-------------------- Tech Support Tips/Troubleshooting/Common Issues --------------------

Example Hookup and Arduino Code

Try looking at this article to for a general connection using the RS485 protocol [ https://arduino-info.wikispaces.com/RS485-Modules ] and some Arduino Example code [ https://arduino-info.wikispaces.com/SoftwareSerialRS485Example ].

That has to be one of the most useless videos I've seen in a while. How many times are you going to say, "My guess is..."?

Hi everyone! I am confused about the 220Ohm -so called terminator- resistors as it is recommended to use a 120 Ohm resistor near to each node, is it the same resistor in the RS-485 line or is recommended by the IC Manufacturer? even though it is not mentioned in the datasheet of the IC. BTW , if I want to use this module with some Biasing and EMC protection(I have already lost one module and the Arduino board connected to the module) , how should I consider this resistor because all of the documents are general and based on 120 Ohm P.S. I am trying to send some data with low baud rate on an about 10-20 meter CAT6 cable.

Lots of Good Stuff about using RS-485 beyond the lab bench at...

http://store.chipkin.com/articles/rs485-rs485-cables-why-you-need-3-wires-for-2-two-wire-rs485

The schematic says that there is a 220 Ohm termination resistance between A and B. But when I look at the picture of the board it shows that there is actually a 1.2 kOhm resistor present. Is there any specific reason for this? As normally for RS485 a 120 Ohm termination resistance is used?

I have just bought this board and although it does what is says it uses 20mA?

I have the board connected to a 3.3V regulated power source as well as the RST line to hard wire to transmit mode. This appears to draw 20mA? Is that what counts as low power or I am I doing something stupid here?

Thanks in advance for any help.

I have two of these wired up to UARTs 4 & 5 on a Beaglebone Black. The UARTs are properly (and tested!) muxed in the overlay. So I have TXD, RXD and RTS connected to the equivalent pins on the BOB-10124's (TX-O, RX-I and RTS pins) along with the requisite +3.3V and GND.

The BOB-10124's are connected with about a foot of CAT5 cable, A-A, B-B and GND to GND. My application code is pretty simple.

For both UARTs, I open /dev/ttyO4/5 and set up the speed etc. (no RTS/CTS):

UART4: Simply reads from the UART, prints out what it gets

UART5: 1) RTS enabled with ioctl(TIOCMBIS) on bit TIOCM_RTS 2) Delay 25ms 3) Write message 4) Delay 100ms 5) RTS disabled with ioctl(TIOCMBIC) on bit TIOCM_RTS

However, I cannot get it to transfer anything (or at least the receiving module (UART4) doesn't receive anything). I do see the RTS LED go on, then off after a brief pause, so it looks like it's sending. I know the pins and UART config is correct because if I just cross the UART pins directly it works fine.

I've tried many combinations, enabling RTS/CTS in the ioctl(TCSETS) initial set up ... so far nothing has worked.

I have a Saleae Logic, but it's an old one and doesn't do RS-485 (it's limited to 0-5v and doesn't have any analog channels), maybe this is an excuse to buy a Logic-8 ...

Any thoughts?

Any chance of starting a repo for this product? We've made an improved version of this board now which doesn't require the RTS pin. The change makes use of the Max13487 chip which has a built in state machine to determine the Rx and Tx directions. No more struggling with getting the timing delays correct for the RTS triggering. We use the new board design to communicate reliably with industrial equipment such as HMIs and VSDs at anything up to 115200baud. We'd love to share the changes with you, but don't want to start our own repo as it would be better placed under your original design. Thanks in advance...

I am interested in the new board design using the Max13487. Will Sparkfun be carrying these soon? If not does anyone know where I can find one or find the design and parts? I've been messing around with the 485 breakout board now for about a month and it is extremely difficult to get reliable fast communication. At best so far I'm only able to get communication speed to about 1/3 as fast as it should be and I still have some errors. When I use a USB to 485 it works flawlessly, except I don't want to use USB for the finished product.

So, I'm new to RJ485 and, if I use this board, I will be using this board for all the nodes in my little network so I don't care if it is compatible with other boards and I don't care if it is full-duplex. What I need to understand is how to connect them all together and communicate.

There is a Network Topology diagram at the bottom of this page that makes it look like it is as simple as connecting all the R's and S's on a sort of 2-wire bus with a couple of resistors at the ends. The wikipedia page for RS-485 describes several different topologies. Master-Slave would suit my project the best (but isn't an absolute requirement), but then I read on this other page that master-slave requires 4 wires and full-duplex.

Regarding communication, is it just as simple as connecting them to the TX/RX of the UART on my Raspberry Pi and Arduino boards? What about voltage translation between 3.3v and 5v devices? I know they boards can handle both but will the network of them handle a mix of voltages coming from the devices?

