rfEchoTx Example

Example Summary

In this example you will learn how to setup the radio to do bi-directional communication. The Echo TX example the radio to transmit a packet and then switch over to the receiver mode and wait for its echo. This example is meant to be used with the Echo RX example or SmartRF Studio. For every packet echo, Board_PIN_LED1 is toggled. The frequency and other RF settings can be modified using SmartRF Studio.

Peripherals Exercised

• Board_PIN_LED1 - Blinking indicates a successful transmission and reception of a packet (echo)
• Board_PIN_LED2 - Indicates an abort occurred in packet reception (waiting for the echo)
• Board_PIN_LED1 & Board_PIN_LED2 indicate an error condition

Resources & Jumper Settings

If you’re using an IDE (such as CCS or IAR), please refer to Board.html in your project directory for resources used and board-specific jumper settings. Otherwise, you can find Board.html in the directory <SDK_INSTALL_DIR>/source/ti/boards/<BOARD>.

Example Usage

The user will require two launchpads, one running rfEchoTx (Board_1), another running rfEchoRx (Board_2). Run Board_2 first, followed by Board_1. Board_1 is set to transmit a packet every second while Board_2 is set to receive the packet and then turnaround and transmit it after a delay of 100ms. Board_PIN_LED1 on Board_1 will toggle when it’s able to successfully transmits a packet, and when it receives its echo. Board_PIN_LED2 on Board_2 will toggle when it receives a packet, and then when its able to re-transmit it (see figure 1).

If the receiver (Board_2) is turned off and the rfEchoTx (Board_1) begins transmitting, it switches over to the receiver mode waiting for an echo that will never come; in this situation a timeout timer is started and if no packet is received within 300ms the receiver operation is aborted. This condition is indicated by Board_PIN_LED1 being cleared and Board_PIN_LED2 being set (see figure 2).

If the receiver continues to stay turned off then the rfEchoTx example will alternate between transmitting and aborted receiver operations. Board_PIN_LED1 and Board_PIN_LED2 will start alternating, as seen in figure 3.

An error in transmission of a packet, or the reception of its echo, is indicated by both LEDs going high (see figure 4).

Application Design Details

This examples consists of a single task and the exported SmartRF Studio radio settings.

The default frequency is 868.0 MHz (433.92 MHz for the CC1350-LAUNCHXL-433 board). In order to change frequency, modify the smartrf_settings.c file. This can be done using the code export feature in Smart RF Studio, or directly in the file.

When the task is executed it:

1. Configures the radio for Proprietary mode
2. Gets access to the radio via the RF drivers RF_open
3. Sets up the radio using CMD_PROP_RADIO_DIV_SETUP command
4. Set the output power to 14 dBm (requires that CCFG_FORCE_VDDR_HH = 1 in ccfg.c)
5. Sets the frequency using CMD_FS command
6. Create packet (with increasing sequence number and random content)
7. Set absolute TX time to utilize automatic power management
8. Transmit packet using CMD_PROP_TX command with blocking RF driver call, in which case Board_PIN_LED1 is toggled. The transmit command is chained with the receive command, CMD_PROP_RX, which runs immediately after the packet is transmitted
9. The radio waits for the echo and there are three possibilities

a. echo is successfully received and Board_PIN_LED1 is toggled

b. receive operation times out and Board_PIN_LED2 is set

c. unexpected radio event, an error, in which case both LEDs are set

1. Transmit packets forever by repeating step 6-9

Note for IAR users: When using the CC1310DK, the TI XDS110v3 USB Emulator must be selected. For the CC1310_LAUNCHXL, select TI XDS110 Emulator. In both cases, select the cJTAG interface.