Converting 29USD ET AVR board to 60+ USD wiring compatible board

November 11, 2008 at 11:10 pm (Uncategorized)

We all love arduino, don’t we? And we love it because it’s cheap, flexible, has great user support, because it’s opensoruce (so we don’t feel bad about all the pirate software we stole J ) and so on. But arduino has it’s disadvantages as well, for me that is mostly a low pin count (yes, you zcan use port expanders, but that’s still not the same as having natively high pin count). Arduino’s older bigger brother ­wiring is using the same programming language, but is based on ATmega128 instead ATmega 168. That means that you get 53 pins instead of 11, and 128kb (instead of 16kb) of memory for your programs (check this site for details). The downside? It costs 60+ $ (ok, a worthy upgrade in US, but in EU this comes closer to 100€ with postage, and that is whole army or arduinos … ). So what I will show you is how to convert cheapest (to my knowing) atmega128 board http://futurlec.com/ATMEGA_Controller.shtml) to be wiring compatible.

Hardware:

Part list:

• · ET AVR controller board
• · 32khz crystal
• · 14 Contact IDC Socket Connector (http://futurlec.com/Connectors/IDCC14.shtml)
• · Switch (optional)
• · Led (optional)
• · Resistor (optional)

Tools:

• · Everything you need for some light soldering
• · Some sort of programmer (you can use the one that is sold at futurlec, otherwise just Google around a bit)

Most of the more expensive ATmega128 boards do not need any hardware modifications to run wiring, but this one is missing 32khz watch crystal, so we need to add it (unlike arduino, wiring will not operate without it, because it uses it as main clock, for time keeping etc..). When we are at it we will also add a bootloader switch and a status led for it. Note that these two components are not need, you can simply install time based bootloader to use instead of button based one and led is only for indication.

To avoid unnecessary hustle with creating pcb for those 3 simple components will simply put them around connector that plugs into ETCLCD port. Take a look at schematics below:

My version looks like this:

I assume you have already worked with this kind of connectors and that you have basic soldering skills, so I will not go into details on how to build it (if you are having problems you can mail me, or ask in the comments). Basically you just stick wires into connector, clamp it together, solder components and hot glue everything together (or put it into shrink tube, or use your imagination).

Second step: software (bootloader).

Before we can use the wiring we need to program our AT mega with appropriate bootloader. You can find source code for wiring bootloaders on this site: http://www.avride.com/article/wiring/ . Bellow are my two versions of bootloader.

First one is button based, that means that you have to hold bootloader button down while you reset the board to enter bootloader, also note that when you are in bootloader the led will turn on (PG0 will be high). Note that this is V1 bootloader.

BOOTLOADER DOWNLOAD

Second one is time based, that means that you do not need to press bootloader button, instead every time you reset the board it will enter the bootloader for 8sec and than the normal program will start. Downside is of course that you will have to wait 8 sec every time you turn on the board (very very annoying when you are programming or debugging it). Note that this is V1 bootloader.

Programming fuses:

If you are using PonyProg for programming, here is the screenshot of the appropriate fuses.

Otherwise here is copy/past from wiring bootloader site:

Fuse setting is same as Wiring Board

Extended: 0xFF
High: 0xCC
Low: 0x3F

Important bit fuse
Boot Flash size 1024 words : BOOTSZ=10
Boot Reset vector enable : BOOTRST=0
CKOPT=0
BOD at 4.0V, : BODLEVEL=0
BOD enable : BODEN=0
Ext. crystal/resonator High Freq.; Start-up time 16K CLK + 64ms. : CKSEL=1111 SUT=11
Watchdog disable: WDTON=0
OCD disable: OCDEN=0
JTAG disable: JTAGEN=0
SPIEN enable: SPIEN=0

A quick note on bootloaders, I was unable to use V2 bootloader source code, if any1 succeeds please contact me.

Everything should be ready now, connect your brand new wiring clone to computer via RS232 port (yeah I know, it’s not usb but it’ll do), start up wiring, select correct COM port, select firmware version V1 and try to upload some simple blinking sketch.

About ports and pin numbering:

The problem is that the layout on the ET ATmega board is completely different than the one on the wiring board, so how do you know which pin is which? Just check the bellow diagram and everything will be crystal clear (I hope). Now go and play with your new toy, make something great, publish it under some OpenSource license and feel good about yourself.

Diagram PDF

Notes on using other boards:

You can of course any other ATmega128 board, as long as it is working at 16mhz, and has 32khz watch crystal. For pin mapping just check schematics on the official wiring site.

Update:

If you are converting a ET-AVR stamp board, you should solder the crystal between PG3 and PG4, as illustrated. The led is of course optional and should be tied between PG0 and GND. You should use a time based bootloader, to avoid the need of a button. Because stamp board doesn’t  have RS232 converter u will have to use external(just google TTL UART to RS232 (or USB) ) and you have to connect it to PE0 (receive) and PE1 (transmit) pins.  Note that I don’t have any of these boards, so this is untested.