PCA9600 Differential I2C Long Cable Extender with Boost Convertor
This module is designed to enable long-range I2C communications which extend the cable length from several meters to 300 meters. It is ideal for applications that need to run over long wires such as the CAT5E Ethernet cable that is commonly used to make connections between rooms. The signals are transmitted via balanced transmission lines (twisted pairs) which greatly reduces noise and extends the range. NXP PCA9600 I2C bus extender IC is used as the main component of this module. The PCA9600 is designed to isolate I²C-bus capacitance, allowing long buses to be driven in point-to-point or multidrop applications. It can operate at speed up to at least 1 MHz.
- The BOOST version has an onboard boost converter that can feed 12V/24V (configurable) power to the VBUS.
- The BUCK version has an onboard buck converter that can take power from the VBUS and buck it down to 5V. This can be used to power the BUCK module itself and also the connected device(s).
The VBUS wires could provide power to the whole system. This eliminates the need to power every remote module and device separately.
- Bidirectional data transfer of I2C-bus signals
- 100 kHz operation on 300 meters of wire
- 1 MHz operation on 20 meters of wire
- On-board boost converter (12/24V output)
- Flexible pull-up voltage
- Multidrop connection
The picture below shows the waveform of SCL and SDA when the sensor is directly wired to Arduino via a 15cm length cable. CH1(yellow) is SCL and CH2(blue) is SDA.
Here comes the SCL waveform when connecting the sensor to Arduino via 300m length twisted pair cable.
It could be seen from the picture above that the stray capacitance of the cable has seriously deformed the SCL waveform at both local(CH1) and remote(CH2) end.
Here comes the SCL waveform shows the performance of our differential I2C extender with Arduino, HDC1050, and 300m twisted pair cable.
and if we give it a closer look, we can actually see the propagation delay of the SCL signal.
It could be read from the cursors in the picture the propagation delay of the SCL is about 1.76us. The propagation delay of the twisted pair cable is 4.8-5.3ns/m. Given the length of the cable which is 300m, the propagation delay should be 1.4-1.6us. There is also some delay between the differential transceivers and some measure errors. So the 1.76us reading is quite reasonable.
In the Package
- A fully assembled and tested differential I2C extender
If you need an adapter to ease the wiring to a CAT5E cable, please take a look at the Differential I2C Extender with RJ45 adapter
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