I decided to use one of the 2-digit 7-segment LED displays I had in my parts drawer (a KEM-5621-BSR Common Anode 7-Segment LED Display, specifically ) and the Arduino Library “SevSeg” to drive it. Let’s go back in time and do the same thing! We still need some way to show that the radar is working. #Critical ops hack script with radar serialSubsequently, the example code above will not show data over the Serial Monitor. (The photo above demonstrates this approach.)īE AWARE: As mentioned in Step 2’s introduction, Arduino Uno’s TX/RX lines share hardware lines with USB data, so using TX/RX and USB at the same time does not work. You will want to wire the Arduino TX pin 1 (interior) to MOSI (interior hole next to arduino pin 11) in order to send API commands from the Arduino to the OPS241.Īlternatively, you don’t need to use a shield.just wire the pins directly to your Arduino’s TX and RX. You may have observed that MISO (OPS241 transmit to output) is crossed over to Arduino’s RX (receive) because the OPS241 wants its output to be received at the Arduino’s receive pin. Fortunately, Arduino pins RX (0) and TX (1) are! Make sure there is no header for plugging in pins 11 and 12 into the shield sockets, then solder in a wire between MISO (the interior hole next to arduino pin 12) and the lowest interior, hole next to the pin at RX. While the OPS24x can support very high baud rates over MOSI and MISO, the Arduino pins 11 and 12 are not suitable for high speed communication. OPS241 with 2 jumper wire brought down to TX and RX Be aware that if the Radar is running and communicating over TX/RX, this will also impact your ability to flash a new program out to your Arduino. If that is important to your, you might want to consider an Arduino with more UART support, like a Mega. However, the Arduino Uno ties the TX and RX lines to USB lines, so you will not be able to use the USB interface and read radar data at the same time. You are going to be more pleased with the communications reliability if you use the Arduino hardware serial pins 0 and 1. If so, you just learned about some of the characteristics of the SoftwareSerial approach. Perhaps you noticed some serial communication character glitches when you looked at the data stream. Step 2: Improved Communications with TX and RX (Have you ever tried to wave your hand at 88 mph? Great Scott! It's not easy!)Ĭongratulations, you now have a radar-based speed detector!! "UC" will send speeds in centimeters-per-second, useful if you want to see decently large numbers. For instance, ‘?’ asks the sensor to return some basic information, or “US” to request the units be miles per hour. If you move your hand towards or away from the antenna on the OPS24x (the gold squares), you will see the numbers change! □ That is the speed of your hand in meters per second! You are even able to send API calls to the OmniPreSense radar module. Use the Arduino IDE’s Serial Monitor (or a program that treats a USB as a serial port, like PuTTY or TeraTerm) to see the velocity data from the radar. set the data rate for the SoftwareSerial port SoftwareSerial ops241Serial(12, 11) // the OPS241 MISO->12 and MOSI->11 pins This merely copies bytes between the Serial output and the OPS241. It looks like the code below, but I changed the name of the Serial object. You simply need to assign the correct pins and take out the unnecessary “Hello World” print line. The SoftwareSerial page at provides a great start for this step. If you use an OPS242, you should use an Arduino that runs at 3.3 V. If you have an OPS241 without shield headers installed (or an OPS 242, which is not a shield), you can skip to Step 2, where we talk about using jumper wires. The OPS241 has UART pins exposed to Arduino digital pins 11 (labeled MOSI- I try to remember it as Output-to-others-Input) and 12 (labeled MISO- Input-from-others-Output) In case you worry about such thing, the OPS241 also has voltage level shifters that brings Arduino Uno’s 5V down to the 3.3 V required by the ARM chip on the OPS24x. Plugging the OPS241 as a shield into the Arduino Uno is the simplest starting point.
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