CprE WiFi Bridge

Transcription

1 CprE WiFi Bridge User Guide

2 Table of Contents Introduction Usage Configuration Status LEDs Connecting to the WiFi bridge Command Mode Usage Commands

3 Introduction The CprE 288 WiFi bridge is used to wirelessly connect the TM4C123G microcontroller to the lab computers over WiFi. The WiFi bridge is connected to the spare slot next to the main microcontroller on the cybot baseboard. Figure 1: The WiFi bridge The WiFi bridge makes it easy to stream data between the lab computers and the cybot platform using UART, which is introduced in lab 5. This will be heavily used for the final project.

4 Usage Configuration The WiFi bridge communicates with the TM4C123G over UART with a baud rate of , 8 data bits, 1 stop bit. The TM4C123G also shares a GPIO pin, PB2, which is used for command mode. The UART and GPIO pin must be properly configured before using the WiFi bridge. To use the WiFi bridge, the wireless AP must first be enabled. This is accomplished by putting the bridge in command mode, then sending the WIFI_START command. Some pseudo code for starting the WiFi AP is shown below: WiFi_start() commandpin = 1 //Enter command mode uart_sendchar(wifi_start_command) uart_sendstr(wifi_psk) uart_sendchar(0x00) response = uart_waitforchar() commandpin = 0 //Send command //Send WiFi PSK //NULL terminator //Wait for response //Leave command mode if(response!= 0) { //An error occurred } The process for stopping the WiFi AP is similar: WiFi_stop() commandpin = 1 uart_sendchar(wifi_stop_command) response = uart_waitforchar() commandpin = 0 //Enter command mode //Send command //Wait for response //Leave command mode if(response!= 0) { //An error occurred } More information about command mode can be found in the Command Mode chapter of this document.

5 Status LEDs The WiFi bridge has three status LEDs located on the bottom of the circuit board: Figure 2: From left to right: Green, Orange, and Red status LEDs Each LED indicates the state of a different part of the WiFi bridge system: Green LED Indicates the state of the WiFi AP Off: The AP is stopped Flashing: The AP is started but no station is connected On: The AP is started and a station is connected Orange LED Indicates the state of the TCP socket Off: The socket is not available Flashing: The socket is ready for a connection On: The socket is connected Red LED Indicates that data is being transmitted or received, or a command has been sent

6 Connecting to the WiFi bridge Before connecting, ensure that the AP is started by verifying that the green LED is flashing. You will also need to look at the robot to find its ID number. To connect: 1. On a lab computer, view the list of network connections and select cybot n, where n is the ID of your robot 2. Enter the PSK (password) that was configured what the WiFi AP was started 3. Verify that the green LED is now on, indicating that a station has connected 4. Open PUTTY, and configure the connection (as shown below in figure 3) 5. Verify that the orange LED is now on, indicating that a TCP connection has been established 6. The WiFi bridge is ready to go! Figure 3: PUTTY configuration for WiFi mode

7 Command Mode Usage Command mode is used to send commands to the WiFi bridge. Here is an example program flow for using command mode: 1. Set the command pin (PB2) to high 2. Send the command ID 3. If the command requires a parameter, then a. For a variable-length parameter, send the parameter, followed by a NULL (0) b. For a fixed-length parameter, simply send the parameter (without a NULL terminator) 4. Wait for the WiFi bridge to send a single character response a. Check the result, a non-zero value indicates an error 5. Set the command pin to low Commands ID 0 Name WIFI_START Parameter count 1 Parameter 1 Returns Pre-shared key for WiFi AP (i.e. the network password ). Should be between 8 and 32 characters and null terminated 0 - SUCCESS 1 - INVALID_PSK GENERIC_ERROR ID 1 Name WIFI_STOP Parameter count 0 Returns 0 - SUCCESS GENERIC_ERROR