Hi, I have an 8051 controller that communicates over RS485 to other 8051 controller. The communication is half-duplex at baud of 57600, and...

Hi, I have an 8051 controller that communicates over RS485 to other 8051 controller. The communication is half-duplex at baud of 57600, and it works great. So far so good. Lately, I'm trying to make the 8051 device talk with a PC, since it is 57600 and I have RS232 RS485 converter this should be simple. I'm encountering strange problems at the 8051 reception, I never received what I se...

There are many MCUs with embedded Ethernet (MAC). It seems most of the open-source examples are lwip-based. I have to design a board with one...

There are many MCUs with embedded Ethernet (MAC). It seems most of the open-source examples are lwip-based. I have to design a board with one RS485 port and one Ethernet port. It could be seen as a serial-to-Ethernet converter, where the protocol on RS485 is proprietary. On Ethernet side I will contact a server (cloud) with a protocol that must be defined. At the moment, I don't need...

Hi, I am working on increasing the speed of data transfer between two electronic modules(each running OSE operating system)using...

Hi, I am working on increasing the speed of data transfer between two electronic modules(each running OSE operating system)using PPP(supported by OSE)over RS485. However be the baudrate i configure the maximum speed i get is 8KiloBits per second. Even if the baud rate has been changed to 38400kbps or higher it does increase the transfer rate. Is there some reason why it doesnt?It will be grea...

Hi all, I have to implement a very simple multidrop RS485 application, carrying slow 2400bps or even 1200bps data from a PC to a...

Hi all, I have to implement a very simple multidrop RS485 application, carrying slow 2400bps or even 1200bps data from a PC to a half-dozen devices about 300 feet away. The data flow is unidirectional; the devices don't talk back. Low cost is a significant factor in this. I plan to stick an RS485 driver on an AVR, weld on the small additional logic I need, and put it in a box. Two quick...

Hi, I've got an application that requires a number of environmental controllers be connected on an RS485 2 wire half duplex multidrop bus. I...

Hi, I've got an application that requires a number of environmental controllers be connected on an RS485 2 wire half duplex multidrop bus. I was looking at the Lantronix UDS1100 device servers (or even the older UDS100 / UDS10 ) to let me use the customers LAN so as to save wiring costs. I know a couple of UDS1100's can be placed back to back and tunnelling used to create a transparent R...

I have a typical two-wires RS485 network with multiple nodes. Only one node (the master) can start a communication: it sends a packet/request...

I have a typical two-wires RS485 network with multiple nodes. Only one node (the master) can start a communication: it sends a packet/request and receives a packet/answer. Usually the slaves can't communicate without the help of the master. The slaves could be different, so running a different firmware on different CPUs. Of course, all the slaves understand a common protocol (synta...

Hi, I'm writing some logging software for an embedded alarm panel design that uses an RS485 bus and proprietary protocol. I've attached the...

Hi, I'm writing some logging software for an embedded alarm panel design that uses an RS485 bus and proprietary protocol. I've attached the obligatory RS485 -> RS232 converter and connected to a free serial port on my PC. All good so far! Now, the alarm panel deliberately causes a parity error on the header byte of all packets transmitted on the bus. This parity error is used by all

I have manu SN75176 (www.ti.com/lit/ds/symlink/sn75176a.pdf) that I'd like to use to create a 2-wires RS485 bus with 10 nodes. However this...

I have manu SN75176 (www.ti.com/lit/ds/symlink/sn75176a.pdf) that I'd like to use to create a 2-wires RS485 bus with 10 nodes. However this transceiver isn't true fail-safe, so the receiver, if enabled, has an undefined output (with wrong data received from the UART) if the inputs are open or shorted. This is a 2-wires bus, so only one node transmits at one time. After transmitting ...

Hello there! I am new to low level programing. I have a Moxa 5232 Device server. I have a rs485 device that I like to be able to access from a...

Hello there! I am new to low level programing. I have a Moxa 5232 Device server. I have a rs485 device that I like to be able to access from a Linux computer. It is a 2 wire 1/2 duplex rs485 enabled device. After installing the Moxa drivers I have a "/dev/ttyr00 & /devttyr01" devices/ports on my Linux server. In order for me to access this device, I wrote a C program. It basically ope...

I have an half-duplex RS485 bus with 10-20 different nodes. Some of them are 8-bit MCU based, one of them could be Linux embedded. It's...