So, can anyone help me sort this out. I don't want to buy the boards until I at least have a basic understanding of how to use them.

RTFM! I admit it was me being stupid, but it doesn't help that they've named the pins differently from the chip. I really didn't expect the breakout labeled "TX-O" to be connected to "Pin 1 – RO – Receiver Output".

Hi, could some one please help me with connecting this adapter to an arduino (pro micro 5V 16 MHz). Any help would be appreciated. Thanks

The SP3485 specifies the Vcc to be 3.3 V. Is it allowed to operate this component with a Vcc of 3.0 V.? There is no indication whether this is allowed or not.

I got a few of these for prototyping a home automation project, connecting a bunch of stuff over CAT-5 and RS-485. I notice that the blue pair (4&5) are connected to ground in the schematic of the breakout board, but PoE (on wikipedia anyway) says the blue pair are DC+ and the brown pair DC-.

Is the breakout board wired for a different standard, and if so, which one?

would this be a practical solution to increase the length of spi lines. i only need output. my theorey wa to place one of these on either side like so:

arduino -> spi -> rs485 -> [long cable run 100ft] -> rs485 -> spi -> ws2801

or something similar. is there a better solution?

thanks!

-matt

can someone tell me where can I find this in the Sparkfun Eagle libraries ???

Help please... Can someone please provide a schema on how to connect this boars?? I have in one side a device with RS485 that is sending out data (I just send out and I don't need to read) and I would like to connect few of this board and get a TTL out from them? I try few times but without good result... Thanks

I've been using this breakout for about a year now and it's been working pretty well. I've noticed from the beginning, that I need to have a delay of about 25 ms after I send serial data before I can bring the RTS line low otherwise the transmission gets corrupted or is not transmitted. This hasn't been a big issue yet, but for a recent project I am running two 485 lines from one Arduino Mega 2560. I am receiving commands on one 485 line from the host software and transmitting them if the address is correct (I have several Megas running). I am expecting a response on the second 485 line from the devices I am sending commands to. The issue is that the peripheral devices respond in ~20ms and sometimes I get it and sometimes I don't (based on the state of the RTS pin). I need to transmit these responses back to the host software.

I feel like I should need these delays in the program. I would assume that the arduino has completed the transmission before it moves on from a serial.write() command. Any ideas?

am trying to connect Sparkfun RS485 breakout to Xbee Pro modem. Since the RS485 breakout uses the SP3485 RS-485 transceiver IC which has its RTS pin to control the data flow I assumed that this signal should be obtained from the Xbee RTS (DIO6), or CTS (DIO7). Although both IOs where configured as RTS and CTS respectively, they fail to show any change in their status when data sent (from PC) or received from another Xbee..

Has any one tried this type of connection ? and can offer advise with tat regard.

Stray solder balls? Sure I can clean them up with my soldering iron, but for this price we should get some sort of quality control.

Has anyone had any luck using this with an arduino? I'm trying to drive a dmx light using the tinker.it DmxSimple library.

How do I know what uart baud rate to use when connecting to the tranceiver.

The rs485 side is connected to a "black box"

HI,

I know this might be stupid, but is there an easy way to connect this to a usb to rs232 converter on the UART side?

Thanks

I considered using this breakout for my projects but the lack of full duplex capabilities had me looking elsewhere. I settled on the max488. A breakout of that chip would be very awesome. Of course the downside is that the max 488 is limited to 250 Kbps but I only needed it for serial translation from ucontroller to ucontroller.

to monitor the 485 bus while transmitting (for collision detection), would it work to separate pin 2,3 on the sp3485 and then ground pin 2? That would still leave transmitter control on the RTS, but would it then receive while it was sending?

There should be an assembled picture of this. In my haste to order I didn't realize the break-out was either RJ-45 -OR- 3.5mm screw terminal. The verbiage states "and" not "or".
Upon receiving it, I realized that the side-pins are the standard .1" header pins mentioned, not for the screw terminal which only mounts if you do not mount the RJ-45 connector.
It's my fault for not doing enough looking at the schematic/eagle board layout/PCB picture, but a simple picture of the completed PCB would have helped.

Hello everyone, i wish you could help me...
I bought this module a while ago and i was trying to make a simple application using a capacitive keyboard that sends data using RS485 protocol and my new Arduino Mega.
The thing that is going on is that i am able to send messages to my keyboard from my arduino, but not in the other way... the arduino code get stucked in the line where the serial is supposed to receiva data.
It is possible that the receiver module of the SP3485 chip is not working properly? or what else could it be?
Greetings,

I could use this in my next DMX-512 design.
Any chance for a full duplex transceiver? Possible even a breakout with optical isolation, protection circuitry, and a DC to DC converter for isolated power?