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Arduino-ish development board
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liam.zbasic



Joined: 25 Mar 2008
Posts: 163
Location: Southern California (Blue)
Posted: 05 June 2011, 5:49 AM    Post subject: Reply with quote
Some observations... it seems the 8-bit module world is experiencing a 32-bit invasion. Checkout these latest devices: the Uno32 Arduino compatible module for $27 and the 32-bit Maple Mini for $25. That's 10 dollars less than other 32-bit modules and nearly half the price of the venerable mbed.org device. And that's cheaper than most 8-bit modules with at least 24-pins, and far more capable.

http://leaflabs.com/store/

http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,719,896&Prod=CHIPKIT-UNO32

dlh - the competition will be fierce.

For me, the economics don't make sense for an 8-bit modules any longer. On the other hand, I will watch closely for a 32-bit Zbasic device if ever.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 05 June 2011, 10:53 AM    Post subject: Reply with quote
liam.zbasic wrote:
dlh - the competition will be fierce.
It might be, if this were intended as a commercial product., but it's just something I need. If I have to do my own and have time I'll publish an app note on it and release the Gerbers in the same open source vein of the original Arduino.

At this point, it looks like the Arduino Duemilanove will be easy to adapt. If so, anyone who wishes can follow suit to have a commercial model Zarduinon ONO. I think it will only require replacing the crystal and 328P. See the Amazon link in my previous post.

As for 32-bit, I've been Asking PureBasic for an ARM version for a couple of years, now.

@Mike: Still no camera but a little editing of the Zarduino ONO picture from my earlier efforts should be sufficient to show you what the R2 looks like. See...
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 05 June 2011, 13:22 PM    Post subject: Reply with quote
There seem to be dozens of Arduino compatible offerings. I found one that used a straight serial (DB-9) link to the USART.

But here's another compatible that looks suitable. Plus, the schematic on their site is much more geezer-friendly.I can see using more than one Zarduinon ONO in a stack with one as the main processor and a second (or more) dedicated to specific tasks. This would create a modular system where users can mix/match the features that suit their needs.

Question is how to control which, of multiple ZX-328n processors, gets its firmware updated without having to disassemble the stack of boards or unplug MCUs? One possibility is just to add switches in the DTR lines. Jameco used to sell some really cheap plunger switches. I bought some thinking to use them in place of headers/jumpers (the switches are much cheaper) but could not find a way to hold them neatly upright for soldering - they ended up all higgly-piggly which really looked bad in a group with them leaning every which way.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 05 June 2011, 16:55 PM    Post subject: Reply with quote
dlh wrote:
But here's another compatible that looks suitable. Plus, the schematic on their site is much more geezer-friendly.

I spoke too soon. I have no idea what the circuitry in the upper left quadrant of the schematic does. I think it has to do with the automatic selection of power source but I'm not sure just how. Has anyone seen an explanation anywhere?
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dkinzer
Site Admin


Joined: 03 Sep 2005
Posts: 2593
Location: Portland, OR
Posted: 05 June 2011, 20:29 PM    Post subject: Reply with quote
[quote="dlh"]
dlh wrote:
I think it has to do with the automatic selection of power source but I'm not sure just how. Has anyone seen an explanation anywhere?
The MOSFET is a P-channel enhancement mode device. The comparator driving the gate keeps the MOSFET turned off if Vin is sufficiently high. Without Vin applied, the MOSFET turns on allowing the USB 5V supply to power the circuitry.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 05 June 2011, 20:41 PM    Post subject: Reply with quote
dkinzer wrote:
The MOSFET is a P-channel enhancement mode device. The comparator driving the gate keeps the MOSFET turned off if Vin is sufficiently high. Without Vin applied, the MOSFET turns on allowing the USB 5V supply to power the circuitry.

So how high is sufficiently high? Will 3.3 volts turn off the MOSFET?

I'd like USB to be the 5V supply as it can provide up to 500mA but the 3.3V from USB is limited to 50mA which is far too little for a ZX-328l plus a shield or two so I want an external 3.3V supply. I have a Duemilanove en route so I guess I can always test it but I hate when the magic smoke escapes.

