Report some possible improvement for USBTTL splitter #40
Description
I'm doing some intensive development on NOR flash-based firmware. I have a CH335F USB hub that I can control the power of the downstream ports, and I send '2' during power up to kick the tinyvision to bootloader mode.
The following 2 improvements are suggested:
- Separate the UART power and USB power. For the current design, the UART USB power goes to the upstream tinyvision USB port, then the downstream tinyvision USB port, then the CH340. There is no way to keep the CH340 running while switching the power on the Tinyvision. I need to make 2 cuts and route the power from UART power to CH340N.
A new version should only has the UART power to CH340N. And the power between tinyvision upstream and downstream. There can be a 0 ohm resistor to connect these 2 networks in some cases which they should be connected.
- The 78L05 should be changed to some modern LDO. The 78L05 has 1.7V drop voltage and the CH340N will start to fail when the USB voltage drops to 4.6V. Using an XC6206-3.3 fix this issue.