USB speed testing and results

The writes to cdc stall at first and then at the end it goes
really smoothly, wonder why that is...

DMA transfer size fits bulk packet size, 4kB overall buffer

src/ice_usb_uart.c

@@ -31,7 +31,7 @@ struct uart_wrap {
 // uart -> rb (irq)
 //   rb -> cdc
 
-#define DMA_TCNT        128
+#define DMA_TCNT        512
 #define DMA_ALARM_US    (100*1000) // 100 ms
 
 static void ice_usb_uart_rx_dma_irq0(struct uart_wrap* uart, int channel) {
@@ -106,7 +106,7 @@ static void ice_usb_uart_dma_flush_alarm(struct uart_wrap* uart) {
         dma_channel_set_trans_count(ch_busy, DMA_TCNT, true);
 
         uart->dma_last_transfer = get_absolute_time();
-        printf("elapsed %dms ack %d\n", elapsed_us/1000, tr_done);
+        // printf("elapsed %dms ack %d\n", elapsed_us/1000, tr_done);
     }
     // else printf("No\n");
 
@@ -164,11 +164,13 @@ static void ice_usb_uart_rx_to_cdc(struct uart_wrap* uart) {
         if (bufsize == 0)
             break; // cdc buffer full
 
+        printf("%lu %4d\n", time_us_32(), bufsize);
+
         // ack data that was sent to cdc
         rb_read_ack(&uart->rx_buf, bufsize);
+        // flush
+        tud_cdc_n_write_flush(uart->itf);
     }
-
-    tud_cdc_n_write_flush(uart->itf);
 }
 
 

src/ice_usb_uart.h

@@ -6,7 +6,7 @@
 #include "tusb.h"
 #include "tusb_config.h"
 
-#define ICE_USB_UART_RBBITS 10
+#define ICE_USB_UART_RBBITS 12
 #define ICE_USB_UART_RBSIZE (1<<ICE_USB_UART_RBBITS)
 
 void ice_usb_uart_init();