Multiple RS485 ports on a single BBB

I need to use a Beaglebone Black as both RS485 master and slave at the same time, so I need two RS485 ports available. I’m wondering whether the “ BeagleBone Comms Cape” which has a single RS485 port is stackable, or if there is a Cape available which has two ports.

You might be better just wiring up a couple of RS485 drivers on a proto-cape.

Sparkfun claims this is out of stock and discontinued. Here they say it’s still available. Old inventory maybe?

BeagleBone Black Proto Cape - RobotShop

However if it’s discontinued I’m not surprised. Seems to be the future of the BBB anyway.

You can program the EEPROM to point to a custom DTS file which then gets uboot to load it when the cape is plugged in. The DTS would reserve the appropriate Serial Port pins for you along with the pins required to switch from Rx to Tx for each driver.

Without the EEPROM

And now you’d have to add the appropriate link to the DTS file in uEnv.txt.



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I’ve considered using TTL UART to RS485 converters, would those (or something similar) be usable on a proto-cape? Sorry if its a stupid question, but I’m new to Beagle development.

This is the RS485 side of the logic supply RS485/RS232/CAN cape. Instead of the MAX485 you can also use the SN75176

I’ve also attached the cape-CBB-Serial-r01.dts file which you’d have to modify to remove the CAN and then as in that example use GPIO1_16 as one RS485 Tx enable and GPIO2_0 as the other RS485 TX enable.

After that it’s just software to enable the tx, wait a short time for the bus to turn around and then send. Then wait one character time before releasing the transmit.




cape-CBB-Serial-r01.dts (3.1 KB)

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