AutoDriver SPI over RS-485 Shield v2

After verifying that the AutoDriver v1 shield was sound, I made a few changes to improve its functionality and ease of use. The biggest change was the addition of a switching power supply that can accept anywhere from 6 to 60 volts. This will allow it to be powered directly from the same power supply used to drive the stepper motors and removes the need for a separate 5v supply. The second change was switching from a transistor to a single logic inverter to invert the chip select signal. During initial testing the transistor would not turn on or off quick enough to function properly, the single logic gate would guarantee the quick switching times needed. The final change was to reorganize the signals on the connector simplify connecting up the wiring between devices.

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AutoDriver Shield v2 schematic

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SPI over RS-485 Testing

Arduino communicating with AutoDriver via SPI over RS-485 with 100' loop of CAT5.

Arduino reading the status register from the AutoDriver via SPI over RS-485 with a 100′ loop of CAT5.

In my last post, SPI over long distances, I described a method of using RS-485 to run a SPI bus over long distances. To test this setup I created two prototype shields, an Arduino SPI over RS-485 shield and an AutoDriver shield. Because the standard Arduino only has a single SPI bus and I needed two, one acting as a master and another as a slave, I would need to find a way to simulate one. Continue reading

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