Wednesday, 3 July 2013

The new mini biggie

First build of my Mini-web board.
It has:
ATMEGA1284 (2 serial ports, 16K ram, lots of other goodies....)
DS1307 battery-backed clock
micro SD card
Ethernet (WIZ820 module)
Radio socket-strip (for nRF24L01 or other)
Breadboard friendly
Atmel 6-pin ICP header

Initial testing with Arduino software, programming by AVRISP MkII.
Ethernet, RTC, SD and radio all tested. 
Soon, I'll put an Arduino bootloader on and try serial programming. It should work with a FDTI basic, using DTR to reset. The resistor/cap are in place on the reset line and the DTR has a pin of the board-edge.
The required TX/RX/DTR/+V/GND are not all together as per the Arduino standard but a small wire harness will hook it up OK.
Serial programming was an afterthought, I use the ICP header for all my stuff.

Its a layered construction. The SD socket is under the Ethernet connector

The white connector is the RS485.
6-pin ICP is on the closest corner

Bottom of PCB, battery holder not yet present.

Top without the WIZ820 module.
SD socket is between the mounts for the Wiznet module.

From left to right, 1st 8-pin SM chip is the RS485 driver, next one is the DS1307 RTC

Socket strip on the right-edge is for a radio.
This can be a sparkfun nRF24L01 breakout, or a RFM12 breakout, or a RFM70/73 breakout.

And a Sparkfun radio board plugged in.

So, 2.4Ghz link, 128K flash, 16K ram, RTC, micro-SD slot, Wiz820 ethernet and RS485 on the 2nd serial port.

I suppose I'd better learn to program it now.....


  1. Testing all going well.
    Currently board is running a web-server (for home automation), a web-client (posts to Thingspeak), also logging the post-data to the SD card using time from the RTC, sending diagnostic info out of the 1st serial port and the RS485 port is hooked into my wireless sensor gateway.
    Radio functionality of the board itself has been tested and is good but at this point its not in use in my testing sketch.

    This board is running at 16Mhz. Parts on the way to make up another one to run at 22.11Mhz


  2. Tried an Arduino bootloader for the ATMEGA1284p and it works fine.
    This particular bootloader is from the soon-to-be-released Goldilocks board at...
    and then available from Freetronics..
    Phillip Stevens did the work to tweak the bootloader for the Goldilocks, I just loaded it and it all worked.
    I tried a 16Mhz version and a 22.11Mhz version.

  3. I think I have arrived at a 2nd build version now.
    It has more flexible power options. Positions for two regulators on board, a 5V and a 3.3V.
    With the two power rails on the board, the micro (and RS485 if fitted) can be run at 5V for full speed. The other items all run a 3.3V. The 5V rail can be connected to the 3.3V rail (with no 5V reg fitted) and the whole board run at 3.3V. Also now fitted,
    A power LED
    A LED on one of the I/O pins
    A reset button
    The radio connector is now the cheap nRF version as per ebay (and many other sources)
    Solder bridges to bypass the RS485 chip so the logic level serial goes to the I/O connector (you cant have the RS485 chip fitted in this case)

    The PCB is done, I just need to check it over for a few days and see if I spot anything wrong then I'll get a batch made.

    Its 5mm wider so still well within the 50x50mm PCB area at Seedstudio (and others)

    Since I'm ordering boards, I'll do a RFM12 adapter that fits onto the radio connector, I use both.

    If it all works OK then I think that will do for me. This will be the release version.


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