Using the serial port as an E100 console

One reason debugging E100 programs is hard is because it's hard to display output (other than small amounts of output to the LEDs, hexdigits, and LCD module). This web page explains how to print output to a console, as you would in other programming environments.

The basic idea is to use the E100's serial port as a console. This involves two parts:

1. Send the ASCII values for the characters you want to print to the serial console. E.g., to print abc, send the numbers 97, 98, 99. To print a newline, send the values 13 (carriage return) and 10 (linefeed). If you want to display numeric values, you'll have to convert the number to a series of ASCII values. E.g., to display the number 123, you could send the values 49, 50, 51. It's easiest to display the number in hexadecimal, because you can easily isolate each digit with shift and add instructions.
2. Receive and display the sent characters on another device. This other device could be a virtual serial console (with ase100) or another computer.
   • ase100 can connect the serial port to a virtual serial console, which will display characters that are sent to the serial port. In addition, any characters you type in the serial console window will be sent to the E100 and can be received via the serial_receive controller. To connect to a virtual serial console, enter a blank name for the name of the serial port.
   • If you are running on a DE2-115 board, connect the DE2-115's serial port to a Linux computer. If the Linux computer lacks a serial port, use a USB-serial converter and replace /dev/ttyS0 with /dev/ttyUSB0 in the commands below. To display the data sent to the Linux computer, run the following commands on the Linux computer:

     stty -F /dev/ttyS0 speed 115200 raw cs8
     cat /dev/ttyS0
     

For more information, see Lab 7's handout on serial communication