BTW, thanks, Don - as always.
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dkinzer
Site Admin


Joined: 03 Sep 2005
Posts: 2593
Location: Portland, OR
Posted: 05 June 2011, 23:28 PM    Post subject: Reply with quote
dlh wrote:
So how high is sufficiently high? Will 3.3 volts turn off the MOSFET?
As far as I can tell, the 3V3 is only used as a reference against which the divided Vin is measured. When Vin rises above 6.6V, the first op amp (IC5A), acting as an open loop, high gain amplifier (essentially a comparator), should change state to approximately +5. The second op amp (IC5B) is configured as a non-inverting unity gain amplifier so its output will also go to about 5V, removing the gate-source voltage from the MOSFET thus turning it off.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 06 June 2011, 2:26 AM    Post subject: Reply with quote
I'll have to wait for the Duemilanove to be sure but it seems all official Arduinos are 5V only.I keep coming back to my original idea of designing my own clone.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 07 June 2011, 1:55 AM    Post subject: Reply with quote
dkinzer wrote:
As far as I can tell, the 3V3 is only used as a reference against which the divided Vin is measured.
If I remove the fuse in the USB 5V line, will this mean that the external power (Vin) takes over?

Then I can use Vin (5V or 3.3V) to power the ZX-328n & ZX-328l, right? That leaves most of the existing power circuitry intact so it can be restored, if desired.

Now, to find a socket for the crystals.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 11 June 2011, 18:10 PM    Post subject: Reply with quote
This $30 Arduino Diecimila Compatible (DIP-28 ,DIP-40) board looks like it might be a better choice than the Arduino Duemilanove I ordered. Of course, shipping from Thailand may add substantially to the cost.

http://www.thaieasyelec.net/index.php/Arduino/ATmega32-Dev-Board-Arduino-Diecimila-Compatible-DIP-28-DIP-40-/p_133.html

This one accepts 28 or 40 pin chips. Removing the USB power fuse and removing or bypassing the regulator allows use of external 5V or 3.3V power. It looks simple to replace the crystal with a socket and use the board with the ZX-28n, ZX-28l or ZX-40n or ZX-40s. There's a link to the schematic on the referenced page.

EDIT: Shipping to USA costs $30, doubling the cost.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 13 June 2011, 19:05 PM    Post subject: Reply with quote
After seeing the DIP-28, DIP-40 board, I've concluded that my original idea is best. I have a PCB layout for the ZX-328 version. See this ZIP which has high-res JPEGs of the PCB layout. I tried attaching the file but it didn't appear to stick - I got no error message but did not see it in the preview.

I tried a combined version but decided it was beyond my pay grade. I think it requires multiple layers, which my software will do but its operator will not do. I think multilayer adds too much cost and I'm trying to make this as bare bones as possible.

I will do a separate DIP-40 version, later. EDIT: It's later.

The 10 pin strip along the right edge will be in the DIP-40 version but I don't think it is needed for DIP-28 as all of the pins connect to the system bus around the periphery.

Also, I need a PN for a socket for the crystals, if anyone has one.
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dlh



Joined: 15 Dec 2006
Posts: 285
Location: ~Cincinnati
Posted: 14 June 2011, 17:56 PM    Post subject: Reply with quote
I think the DIP-40 layout is finished. I added a 64KB SPI EEPROM.Does it make sense to also add the EEPROM to the DIP-28 version?

EDIT: The DIP-28 is also finished. I added the EEPROM to it, as well.Both versions are pin compatible with the Arduino. I will add the extra pins of the DIP-40 version to the shields I design - I have a few in mind.

I've tweaked both layouts so a single SMD stencil works for either. It will be 2-3 weeks before I order prototype boards - I have a couple of more complex boards to finish and want to combine all in a single order to save on shipping.

I've added one for the ZX-24 which will also handle BasicX and BasicStamp2.
SparkFun sells an ATmega328P with the Arduino bootloader pre-installed so the DIP-28 version can also grow up to become an Arduino. Rolling Eyes

All PICs have clamping diodes on all input pins so no level conversion is needed. Plus, you can use onboard comparators as inverters, making the serial interface very inexpensive - just a couple of current limiting resistors.
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