SRF485 ultrasonic ranger and Arduino Uno

Using Arduino Sensors
1

Hello,

I recently bought an SRF485 ultrasonic ranger which I want to interface with an Arduino Uno.
I went through the technical specifications, but I am not sure exactly how to send commands to the SRF485 via the Arduino.

  1. How do I send a break ?
  2. Are digital pins 0,1,2 used to send/receive data to the SRF485 module?
  3. If so, how would I send the commands using digitalWrite/digitalRead?
    I would imagine they need to be sent serially, not with digital pins.
  4. I connected A to RS485+ and B to RS485-, is that right?

Thank you.

2

How do I send a break ?

Break - is defined as a continuous low in excess of 22 bit periods, followed by a high of 2 bit periods. Each bit is 26uS at 38400 baud, so 22 * 26uS = 572uS, it's ok to be longer.

Why chose such an interface, when simpler ones with less rigorous specs are available?

3

I want to try this interface because of the capability of placing many sensors on one bus.

4

charalambos:
I want to try this interface because of the capability of placing many sensors on one bus.

Good point, RS485 can support multiple devices on one bus. But, with the high cost per sensor, it seems it would be cheaper to go with multiple SRF05's and just use hardware with more pins available. Keep in mind that the SR04 and SRF05 can be wired to use only one pin each when used with the NewPing library. Also, they are extremely cheap, like 1/10th the price of a RS485.

Tim

5

Or even I2C like an SRF02 for medium length cables.

6

Thanks everyone. So I guess nobody ever tried SRF485 with Arduino?
Also note I am using DFRobot's expansion board V5.0

7

charalambos:
Thanks everyone. So I guess nobody ever tried SRF485 with Arduino?
Also note I am using DFRobot's expansion board V5.0

Just not popular I'm sure due to the high cost. SR04 sensors can be purchased for <$3 on eBay. And if your project will use multiple sensors, the difference in price is even greater. How many sensors do you plan on having? How many pins do you have available?

Tim

8

Not sure how many sensors yet. I just want to interface two for the time being for the sake of testing them.

9

Hello again,

Just making a note that I want to use the SRF485 not only because of the capability of placing many sensors in one bus, but also because of the capability of driving 3 LEDs at once.

10

charalambos:
Hello again,

Just making a note that I want to use the SRF485 not only because of the capability of placing many sensors in one bus, but also because of the capability of driving 3 LEDs at once.

You can drive 3 LEDs with any ultrasonic sensor. There's nothing magic about the SRF485 that allows you to use more LEDs.

Tim