IRIG Encoding External Data Tech Note 409 A Measurement Specialties 65210 Series Inertial Measurement System with built-in IRIG encoder can be used to IRIG encode data received on its RS485 serial line. To configure a 65210 Series System channel to IRIG encode external data, select the RCAL value as the channel’s input and set the channel filter to a high value (e.g. 10,000 Hz). Once configured, commands sent to set the channel’s RCAL value will cause the value to be included in the IRIG frames output by the 65210 Series System. 65210s allow up to16 bits of data to be encoded per sensor channel. Six steps are required to set an RCAL value: 1. Send a Listen Command to enable the 65210 Series System to process commands 2. Wait for the 65210 Series System to acknowledge processing of the Listen Command 3. Send the address of the RCAL value to be changed to the 65210 Series System 4. Wait for the 65210 Series System to acknowledge processing of the new address 5. Send the new RCAL value to the 65210 Series System 6. Wait for the 65210 Series System to acknowledge setting of the new RCAL value Multiple IRIG channels can be set in step 5 if they are contiguous. The example at the end of this Tech Note shows channels 12 through 16 being set with a single command. Steps 3 thru 6 can be repeated to encode additional values as long as they are not updated faster than the IRIG frame rate. To ensure data integrity, each message sent to and received from a 65210 System is framed with an 8 bit command header and a 16 bit CRC. The CRC16 is computed from the header and data and then appended to the message. ‘C’ code to compute a CRC16 can be found in Tech Note 410. Invalid messages received by a 65210 System are discarded and not acknowledged . • RCAL settings are typically located at addresses 0x0280 through 0x029f: Chn 1 2 3 4 Address 0x0280 0x0282 0x0284 0x0286 Chn Address 5 0x0288 6 0x028A 7 0x028C 8 0x028E Chn Address 9 0x0290 10 0x0292 11 0x0294 12 0x0296 Chn Address 13 0x0298 14 0x029A 15 0x029C 16 0x029E • Each 16 bit value is stored and sent high byte first (e.g. channel 0 high byte is at 0x0280 and the low byte is at 0x0281, 0x1234 is sent as 0x12, 0x34). • Addresses are sent as 32 bit addresses, low byte first (e.g. address 0x00000290 is sent as 0x90, 0x02, 0x00, 0x00). • CRCs are sent low byte first (e.g. 0x06C0 is sent as 0xC0, 0x06). TN 409: IRIG Encoding External Data precisionsensors.meas-spec.com 2236 N. Cleveland-Massillon Road Akron OH 44333 PH : 330-659-3312 7/24/2013 www.meas-spec.com Example IRIG Encoding Data Using 65210 Series System Channels 12 through 16 Step 1 Sent by Controller 0x18 0x01 <crc> <crc> Listen Device ID 1 (factory default ID) CRC Low CRC High 2 3 0x4C 0x96 0x02 0x00 0x00 <crc> <crc> 0xAD <data> <data> <data> <data> <data> <data> <data> <data> <data> <data> <crc> <crc> 6 TN 409: IRIG Encoding External Data precisionsensors.meas-spec.com 0x09 0xC0 0x06 Ack (listening) CRC Low CRC High 0x09 0xC0 0x06 Ack (new address set) CRC Low CRC High 0x09 0xC0 0x06 Ack (new values set) CRC Low CRC High Send 4 byte RCAL address Chn 12 address CRC Low CRC High 4 5 Reply from 65210 Series System Write 10 bytes of data Chn 12 High data byte Chn 12 Low data byte Chn 13 High data byte Chn 13 Low data byte Chn 14 High data byte Chn 14 Low data byte Chn 15 High data byte Chn 15 Low data byte Chn 16 High data byte Chn 16 Low data byte CRC Low CRC High 2236 N. Cleveland-Massillon Road Akron OH 44333 PH : 330-659-3312 7/24/2013 www.meas-spec.com