When wired this way, any bytes that you send out the USART from inside your AVR will show up at the TX pins of the RS232 SPARE connector.
#Codevision avr usart example serial
We had to pull the blue plastic cover back a little on the USB to Serial adapters to get them to both fit on the DB9 connectors.
Here is how your serial ports should be set up. The ATmega32 uses PD0 and PD1 for serial communications, and the TXD/RXD pins on the STK500 are tied to some logic (a MAX202 to be exact) that connects to RS232 SPARE. Connect a two wire jumper cable from PD0 (that’s PORTD, Bit 0) to RXDand PD1 (that’s PORTD, Bit 1) to TXD, as is done in the picture below with the blue and white cable. Last, you need to connect the ATmega32’s TX and RX pins to the spare serial port on your STK500.We use Trendnet TU-S9 USB to Serial cables for this with no problems. You must connect a second serial cable to the serial port labeled RS232 SPARE, and connect the other end of that cable to an unused serial port on your computer.We will use them in the example program listing at the end of this guide.