Tag Archives: rs-485


Here is a quick update on the RasPiComm+ status. We are currently working hard on the Raspberry Pi drivers and hope to get the RasPiComm+ out there in Q3.

RasPiComm Plus

RasPiComm Plus mounted on Raspberry Pi with GSM and 16 isolated I/O extensions

The board itself is a 56x74mm 4-layer board, most components are mounted on the bottom. The top-side only features 4 edge-board connectors for the modules, power LEDs and two JTAG debugging/programming headers for the Cortex M3/M4F and the Altera MAX V CLPD.

We currently have 6 RasPiComm+ modules which we are testing:


CAN bus, RS-485, 8 inputs and 8 outputs RasPiComm+ extension boards

  • 8 Input (with adjustable reference voltage, can be jumpered to 5V or 24V or fed from outside)
  • 8 Outputs (5V or 24V or fed from outside)
  • GSM module
  • RS-485 (two RS-485 on one board)
  • CAN (two CAN bus ports on one board, you’ll need the ARM Cortex-M4 option to use both simultaneously)
  • 16 isolated I/O (using th iC Haus iC-JX)

The firmware of the Cortex M3/M4F (both can be populated) will provide a bridge from the extension boards to the Raspberry Pi and interface with the drivers. The ARM microcontroller can be programmed from the Raspberry Pi for power users. It will come with a fully functional firmware and does not need to be changed though. If you want do do realtime or high relieability stuff you can do this by programming the ARM microcontroller.

The CPLD is also programmable via the Raspberry Pi, so changing configurations for different extension modules is easy.

RasPiComm+ bottom side

RasPiComm+ bottom side

The big metal box on the bottom side is an isolated DC/DC converter. This will be optional and powers both the RasPiComm+ and the Raspberry Pi from a 24V power supply. The battery holder is for the real-time clock backup battery for which we will also add driver support, so that the Raspberry Pi can get the current date and time.

The driver is very elegant I think. You can dynamically load and unload driver modules and they create an interface (for example /dev/ttyRPC0) to the specified module in case the module is a serial module (this applies to the GSM, RS-485 and the CAN module). This is already working quite well, we successfully sent SMS messages from the Raspberry Pi.

For the I/O modules we are looking into a driver interface similar to the Raspberry Pi GPIOs, but this is still work in progress, if you have suggestions what the best way is to implement I/Os leave a message 🙂

I will post separate articles about the RPCP extension boards to explain them in detail.

And if you have any other ideas how to make the RasPiComm+ even better let me know!


RasPiComm API

The RasPiComm API is here!

Martin did all the hard work and now it’s online: https://github.com/amescon/raspicomm

Check out the readme.md for instructions on how to install and use it. There is also a Demo-Tool where you can test the basic functions of the board.

We also added a deamon which you can use to forward RS485 communication via TCP/IP. We used it to make an Andoid App to control a stepper motor. Videos will follow soon!

RasPiComm Update

RasPiComm v3

I want to give you a short update about the status of the RasPiComm project.

We already have ordered parts for the first production batch of 1.000 RasPiComms. We expect all parts to arrive in 4 weeks, so the RasPiComm will be available in approximately 6 weeks.

We are also had a conversation with RS-Components. We are very confident that they will add the RasPiComm to their product lineup! So if everything works out the RasPiComm will be available worldwide!

Raspberry Pi with RasPiComm

Raspberry Pi with RasPiComm

The RasPiComm will most probably get a distinctive subsite on Designspark.

I made some changes to the final board, most of them are minor layout changes.

The pull-ups for the I2C were removed since they are already present on the Raspberry Pi. I still have to check how the I2C pull-ups are with the RasPi rev2.

ESD Protection
I also made an important change to the RS-232 and RS-485 ports. I added TVS-diodes for protection which is a massive improvement in terms of stability.

Here are the specs of the ESD-protection:

RS-232 port:

  • 300 watts peak pulse power (tp = 8/20µs)
  • ‹40 watts peak pulse power (tp = 10/1000µs)
  • ‹Transient protection for data and power lines to
    • IEC 61000-4-2 (ESD) ±15kV (air), ±8kV (contact)
    • IEC 61000-4-4 (EFT) 40A (5/50ns)
    • IEC 61000-4-5 (Lightning) 12A (1.2/50µs)

RS-485 port:

  • 400 watts peak pulse power (tp = 8/20µs)
  • ‹Transient protection for asymmetrical data lines to
    • IEC 61000-4-2 (ESD) ±15kV (air), ±8kV (contact)
    • IEC 61000-4-4 (EFT) 40A (5/50ns)
    • IEC 61000-4-5 (Lightning) 12A (8/20µs)
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