UPDI Programmer

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The UPDI programmer is a serial based programmer.

You need to select 115200 BAUD and the COM port which is connected to the UPDI interface.

In version 2084 you can select up to 225000 baud. This is the maximum recommended baud from microchip with the default clock.


The UPDI interface is very simple : all you need is a TX, RX and a resistor.

Connect TX from the PC UART to a 4K7 resistor. The other side of the resistor is connected to the PC RX and to the UPDI pin of the processor.

We use DTR to switch the TX and RX from the PC to the processor. This allows to use the PC COM port to be used for serial communication and as a UPDI programmer.


Note : some modules will not give proper signals. A 1K resistor will bring better results.


noticePlease notice that you need a MAX232 or other level converter between the PC communication pins to create the proper voltage level! Like the circuit shown below.


The programmer works similar as the other supported programmers : you can program the FLASH, EEPROM and the fuse/lock bytes


In version 2083 you can also write the fuse bytes.




When you change the values of a fuse the WRITE-FUSES button will be enabled.

When you change the value of the LOCK fuse, the WRITE-LOCK bits  button will be enabled.

When you change the value of the user fuses, the WRITE USER ROW button will be enabled.


When you write the fuses, the fuse values will be re-read (refreshed). And the same for the other fuses.




A typical connection for the UPDI programmer :




A MAX232 level converter will convert the RS232 levels to 5V.

The TX from the PC/max232 is connected with a 4K7(or 1K) resistor to the UPDI pin.

The RX from the PC/max232 is connected directly to the UPDI pin.


you can also use an USB virtual com port chip such as the FT232 or CP2102.


Using a serial port just for programming is a bit of a waste. Often you also like to have serial communications.

So a more practical programmer will switch the TX/RX lines between the UPDI pin and the TX-RX USART pins of the processor.




Notice that the USB circuit shown is not complete, you should check it with the chip of your choice like FT232RL, CP2102, etc. The main purpose of the USB part is to show the TX/RX and DTR pins.


The TX pin and RX pins are connected to a 4053 switch. This is an analog switch. The DTR line selects the XYZ-0 or XYZ-1 side of the switch.

The UPDI pin is also connected to a MUX switch. This simple circuit now switches between the UPDI mode and the TX and RX pins of the processor.

The BASCOM-UPDI programmer will automatically switch the DTR line.