rfEasyLinkEchoTx Example

Example Summary

This example demonstrates the use of the EasyLink API in doing bi-directional communication. It will require the use of two boards, one running the rfEasyLinkEchoTx project that will originate the packets, while another board running the rfEasyLinkEchoRx project will re-transmit (echo) them back to the originator.

For more information on the EasyLink API and usage refer to https://processors.wiki.ti.com/index.php/SimpleLink-EasyLink

Peripherals Exercised

For the rfEasyLinkEchoTx (Board_1) project,

• 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

For the rfEasyLinkEchoRx (Board_2) project,

• Board_PIN_LED2 - Blinking indicates a successful reception and re-transmission of a packet (echo)
• Board_PIN_LED1 - Indicates an error in either reception of a packet or in its re-transmission

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>.

System Confirguration Tool (SysConfig) Setup

Driver Configuration

• RF - RF Driver Configuration
  • Hardware Used - RF Antenna Switch
• Power - Power Manager Configuration
  • Default options used
• GPIO - GPIO Configuration
  • Hardware Used: LaunchPad LED Red
• GPIO - GPIO Configuration
  • Hardware Used: LaunchPad LED Green

EasyLink Stack Configuration

• Basic Configuration - Basic EasyLink Stack Configuration
  • Enable Address Filtering - True
  • Addresses to Filter - 0xAA
• RF Settings - PHY Configuration
  • Default PHY - Custom
  • Additional Supported PHYs - Custom

Example Usage

The user will require two launchpads, one running rfEasyLinkEchoTx (Board_1), another running rfEasyLinkEchoRx (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, Board_1 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 on Board_1, while an error on Board_2 will cause it to set Board_PIN_LED1 high and Board_PIN_LED2 low (see figure 4).

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Application Design Details

This example shows how to use the EasyLink API to access the RF driver, set the frequency and transmit packets. The RFEASYLINKTX_ASYNC define is used to select between the Blocking or Async TX/RX API.

The rfEasyLinkEchoTx example will transmit a packet every second while the rfEasyLinkEchoRx will echo all received packets after a delay of 100ms. If Board_1 aborts a packet reception Board_PIN_LED2 is set while Board_PIN_LED1 is cleared. An error condition on Board_1 is indicated by both LEDs going high. An error condition on Board_2 is indicated by Board_LED_1 going high while Board_LED_2 is cleared.

A single task, “rfEasyLinkEchoFnx”, configures the RF driver through the EasyLink API and transmits and receives messages.

EasyLink API

Overview

The EasyLink API should be used in application code. The EasyLink API is intended to abstract the RF Driver in order to give a simple API for customers to use as is or extend to suit their application[Use Cases] (@ref USE_CASES).

General Behavior

Before using the EasyLink API:

• The EasyLink Layer is initialized by calling EasyLink_init(). This initializes and opens the RF driver and configures a modulation scheme passed to EasyLink_init.
• The RX and TX can operate independently of each other.

The following is true for receive operation:

• RX is enabled by calling EasyLink_receive() or EasyLink_receiveAsync()
• Entering RX can be immediate or scheduled
• EasyLink_receive() is blocking and EasyLink_receiveAsync() is non-blocking
• The EasyLink API does not queue messages so calling another API function while in EasyLink_receiveAsync() will return EasyLink_Status_Busy_Error
• An Async operation can be cancelled with EasyLink_abort()

The following apply for transmit operation:

• TX is enabled by calling EasyLink_transmit(), EasyLink_transmitAsync() or EasyLink_transmitCcaAsync()
• TX can be immediate or scheduled
• EasyLink_transmit() is blocking and EasyLink_transmitAsync(), EasyLink_transmitCcaAsync() are non-blocking
• EasyLink_transmit() for a scheduled command, or if TX cannot start
• The EasyLink API does not queue messages so calling another API function while in either EasyLink_transmitAsync() or EasyLink_transmitCcaAsync() will return EasyLink_Status_Busy_Error
• An Async operation can be cancelled with EasyLink_abort()

Error Handling

The EasyLink API will return EasyLink_Status containing success or error code. The EasyLink_Status codes are:

• EasyLink_Status_Success
• EasyLink_Status_Config_Error
• EasyLink_Status_Param_Error
• EasyLink_Status_Mem_Error
• EasyLink_Status_Cmd_Error
• EasyLink_Status_Tx_Error
• EasyLink_Status_Rx_Error
• EasyLink_Status_Rx_Timeout
• EasyLink_Status_Busy_Error
• EasyLink_Status_Aborted

Power Management

The power management framework will try to put the device into the most power efficient mode whenever possible. Please see the technical reference manual for further details on each power mode.

The EasyLink Layer uses the power management offered by the RF driver Refer to the RF Driver documentation for more details.

