Tag Archives: arduino

How to tell if PL-2303HX ( PL-2303 ) is 3.3v or 5v

If you have a USB adapter and would like to use it when working with Arduino or Raspberry Pi you may wonder if it is safe to use with a 3v3 system. Purchasing these on eBay can be cheaper than buying from someplace like Adafruit but the listings often have no documentation on if the chip can be used with 3.3v devices. You can measure some of the pins to make your own determination. The unit I was working with several pins labeled: I measured voltage between the GND pin and the TX pin which gave around 1.8 – 2.5V without any data being transmitted. When I sent data to the device the voltages went intermittently to around 3.3 volts or maybe 3.4 volts. But I wanted to make sure that the chip was actually setup for 3.3v and so I found the datasheet for the PL-2303HX Make sure to get the correct datasheet for the chip you have – some of the chips are slightly different, like the HXD version. On page 11 of that datasheet it showed the pinout diagram – notice the small circle indicating “pin 1” which should correspond to the small dot on the actual chip: Pin 4 is labeled VDD_325 and the note says: RS232 VDD. The power pin for the serial port signals. When the serial port is 3.3V, this should be 3.3V. When the serial port is 2.5V, this should be 2.5V. The range can be from 1.8V~3.3V. Use this information at … Continue reading

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Review: X10 Home Automation with Arduino

This is a re-post of ┬áthis blog posting since it appears to be a 404. —- My current project revolves around using the Arduino and the X10 home automation protocol and hardware. The gist of what I am doing with this project is using the Parallax RFID (found here) tag to identify me and then use X10 protocol/hardware (Part# 1134B from SmartHomes via Amazon) to automate my home. Below is the wiring diagram. In this example, I control 1 device (on X10 circuit A, device 1). I initally turn the device off. When the RFID tag I am looking for is read, I turn the lights on. Next time that tag is read, I turn the lights off. I acknowledge various changes by providing feedback to the user via blinking LEDs and serial comms to the PC. I use the free SSH/telnet client PuTTY, found here. Now, for the code… ——————————————– #include x10.h #include x10constants.h // RFID reader variables #define TAG_LEN 12 char tag[12] = {‘0’, ‘F’, ‘0’, ‘3’, ‘0’, ‘3’, ‘7’, ‘1’, ‘8’, ‘5’}; char code[12]; int bytesread = 0; int ledPin = 13; // Connect LED to pin 13 int rfidPin = 2; // RFID enable pin connected to digital pin 2 int val=0; // X10 Control unit variables int zcPin = 9; int dataPin = 8; int repeat = 1; boolean LightsOn = false; // Declare and instance of an X10 control module x10 myHouse = x10(zcPin, dataPin); // 9 is 0xing pin; 8 is data pin … Continue reading

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