What is it? Shield used to connect a microcontroller and a host computer (with USB) to a full duplex RS-422 serial line (RX and TX pairs) and a half duplex management line (DTR pair) through CAT5 c...Read More…
Shield used to connect a microcontroller and a host computer (with USB) to a full duplex RS-422 serial line (RX and TX pairs) and a half duplex management line (DTR pair) through CAT5 cable.
So my Ubuntu desktop could access the multidrop serial line with the RPUno and upload firmware.
The transceivers have fail-safe biasing (e.g. the logic state is defined above -50mV) so they can be disabled when the UART TX is high and all receivers will see a high. Sparkfun has an RS485 shield that does this for a single pair. When RS-422 has an automatic enable it is controlled like RS-232 (almost), e.g. the core control software for the UART does not need to know about the transceivers (since they are not enabled by the core). The only concern is to make sure multiple devices don't answer at the same time. A big deal for myself is that avrdude can upload firmware when I configure a point to point mode.
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United States Postal Service: Priority Mail
Priority Mail Small Flat Rate Box will hold two RPUno, or two shields (RPUftdi or RPUadpt) and an RPUno.
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I am working on what may be thought of as a SCADA system for the garden and workshop. I prefer WiFi to be on the SBC (Pi Zero) or host computer that I can then connect to a multi-drop serial for interfacing the somewhat industrialized microcontrollers. To bootload, I have set up the multi-drop serial so it has a full duplex connection between the host and microcontroller and a half-duplex connection that can manage what is (or is not) connected to the full-duplex bus. This is done with a specific favor (Intersil) of RS-485 transceivers.