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protocol_PX-100_2_70.md

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PX-100 ELECTRONIC LOAD

This document applies to PX-100 Electronic load version 2.70 with rs-232 TTL serial interface.

Electrical diagram

Any USB TTL Serial adapter should do. Both 3.3V and 5V IO levels work. I used FT232 adapter from A.

LOAD RS-232 TTL adapter
GND GND
TXD RXD
RXD TXD

Connection settings

Electronic load uses 9600 baud 8N1 (8 bits, no parity, 1 stop bit) configuration with no flow control.

Binary protocol

Electronic load uses a binary protocol with 7-bytes control frames sent by host and either 1 or 7 bytes response frames. All other data is ignored, until the next command is received. No line end characters is sent or expected.

The control frame looks like:

  0xB1 0xB2 CMD D1 D2 0xB6

with 2 header bytes 0xB1 0xB2 and a trailing byte 0xB6

Data format of control commands differs from the query commands.

Control commands

Control commands start with 0x0* and the unit responds with 1 byte 0x6F

First data byte carries the integer part, second data byte carries a fraction * 100

So 1.23 V will be tranmitted as 0x01 0x17 hexadecimal.

Command Data Description
0x01 0x0100 - ON \ 0x0000 OFF Enable or disable the load
0x02 D1.D2 Set current
0x03 D1.D2 Set cutoff voltage
0x04 16-bit unsigned integer Set timeout in seconds
0x05 0x0000 Reset counters

Query commands

Query commands start with 0x1* and the unit responds with 7 bytes:

  0xCA 0xCB D1 D2 D3 0xCE 0xCF

Request data bytes should be send as 0x00.

Response data format varies.

Command Response Data Description
0x10 0x000000 OFF 0x000001 ON Load enabled ?
0x11 24-bit integer Voltage reading, mV
0x12 24-bit integer Current reading, mA
0x13 D1 hours, D2 minutes, D3 seconds Elapsed or remaining time
0x14 24-bit integer Capacity, mAH
0x15 24-bit integer Capacity, mWH
0x16 24-bit integer Mosfet temperature, °C
0x17 24-bit integer Current setting, AH * 100, 1.23A would be sent as 123
0x18 24-bit integer Cutoff voltage setting, V*100, 3.21V will be sent as 321
0x19 D1 hours, D2 minutes, D3 seconds Timer setting