

Thanks for helping. Actually it is part of a much larger project which I would not, for reasons of confidentiality, want to post. We are talking about thousands of lines of code.

I will try to take the relevant parts and make an independent project out of it for test purposes.

Still no dice. I notice that DMA routines for I2S and SPI reset the bus before start. Not sure why the reset bits in the UHCI configuration register are marked reserved in the TRM, but enumerated in the esp-idf include files. Anyway I tried it both ways. No signal. You wrote somewhere else that you ...

Sorry I didn't see your comment about the bitfields that should be zero until just now. It appears that there might be an error in uhci_struct.h . There are a number of bitfields in the struct that are not in the TRM. For example UHCI_OUT_DATA_BURST_EN, UHCI_OUTDSCR_BURST_EN and UHCI_INDSCR_BURST_EN...