AN3985 datasheet(18/105 Pages) STMICROELECTRONICS

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CR95HF low level layer

AN3985

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Doc ID 022255 Rev 2

CR95HF_ProtocolSelect function

This function sends a Protocol Select command to the CR95HF. It selects the RF

communication protocol, configures RF parameters, and switches the RF field on.To set up

communications with a contactless tag, the Protocol Select command shall be sent to the

CR95HF before the SendRecv command.

For more detail concerning this parameter, please refer to the CR95HF datasheet.

Table 14.

CR95HF_ProtocolSelect function description

Prototype

u8 CR95HF_ProtocolSelect (const u8 Protocol, const u8

ParametersLength,const u8* Parameters,

CR95HF_Protocol_Config* Protocol_Settings);

Input parameter(1)

The input parameter settings depend on the selected protocol. This application note applies to ISO/IEC

15693 products.

Protocol: RF protocol selected

ParametersLength: length of any parameters attached

Parameters: any parameters to be attached for different protocols

Output parameter

Protocol_Settings: structure at the end of the command containing the

last protocol selected and its parameters

Return parameter

CR95HF_SUCCESS_CODE: The command is successful.

CR95HF_ERROR_INVALID_PROTOCOL: The protocol selected is invalid.

CR95HF_ERROR_INVALID_CMD_LENGTH: The command length is

invalid.

CR95HF_ERROR_CODE: The command failed.

Table 15.

Input parameters settings for ISO/IEC 15693 protocol

Parameter name

Byte

Bit

Value

Example

Command code

0x02

02020126

Length

0x02

Protocol

0x01: ISO/IEC 15693 protocol

Parameter

7:6

RFU

5:4

0b00: 26 kbps

0b01: 52 kbps

0b10: 6 kbps

0b11: RFU

0b0: ensure a 312 µs delay

0b1: wait for SOF

0b0: 100% modulation

0b1: 10% modulation

0b0: single subcarrier

0b1: single subcarrier

0b0: don’t append CRC

0b1: append CRC (1)

It is recommended to set the append CRC bit (see Chapter 5.3.4: CRC16 management)

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