![]() ![]() The simplest method is a frequency-shift keying FSK modulation, where we use 2 sine tones (e.g. The modulator-demodulator (modem) was necessary to transmit digital signals which need a huge bandwidth (see Fourier in ELEFU) over the telephone line witch had only 3.4 kHz of bandwidth. The standard was needed to connect electromechanical teletypewriters (or dumb computer terminals), called data terminal equipment ( DTE) to a data communication equipment ( DCE, also data circuit-terminating equipment) like a modem. The Recommended Standard 232 ( RS-232) was originally introduced in 1960 as telecommunication standard. The terms MARK and SPACE are still used in the RS-232 standard. Telegraph operators noticed that the sound the needle made when scratching the paper was enough to get the message ans so the drum was replaced by a speaker. With an electromagnet it was possible to lift the needle away from the paper creating a space. Morse's first system had a needle contacting a rotating drum of paper that made a continuous mark. Morse made a first practical fully serial binary system with his Morse Code (first only uppercase letters). Sometimes a little history helps to better understand why things are what they are. This will give us a basic knowledge that we can transfer to other protocols. We will try in this chapter to understand one protocol in depth. I believe it's possible to implement automatic direction control with a minimum of external circuitry, as described in this TI whitepaper.Song of this chapter: Gordon Lightfood > Summertime Dream > Protocol You might want to make some considerations about how to manage the DE/RE logic depending on your application. RS232 to RS485 should be pretty straightforward it is just a matter of hooking the UART sides of a RS232 and RS485 transceiver together. You'll almost certainly need to write your own handler to perform this framing logic. A good example of such a UART is on STM32 devices, but I believe this is a fairly common feature for UART peripherals to have. Most UART handlers are written to expect groupings of bytes with predefined size, and will become permanently misaligned if errors are injected (dropped bytes, etc.). I strongly recommend using a microcontroller which can detect when its UART rx line is idle, and to frame groups of bytes with a minimum of one bytes worth of idle/delay between them. You will want to implement a checksum or CRC to verify message integrity before issuing a slave reply. You can create a setup where slaves transmit replies to matching master messages. The master device will send addressed instructions to the slaves, which will be configured to always receive. Multidrop RS485 can be implemented with only a single pair of wires. How could I achieve such a configuration? What components are needed and what details should I take into consideration when trying to build this? What protocols are required to ensure communication between all the parts involved? Is there just a better and more straightforward way to make this work? My master controller (the Teknic ClearCore) only supports RS-232 serial communication, so I presume I will need some kind of converter to achieve long-distance multi-node communication. In turn, they should communicate through I2C with the LED drivers to dictate which LEDs will light up at any given time. ![]() I would like the microcontrollers to all run the same software, but their unique ID should be configurable (increase/decrease) through two buttons on the PCB hosting them. I am hence thinking of another possible solution, where my controller addresses a series of microcontrollers with configurable addresses (could be simple AVR processors?) on an RS-485 bus. The IS31F元265A supports 16 different slave addresses, but those need to be hardware-configured and are limited in number. For this specific application, I am tying the driver's outputs in groups of 3 to achieve the desired current. The aim is to individually address an array of 150 mA LEDs, driven by the IS31F元265A PWM driver. I am trying to figure out how to achieve the master-slave configuration shown below.
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