FTDI serial

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This is the documentation page for the FTDI-serial board.


The FTDI-serial board has an USB connector and a 4-pin serial/UART connector. The brains of the PCB is an FT232RL chip.

For references to left-right, and top-bottom in this page, please hold the board with the USB connector on the left and the serial connector on the right.

External resources


The 4 pin connector is connected as follows

1Ground (G)
2Rx (R)do not drive at 5V level if jumper is set to 3.3v.
probably works if driven at 3.3V with jumper at 5V.
3Tx (T)works at 5V or 3.3V level depening on jumper
4V+5V or 3.3V depending on jumper
  • led1 is connected to CBUS0 (Tx activity)
  • led2 is connected to CBUS1 (Rx activity)
  • led3 is connected to VCC

Jumper settings

IO voltage
1-2: 3V3 (jumper on the side nearest the chip and USB connector)
2-3: 5V (jumper near the serial connector)

This switches the "VCCIO" pin on the FT232RL chip, as well as the "V+" pin on the serial connector.

At the 3.3V setting you're allowed to draw up to 50mA from this pin.

At the 5V setting, you can use whatever the USB bus allows. Officially that would probably be 100mA, as the FTDI chip, by default, doesn't ask for more. However, in practise you can very often get away with drawing as much as 500mA (even without asking). You can program the chip to ask for more by programming the eeprom of the chip using an FTDI programming utility.

Future hardware enhancements

Allow "hacker" access to more IOs on the FTDI chip with "test pads" on the bottom of the PCB.



  • Size reduced considerably
  • Added an VCC pin to the Rx/Tx connector


  • Initial public release