I have an half-duplex RS485 bus with 10-20 different nodes. Some of them are 8-bit MCU based, one of them could be Linux embedded. It's half-duplex, so it's important for the transmitter node to disable the driver as soon as the last transmitted bit is shifted out. Many small low-cost MCU has interrupt on transmission complete, so the delay of disabling the driver is usually on the ord...

I am designing an RS485 network, and was reading a Circuit Cellar article by Ambekar that describes a protocol that uses 9 bit characters, where...

I am designing an RS485 network, and was reading a Circuit Cellar article by Ambekar that describes a protocol that uses 9 bit characters, where a non-zero 9th bit indicates that the character is a control character. The described network used Intel MCS51 UART that can apparently be set to generate an interrupt only bit 9 is non-zero. This way devices on the network are not interrupted...

I've been reading up on RS485 drivers like the LTC485, 75176B and others. They look too simple in pin count to supply the + and - voltages...

I've been reading up on RS485 drivers like the LTC485, 75176B and others. They look too simple in pin count to supply the + and - voltages needed for differential drives. Are there some chips that supply the +/- voltages that other chips simple scavange and use? Or do these chips I note actually supply the +/- voltages for the differential outputs? The chip specs don't say. I've a proje...

I have a "smart device" SD that is the master on a RS485 master/slaves half-duplex network. The user interact with a "dumb device" DD (slave)...

I have a "smart device" SD that is the master on a RS485 master/slaves half-duplex network. The user interact with a "dumb device" DD (slave) and he should have the illusion to interact directly with the SD. All the relevant (for the user) info (status and settings) about the SD must be spread among the DDs, through a suitable protocol on the RS485 network. Some variables are read-onl...

I think you already know this trick: connect DE/RE signals of RS485 half-duplex transceiver to TX *negated* signal from UART and connect TX...

I think you already know this trick: connect DE/RE signals of RS485 half-duplex transceiver to TX *negated* signal from UART and connect TX input of transceiver to GND. If the bus is not driven by anyone, A signal goes high and B signal goes low thanks to the pull-up/down resistors. The trick uses the fact that the undriven bus and transmitting 1 is the same thing: A is high and B is...

I have a multi-drop two-wires RS485 bus. One node is the master and all the others are slaves. The master is the only node that is authorized...

I have a multi-drop two-wires RS485 bus. One node is the master and all the others are slaves. The master is the only node that is authorized to initiate a transmission, addressing one slave. The addressed slave usually answers to the master. The bus is half-duplex, so every node disables the driver. Only THE node that transmits data on the bus enables the driver and disables it a...

I have a bus network (RS485 based) with one master and N slaves. Each slave has a different unique 32-bits serial number. I was thinking on a...

I have a bus network (RS485 based) with one master and N slaves. Each slave has a different unique 32-bits serial number. I was thinking on a method for the master to autodetect the serial numbers of the connected slaves. Of course, the brute force method isn't acceptable for the time to test ALL the serial numbers. A more intelligent approach could be to discover the serial number

I know multi-drop two-wires RS485 bus must be considered a "transmission line" (so terminations are important) when the baud rate is high and...

I know multi-drop two-wires RS485 bus must be considered a "transmission line" (so terminations are important) when the baud rate is high and the cables are long, but I'm not able to quantify the "high baud rate" and the "long cable". For example, if the baud rate is 9600bps, how long could be the cables? And what if the baud rate is 38400? With those two baudrate and cables up to 10...

Each node on the half-duplex RS485 bus should start transmitting only if all the other nodes are receiveing (their transmitters are all...

Each node on the half-duplex RS485 bus should start transmitting only if all the other nodes are receiveing (their transmitters are all disabled). Usually the bus is master-slave with the master sending a frame request to a single slave and the slave send back a frame answer. In this scenario, slave must be sure to start transmission of the answer after the master has disabled its transm...

Who's good? Target is Linux 2.6.x with plenty of RS485 UARTS and Intel 82527 CAN controllers. -- Les Cargill

Who's good? Target is Linux 2.6.x with plenty of RS485 UARTS and Intel 82527 CAN controllers. -- Les Cargill

I need to remote RS232/RS485 signal over ethernet infrastructured network, which kind of device do you suggest me?? thanks a lot Bel

I need to remote RS232/RS485 signal over ethernet infrastructured network, which kind of device do you suggest me?? thanks a lot Bel