Supported Functions

| Generic API function          | Description                                        |
|-------------------------------|----------------------------------------------------|
| EasyLink_init()               | Init's and opens the RF driver and configures the  |
|                               | specified settings based on EasyLink_Params struct |
| EasyLink_transmit()           | Blocking Transmit                                  |
| EasyLink_transmitAsync()      | Non-blocking Transmit                              |
| EasyLink_transmitCcaAsync()   | Non-blocking Transmit with Clear Channel Assessment|
| EasyLink_receive()            | Blocking Receive                                   |
| EasyLink_receiveAsync()       | Nonblocking Receive                                |
| EasyLink_abort()              | Aborts a non blocking call                         |
| EasyLink_enableRxAddrFilter() | Enables/Disables RX filtering on the Addr          |
| EasyLink_getIeeeAddr()        | Gets the IEEE Address                              |
| EasyLink_setFrequency()       | Sets the frequency                                 |
| EasyLink_getFrequency()       | Gets the frequency                                 |
| EasyLink_setRfPower()         | Sets the Tx Power                                  |
| EasyLink_getRfPower()         | Gets the Tx Power                                  |
| EasyLink_getRssi()            | Gets the RSSI                                      |
| EasyLink_getAbsTime()         | Gets the absolute time in RAT ticks                |
| EasyLink_setCtrl()            | Set RF parameters, test modes or EasyLink options  |
| EasyLink_getCtrl()            | Get RF parameters or EasyLink options              |
| EasyLink_getIeeeAddr()        | Gets the IEEE address                              |

Frame Structure

The EasyLink implements a basic header for transmitting and receiving data. This header supports addressing for a star or point-to-point network with acknowledgements.

Packet structure:

 _________________________________________________________
|           |                   |                         |
| 1B Length | 1-64b Dst Address |         Payload         |
|___________|___________________|_________________________|

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.

EasyLink Stack Configuration using the System Configuration Tool (SysConfig)

Overview

The purpose of SysConfig is to provide an easy to use interface for configuring drivers, RF stacks, and more. Many parameters of the EasyLink stack can be configured using SysConfig including address filtering, clear channel assessment parameters, RF settings, and advanced settings.

Basic Configuration

The basic EasyLink stack configuration includes address filtering, address size, and max data length. When these paramters are configured via SysConfig, they will take affect when the EasyLink_init() API is called.

Clear Channel Assessment (CCA) Configuration

The CCA configuration parameters are used when checking if a channel is clear of traffic before transmitting. The combination of RSSI threshold and channel idle time define what is considered a “clear” channel. The max and min backoff window, backoff time units, and random number generation function define the behavior when the channel is sniffed and found to be busy. The CCA configuration parameters take affect when using the EasyLink_transmitCcaAsync() API.

Advanced Configuration

The advanced configuration parameters require in-depth knowledge of the EasyLink APIs. For more information on these configuration parameters please see the EasyLink_CtrlOption enumeration for use with the EasyLink_setStrl() API. When the advanced configuration parameters are configured via SysConfig, they take affect when the EasyLink_init() API is called with the exception of the Asynchronous Rx Timeout (ms) and the Test Mode Whitening paramters. These require the use of the EasyLink_receiveAsync() and EasyLink_setCtrl() APIs respectively.

RF Configuration

The RF configuration of the EasyLink stack includes setup of both the RF driver and any PHYs the application needs to support. The RF Driver provides access to the radio core and offers a high-level interface for command execution that is utilized by the EasyLink APIs. Configuration of the PHY settings includes selecting the default PHY that will be used when the EasyLink_init() API is called as well as any additional supported PHYs. As each PHY is added to the configuraiton a Radio Configuration module will provide the ability to customize settings such as frequency, power, etc. All the RF configuration parameters take affect when calling the EasyLink_init() API.

Responsibilities of the Application

Several EasyLink stack parameters configured in SysConfig require the application to use specific EasyLink APIs to take affect. The following table shows which parameters that require the use of these APIs in the application.

| Configuration Parameter(s)          | EasyLink API needed to take Affect                 |
|-------------------------------------|----------------------------------------------------|
| All parameters                      | EasyLink_init()                                    |
| Clear Channel Assessment Parameters | EasyLink_transmitCcaAsync()                        |
| Asynchronous Rx Timeout (ms)        | EasyLink_receiveAsync()                            |
| Test Mode Whitening                 | EasyLink_setCtrl()                                 |

Provided SysConfig Files

The .syscfg file provided with an EasyLink stack example project has been configured and tested with that project. Changes to the .syscfg file can and will alter the behavior of the example. Some stack parameters configured in SysConfig will require the use of specific EasyLink APIs to take affect. Please refer to the Responsibilities of the Application section of this document for further information on which configuration parameters require the use of specifc APIs.