42 USB CDC (Serial) Device
42 : USB CDC (Serial) Device
- Author: Uri Shaked
- Description: USB to UART bridge, 115200 baud rate
- GitHub repository
- Open in 3D viewer
- Clock: 48000000 Hz
How it works
A USB CDC to UART bridge, based on tinyfpga_bx_usbserial.
How to test
- Connect
usb_pandusb_npins to D+ / D- USB pins either through 68 ohm resistors or directly (the resistors are recommended, but not mandatory). - Connect a 1.5k ohm resistor between
dp_pu_oandusb_p(D+). - Connect the RX and TX pins to a UART device or to a logic analyzer.
- Set the clock frequency to 48 MHz.
The device should appear as a serial port on your computer, with vendor_id=1209 and product_id=5454 (https://pid.codes/1209/5454/). The baud rate for the UART interface is hardcoded at 115200.
Demo mode
Set ui_in[0] high to enable demo mode. In this mode, the device sends "Tiny Tapeout!" over USB once per second. UART RX input is ignored while demo mode is active.
External Hardware
USB breakout board, 1.5k ohm resistor
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | demo_mode | usb_p | |
| 1 | usb_n | ||
| 2 | dp_pu_o | ||
| 3 | RX | ||
| 4 | TX | ||
| 5 | |||
| 6 | |||
| 7 | configured |