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I need a device to read multiple Analog Inputs, and write 2 analog outputs

SensoredHacker0

Hello All, 
My Parent Company has been using Opto22 Groov Rios for expanding Analog IO to PLC systems. 
The issue we have with these devices is that the IO periodically freezes, maintaining the analog outputs. 
We make compression based hot water heaters, and this behaviour causes some undesired effects. 

The red box is indicating that the Analog sensors have stopped updating. 
image

Anyway, we are searching for a suitable replacement. The devices operate in a control panel, 
an may be subject to electrical noise, and heat from -10F to 120F
we would really like something with at least 10 Analog inputs. 

Modbus is fine. We have some experience writing other protocols, but that is frequently tedious in

A PLC programing environment.  We need a professional device, with a Din mounted case, no bare circuit boards.
Analog outputs 0-10V output would be great.

The groov Rios do what we want, the specs match our needs. Its their failure conditions that we have a problem with. We have brought this up with
Opto22, and no solution has been presented. Its a thing that happens. No one knows why, or has a fix. its been about a 
year of dealing with this, and I'm so over it. 

If there are alternatives, I would love to hear about them.

  • in reply to michaelkellett

    exactly. I mean the rios look fine. its this one weird bug effecting standard operations. I think at the time we went with them was in the chip shortage, and couldn't get anything else. maybe that was a clue!
    Anyway, lots of things look good on paper. Talking with folks lets you know what is legit. 

  • in reply to Jan Cumps

    I just remembered that BeagleBone people used the MSPM0 in I2C peripheral mode too (they call it I2C target mode for some reason). They used it to make the MSPM0 replace an I2C EEPROM and I2C ADC, they copied the register detail from real EEPROM/ADC chips. I'm hoping this code can provide a start: mspm0-adc-eeprom/source/modules at main · beagleboard/mspm0-adc-eeprom

    Actually, just thinking, if there's enough Flash space then the entire project could be used as-is, and append the extra code. That way a single device could be a multi-purpose EEPROM, ADC and UART bridge (I wouldn't be using the EEROM/ADC though).

  • in reply to shabaz

    Someone wrote a bitbang implementation for Pico PIO: https://github.com/thomasfla/pico-pio-uart-dma-rs485

    I didn't read the code yet. I'm gathering resources.

  • in reply to Jan Cumps

    I've been considering that part (SC16IS740), I might go with it,. I suspect the SD16IS740 is also possibly a pre-programmed microcontroller. I thought DIY with an MSPM0 might be straightforward because the behavior of the SD16IS740 part is well-documented because it is in turn based on a historical part which had a parallel bus.

    If I went the DIY route, then maybe to save time coding, I initially wouldn't bother with all the registers, I'd hard-code it to perhaps 9600 baud, and hard-code the RTS behavior all ready for attaching the RS-485 transceiver. I'd also not need a crystal oscillator, since the MSPM0 part doesn't use that. What was attractive is that I could use the MSPM0 parts for something else if it turns out less RS-485 interfaces are needed. Disadvantage is that it's another device to develop for and program! I'd only consider it if I can fairly quicky get it to work.

  • in reply to shabaz
    shabaz said:
    I've been considering creating the opposite end, a device to read in the measurements (guessing Modbus RTU?) and acting as an I2C slave.... So I'm curious to make a sort of RS485 to I2C bridge. Such parts do exist but are pricey.

    This NXP IC has RS485 to SPI / i2c parts: SC16IS7x0

    I have an AVNET Pi-based device here that uses the SC16IS740. It has 2 pins to change i2c address.

  • in reply to michaelkellett

    Hi Michael, it would be great to have per-port isolation, but a sort of compromise idea was to put one data acquisition module per RS485 interface and just accept that just one or a few ports would be used per module (each bridge interface having isolation, even if the module does or doesn't). It would be straightforward to add more RS485 interfaces to the "hub" processor if the bridge circuit had selectable I2C addressing. I don't mind too much if that is limited in practise to say 4-8 RS-485 interfaces, since another hub could be added (trying to keep this all low-cost but at the same time with some element of graceful degrading if one hub ever fails); it's for my brother's business (heating/air-con related; some of those RS-485 interfaces in future will go to other equipment, not data acquisition modules).

  • in reply to shabaz

    Would you go for isolation between the analogue ports or only between the block of analogue ports and the RS485 ?

    I think that your data recorder (I think you Road Tested one) is fully isolated , but that many industrial IO blocks only isolate in blocks (or not at all).

    MK

  • in reply to Jan Cumps

    I'd be interested : ) I've been considering creating the opposite end, a device to read in the measurements (guessing Modbus RTU?) and acting as an I2C slave.. for a couple of boring reasons, primarily I didn't have many free pins on my microcontroller. So I'm curious to make a sort of RS485 to I2C bridge. Such parts do exist but are pricey. Was thinking of using the good old MSPM0 chip since it's cheap and we know how to use it very effectively since we did all those experiments on it last year!

  • I may try to make something like this. 24 volt based, RS485 comms, The usual industrial voltage and current source / sinks. Decent isolation / protection and DIN housing.

    I have devices with RS485 and industrial IO that I could use to test it with.

  • Overdigit has analogue I/O with modbus, din mounted.

    4 chan analogue i/o configurable, 10 V:  EX04AIO

    4 channels can be I and O at the same time. They have pins for both, and both can be controlled via ModBus at the same time.