AVR465 datasheet(22/40 Pages) ATMEL

22 / 40 page

AVR465

2566A-AVR-07/04

For stand-alone operation, the meter is simply connected to the mains wires as

illustrated in the schematic. The meter automatically starts to measure power and

stores energy consumption data in the display counter. Note that the meter needs to

be calibrated before reliable measurement data can be expected.

For programming, calibration and testing purposes the meter needs to be temporarily

connected to external hardware, such as a computer or a microcontroller. The

external hardware writes the firmware into the FLASH memory of the meter MCU. It

then assesses the accuracy of the meter and writes calibration data into the

EEPROM of the MCU. The meter is ready to run in stand-alone mode after

programming and calibration has completed successfully.

A general illustration on how to connect the meter for programming, calibration and

metering is shown in Figure 12. Please note that this is a generalized block schematic

and does not include all recommended safety precautions.

Figure 12.

Connecting the Meter to External Hardware.

465

STK500,

AVRISP,

JTAGICE mkII,

or similar

SIGNAL

GENERATOR

HIGH

VOLTAGE

& CURRENT

USART

ISP

STK500,

or similar

Computer

running

AVR Studio

and

terminal

RS-232

It is recommended to create a galvanic isolation barrier between the mains-coupled

meter and the other hardware. This can be done using optocouplers at the ISP and

USART interface or at the RS-232 interface. Optocoupling both ISP and USART

makes the STK500 and debugger “safe”, but requires many optocouplers.

Alternatively, creating the galvanic barrier at the RS-232 interfaces requires less

optocouplers but makes all devices except the PC hazardous.

Another alternative is to use an isolation transformer to create a floating front-end,

which can then be bolted to the same ground as the rest of the electronics.

The meter AVR is programmed via the In-System Programming (ISP) interface, which

means the device does not need to be removed for programming. The ISP connector

(J1, see schematic) is connected to a programmer (STK500, ATAVRISP, or similar)

or a debugger (ATJTAGICEmkII, or similar). Software such as AVR Studio can then

be used for programming FLASH and EEPROM of the target AVR.

The meter constantly sends measurement data via the asynchronous interface. To

read measurement data (also during calibration), the asynchronous interface must be

connected. The asynchronous connector (J2, see schematic) is wired to a

microcontroller directly or to a computer via a RS-232 buffer. The asynchronous

interface cannot be wired to a RS-232 port directly, since it is not buffered.

A RS-232 buffer is readily found on the STK500. Connect the asynchronous interface

of the meter to STK500 pins labeled RS232 SPARE. Then connect the STK500 D-

connector labeled RS232 SPARE to the serial port of the computer. Use a terminal

software of choice to read data from the serial port.

A general illustration on how to connect the meter for programming, calibration and

metering is shown in Figure 13. Also shown in the figure is a recommended optical

isolation board.

Hardware Set-Up

Warning: Galvanic Isolation

Programming

Calibration & Metering

AVR465 Datasheet(PDF) 22 Page - ATMEL Corporation

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