Electronics, PCB Design and PCB Layout Daycounter, Inc.
Engineering Services

Custom Firmware, Electronics Design, and PCB Layout

Electronics Design
Firmware Development
Software Development
Embedded Design
PCB Layout
Digital Signal Processing (DSP)
Reverse Engineering
Device Driver Development
Motor Controllers
Data Acquisition Systems
Palm OS Software
Windows CE Software
Pocket PC Software
Design for Manufacturing
Through Hole to Surface Mount (SMT) Conversion 
Microchip PIC Consultant
MSP430 Development
DSP56 Development
RoHs Redesign
Design for USB

Silver Board Contract Assembly


SDI-12 Bus Interface

See our other Circuits.

SDI-12 is a arcane protocol used in environmental sensing. It consists of 2 wires: data and ground and runs at 1200 baud.  The bus is bidirectional, and the logger is the master, and the sensors are slave devices on the bus.

It's not a very easy protocol to implement.  Fortunately, you can purchase translators from Vegetronix which all easy implementation of the SDI-12 protocol.  They have SDI-12 to RS232 translators and  SDI-12 to USB translators for computer interfaces, and also analog to SDI-12 translators to convert any sensor into an SDI-12 compliant device. 

This simple circuit interfaces a 3.3V microcontroller with a 1200 baud UART to the SDI-12 bus.  Q1 is a voltage translator which translates the 5V signal from the SDI bus to 3.3V.  The tristate buffer, also translates the 3.3V from the UART TX line to 5V, and allows the microcontroller to place the line in the high impedance state when not transmitting, but deasserting the DIR_OUT line.  




 SDI-12 Bus Interface Schematic
SDI-12 Bus Interface Schematic


Do you need help with an electronics design?  Daycounter provides contract electronics design services. Contact us to give you a quote on your electronics design project.


[Employment] [Downloads] [Articles] [Contact Us]

Salt Lake City, UT, USA

Disclaimer: Daycounter, Inc. doesn't guarantee the accuracy of any of it's content. Use at your own risk.

© Copyright 2016 Daycounter, Inc. All rights Reserved.

Soil Moisture Sensor Probe

Water Level Sensor