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I am not an expert and I'm sure that there are things that could be done much better on this design, so feedback is welcome! What's even better is that they're fairly inexpensive at around $3 each for low quantities. Twisted pairs in RS485 communication however adds immunity which is a much better way to fight noise. RS485 is the most versatile communication standard in the standard series defined by the EIA, as it performs well on all four points. RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. The Windows drivers are compatible with LabVIEW standard serial driver interface (NI VISA). Laying out these motor drivers can be very intimiating, but I was able to stick with it and get it working. R1401 is a pull-up resistor that keeps the motor turned off during power up. The bypass caps are close to their respective power pins and the ESD diodes are snuggled up next to the connectors. The bypass capacitors for VCP, 5VOUT, and VCCIO all need to be close to their respective pins. The RP2040 has two I2C peripherals but giving up two more of the limited GPIO pins wasn't an option.

C1405 and C1406 are for ESD suppression (more on that in a bit). Unterminated: This is the simplest system, but only works if both the data rate and length are low enough. Low capacitance cable becomes important when pushing line length and/or data rates to the maximum. As a rule of thumb, the speed in bit/s multiplied by the length in metres should not exceed 108. Thus a 50-meter cable should not signal faster than 2 Mbit/s. The termination resistor should be equal to the characteristic impedance of the cable. A conversation with a cable manufacturer can help to define the best available cable for your application. The varistors (RV1401, RV1402 protect against coil overvoltage that can be caused by hot plugging or loose connections. This signal is used for sensorless homing- the TMC2209 will pull this signal high when it detects a stall which can be used to detect when the gantry collides with its physical endstop. Last, but certainly not least, Starfish needs to control three NEMA-17 stepper motors to move the machine's gantry. Since I want Starfish to work with these feeders, it needs to be able to talk RS-485.

You can enter the data relating to the MQTT Broker you want to use; the name of the Topic to be used to control it and to read the periodic transmissions of the humidity percentage is shown. This is super useful since it can be used to detect errors when picking and placing components. All of the ESD-related components need to be located as close to the connector as possible. These drivers require quite a bit of support circuitry and some care must be taken when selecting components. Other reasons that some RS-232 ports were half-duplex: some very old UARTs may be half-duplex limiting the system, and some very old computers drove the RS-232 drivers directly from the processor without a UART. RS-232 typically has a transmit wire, receive wire and signal common wire. The Lumen's upcoming powered feeders will communicate using RS-485, a multidrop serial bus common in industrial applications. Since the driver and receiver are differential circuits, the input and output voltages are specified as differential, but these voltages are also referenced to a circuit common. The other two signals, RE and DE, RS485 standard enable the transceivers input and output respectively.

Isolated transceivers are available in IC packages, modules, and gateways. C1402, C1403, and C1404 are bypass capacitors for the various voltage supplies used by the driver. Some consider this to be inverting since a 0 is the highest voltage and a 1 is the lowest voltage. Digital logic usually uses the same convention (but not the same voltage) as the lamp example. Logic IC's don't output a precision voltage. But some device manufacturers match their A and B labels to the symbol (no inversion), and some match to the signaling waveform (inverted). Adding the biasing resistor to every device on the network can cause termination problems. This means that there can be 32 nodes capable to both transmit and receive. Finally there is confusion from the IC manufacturers. Many other IC manufacturers make a drop-in replacement for this IC, and many of them (such as the MAX483) use the same labeling. Since all the TMC2209s share the same UART bus, this is used to give each one a unique address so they can be individually addressed. However, I wasn't going to get away that easily- Starfish needs two sensors and the XGZP6857D unfortunately has a fixed I2C address so they can't share the same I2C bus.