ST M24LR64-R温度数据无线采集解决方案~*

发布时间：2011-9-14 11:12 发布者：1770309616

ST公司的 M24LR64-R是无线存储器，具有口令保护的64Kb EEPROM以及400kHz I2C串行总线和13.56MHz ISO 15693 RF协议的双接口的64Kb EEPROM，可实现智能手机的近场通信（NFC）.单电源1.8V-5.5V工作，64kb EEPROM分成I2C模式的8192B和RF模式的2048x32b，无接触接口和ISO 15693与ISO 18000-3 mode 1兼容，载波频率13.56 MHz ±7k Hz，广泛用于工业和消费类电子产品.本文介绍了M24LR64-R 主要特性,功能方框图,数据采集器中STM8L101K3/M24LR64-R/STTS75的通信方框图,电路图和温度数据采集器元件表.

Developing your M24LR64-R datalogger application for temperature acquisition

The M24LR64-R device is a dual-interface, electrically erasable programmable memory(EEPROM). It features an I2C interface and can be operated from a VCC power supply. It is also a contactless memory powered by the received carrier electromagnetic wave. The M24LR64-R is organized as 8192 × 8 bits in the I2C mode and as 2048 × 32 bits in the ISO 15693 and ISO 18000-3 mode 1 RF mode.

I2C uses a two-wire serial interface, comprising a bidirectional data line and a clock line. The devices carry a built-in 4-bit device type identifier code (1010) in accordance with the I2C bus definition.

The device behaves as a slave in the I2C protocol, with all memory operations synchronized by the serial clock. Read and Write operations are initiated by a Start condition, generated by the bus master. The Start condition is followed by a device select code and Read/Write bit (RW), terminated by an acknowledge bit.

When writing data to the memory, the device inserts an acknowledge bit during the 9th bit time, following the bus master’s 8-bit transmission. When data is read by the bus master, the bus master acknowledges the receipt of the data byte in the same way. Data transfers are terminated by a Stop condition after an Ack for Write, and after a NoAck for Read.

In the ISO15693/ISO18000-3 mode 1 RF mode, the M24LR64-R is accessed via the 13.56 MHz carrier electromagnetic wave on which incoming data are demodulated from the received signal amplitude modulation (ASK: amplitude shift keying). The received ASK wave is 10% or 100% modulated with a data rate of 1.6 Kbit/s using the 1/256 pulse coding mode or a data rate of 26 Kbit/s using the 1/4 pulse coding mode.

Outgoing data are generated by the M24LR64-R load variation using Manchester coding with one or two subcarrier frequencies at 423 kHz and 484 kHz. Data are transferred from the M24LR64-R at 6.6 Kbit/s in low data rate mode and 26 Kbit/s high data rate mode. The M24LR64-R supports the 53 Kbit/s in high data rate mode in one subcarrier frequency at 423 kHz.

The M24LR64-R follows the ISO 15693 and ISO 18000-3 mode 1 recommendation for radio-frequency power and signal interface.

M24LR64-R 主要特性：

I2C interface

■ Two-wire I2C serial interface supports 400 kHz protocol

■ Single supply voltage:

– 1.8 V to 5.5 V

■ Byte and Page Write (up to 4 bytes)

■ Random and Sequential Read modes

■ Self-timed programming cycle

■ Automatic address incrementing

■ Enhanced ESD/latch-up protection

Contactless interface

■ ISO 15693 and ISO 18000-3 mode 1 compatible

■ 13.56 MHz ±7k Hz carrier frequency

■ To tag: 10% or 100% ASK modulation using 1/4 (26 Kbit/s) or 1/256 (1.6 Kbit/s) pulse position coding

■ From tag: load modulation using Manchester coding with 423 kHz and 484 kHz subcarriers in low (6.6 kbit/s) or high (26 kbit/s) data rate mode. Supports the 53 kbit/s data rate with Fast commands

■ Internal tuning capacitance: 27.5 pF

■ 64-bit unique identifier (UID)

■ Read Block & Write (32-bit Blocks)

Memory

■ 64 Kbit EEPROM organized into:

– 8192 bytes in I2C mode

– 2048 blocks of 32 bits in RF mode

■ Write time

– I2C: 5 ms (Max.)

– RF: 5.75 ms including the internal Verify time

■ More than 1 Million write cycles

■ Multiple password protection in RF mode

■ Single password protection in I2C mode

■ More than 40-year data retention

■ Package

– ECOPACK2® (RoHS compliant and Halogen-free)

图1.M24LR64-R功能方框图

Developing your M24LR64-R datalogger application for temperature acquisition

The M24LR64-R is a Dual interface EEPROM. Since it has both an 13.56 MHz ISO 15693 RFID and a 400-kHz I2C interface, the device is a good solution for RF-enabled sensors for which ST has developed a reference design. One of the main benefits brought by the M24LR64-R is that the sensor data can be accessed in read and write mode without consuming any on-board power.

This application note presents a practical useful application for the M24LR64-R datalogger.

It describes an autonomous battery-powered datalogger able to record and store 64 Kbits of temperature data using the M24LR64-R Dual interface EEPROM (I2C and RF). The datalogger microcontroller is an STM8L101K3. It communicates with the M24LR64-R using its serial interface and controls an STTS75 digital temperature sensor. An on-board demonstration firmware,

the M24LR64-R_Datalogger_application_firmware, stored in the STM8L101K3 memory selects and controls the temperature acquisition through a RFID reader connected by a USB cable to a PC.

The application is delivered with a PC software, the M24LR64- R_Datalogger_application_software, to configure and control the datalogger, as well as download and display the temperature values.

ST provides all the resources required to develop your own datalogger application and PC software:

● Source files of the data logger firmware (M24LR64-R_Datalogger_application_firmware): they allow implementing I2C communications between the M24LR64-R, the STTS75, and the STM8L101K3.

● Source files of the PC software (M24LR64-R_Datalogger_application_software): they control RF communications between the M24LR64-R and an RFID reader.Basic information about the M24LR64-R, STTS75, and STM8L101K3 component characteristics, as well as a description of the algorithms for the datalogger firmware and PC software are provided in this document.