Silicon Labs CP2104 : Not Recommended for New Designs (NRND) SINGLE-CHIP USB-TO-UART BRIDGE : Datasheet https://www.silabs.com/documents/public/data-sheets/cp2104.pdf For newer designs, the CP2102N devices offer compatible footprints and are recommended for use instead of the CP2104. HOWEVER, this is NOT a “Drop In” Replacement ! Resistor Divider Network required on Vbus and ESD protection devices (watch video) See the Silicon Labs website (www.silabs.com/usbxpress) for more information. Limor Fried, AC2SN discusses Replacements for the SiLabs CP2104 Bridge Chip, found in many Amateur Radio accessories (and some radios). Looking for a CHEAP USB-to-UART Bridge Chip Solution? Consider the Silicon Labs CP2102N-MINIEK, MSRP $7.99 CP2102N USBXpress Bridge Mini Development Kit https://www.silabs.com/development-tools/interface/cp2102n-mini-development-kit User’s Guide UG254 https://www.silabs.com/documents/public/user-guides/ug254-cp2102n-miniek.pdf What is UART ? Why is this Important? Amateur Radio transceivers and Accessories began to incorporate Micro-controllers and Microprocessors in the mid-1970s (iCOM IC-211 one example). By the 1980s, new transceiver designs incorporated microprocessors, with had UART for external communications. Initially UART-to-Serial (RS232 or RS485) bridge chips (Maxim 232 chips) were widely available. USB would be created by Intel in 1996. A universal asynchronous receiver-transmitter (UART /ˈjuːɑːrt/) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significant to the most significant, framed by start and stop bits so that precise timing is handled by the communication channel. The electric signaling levels are handled by a driver circuit external to the UART.