rfEasyLinkRx Example

Example Summary

Example includes the EasyLink API and uses it to configure the RF driver to RX packets. This project should be run in conjunction with the rfEasyLinkTx project.

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

Peripherals Exercised

Board_PIN_LED1 - Indicates an abort which is expected to happen 300 ms after RX has been scheduled
Board_PIN_LED2 - Indicates that a packet has been received Board_PIN_LED1 & Board_PIN_LED2 indicate an error
Board_GPTIMER0A - Used to timeout the receive operation if it runs over 300ms in the no-RTOS asynchronous implementation

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

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>.

Board Specific Settings

The default frequency is:
- 433.92 MHz for the CC1350-LAUNCHXL-433
- 433.92/490 MHz for the CC1352P-4-LAUNCHXL
- 2440 MHz on the CC2640R2-LAUNXHL
- 868.0 MHz for other launchpads 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
On the CC1352P1 the high PA is enabled (high output power) for all Sub-1 GHz modes by default.
On the CC1352P-2 the high PA operation for Sub-1 GHz modes is not supported
On the CC1352P-4 the high PA is enabled (high output power) for all Sub-1 GHz modes by default.
- The center frequency for 2-GFSK is set to 490 MHz
- CAUTION: The center frequency for SimpleLink long range (SLR) is set to 433.92 MHz, but the high output power violates the maximum power output requirement for this band
The CC2640R2 is setup to run all proprietary physical modes at a center frequency of 2440 MHz, at a data rate of 250 Kbps

Example Usage

Run the example. Board_PIN_LED2 will toggle indicating a packet has been received. Board_PIN_LED1 will toggle indicating an abort, which is expected to happen if a packet is not received within 300 ms of the RX being scheduled. Board_PIN_LED1 and Board_PIN_LED2 indicates an error (not expected to happen under normal conditions, but may occur if there is some interference).

After running this application you should start the rfEasyLinkTx on a second board to transmit packets. Until the rfEasyLinkTx has been started the receiver will be continuously RX.

Application Design Details

This example shows how to use the EasyLink API to access the RF drive, set the frequency and receive packets. The board will blink LED2 when a packet has been received. When a second board is running rfEasyLinkTx example then the expected behavior is that Board_PIN_LED2 will blink every 100 ms 10 times, the TX will then wait for 300 ms before transmitting the next packets and if RFEASYLINKRX_ASYNC is defined (as it is by default) then this will cause the rfEasyLinkRx example to timeout and exercise the EasyLink_abort API. When an RX has been aborted Board_PIN_LED1 should toggle. The rfEasyLinkTx board will then transmit another burst of packets and Board_PIN_LED2 should blink another 10 times and the cycle should repeat.

If RFEASYLINKRX_ADDR_FILTER is defined (as it is by default) then the RX address filter will be enabled for address 0xaa. This will cause the rfEasyLinkRx to only accept packets with a destination address of 0xaa, which the rfEasyLinkTx example transmits. When using the rfEasyLinkTx example there will be no difference in behavior when defining/undefining RFEASYLINKRX_ADDR_FILTER as the rfEasyLinkTx example will use a destination address of 0xaa. However, if transmitting from another source like SmartRF Studio and not using an address of 0xaa, then defining RFEASYLINKRX_ADDR_FILTER will result in packets not being received.

A single task, “rfEasyLinkRxFnx”, configures the RF driver through the EasyLink API 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 canceled 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 canceled 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.

No-RTOS Implementation

The No-RTOS implementation uses a general purpose timer to timeout the receive operation, for the asynchronous case, if it exceeds 300ms.

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 acknowledgments.

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.