ib technology

8

Host Driver software

Communication with the MicroRWD module is via the TTL level RS232 interface (9600

baud, 8 bit, 1 stop bit, no parity) and uses the CTS line for hardware handshaking. The

Windows applications (supplied with the Evaluation kit) can be used to communicate with the

module or the user can write their own application on a PC or a microcontroller. Please note

that the host software must be able to handle the three distinct polling rates (different periods

between CTS pulses). The following basic communication algorithm can be used:-

Typical host computer “pseudo” driver code

if (Green LED ON (pin 2 = 0))

// Optional check for valid tag in field

{

if (CTS = 0)

// Wait for CTS = 0 (RWD ready to receive command / data)

{

// CTS times out after 6ms so command and all parameters must be sent with

// no gaps otherwise CTS times out and goes HIGH.

// For example, send READ TAG command (with dummy page no.) (0x52 0x00)

SEND_BYTE( 0x52);

// Send command

SEND_BYTE( 0x00);

// Send argument 1

// RWD sets CTS = 1 after last parameter received. RWD module processes

// command, turns on RF for short period, waits then sends reply.

GET_REPLY( );

// Get Acknowledge byte + data

// Response to READ command is 0xC0 (no tag) or 0xD6 + five bytes of DATA.

}

}

Command Protocol

The following commands are supported. The corresponding acknowledge code should be read

back by the host and decoded to confirm that the command was received and actioned

correctly. The serial bit protocol is 9600 baud, 8 bits, 1 stop, no parity (lsb transmitted first).

The status flags returned in the Acknowledge byte are as follows:

b7 b6 b5 b4 b3 b2 b1 b0

1

1

1

1

1 1 1 1

|

|

|

|

|

EEPROM error (Internal EEPROM write error)

|

|

|

| Tag OK (Tag identity code matched to list and authentication successful)

|

|

| Rx OK (Tag communications and acknowledgement OK)

|

|

RS232 error (Host serial communications error)

|

RELAY (OP2, OP3) Enabled flag

HTRC (or Antenna fault) error flag

Note that bits 6 and 7 are fixed 1’s so that an acknowledge code of D6 (Hex) would generally indicate no errors

with a matched (or authorised) Tag present.

Note also that only the relevant flags are set after each command as indicated in the following specification.