Suggestion: Super-simple & small board for BOE that creates analog pins
John Kauffman
Posts: 653
Analog to Digital board specifically for BOE?
I work with people like artists and ecologists that want to use a uCon platform simply as a tool to sense and react, learning as little electronics as possible. Their situation is like me using this browser simply to read and write on this forum, learning as little as possible about TCP/IP.
I teach using BOE but students are attracted to the Arduino because it is so easy to attach a resistive sensor to an analog input which automatically puts the sensor’s output in a variable. I know a Prop has analog in, but switching everything from BOE to Prop platform is a big proposition at this point.
Does it make sense for Parallax (or someone else) to bring to market a small board to add analog input to the BOE’s pins 0-3 so that there are the equivalent to the analog pins of an Arduino? It might be something like this http://www.robotshop.com/content/PDF/datasheet-i2c-adc.pdf.
But
1) physical layout to sit right on top of the BOE pins header,
2) on bottom output pins to go to BS 0-3, on top input sockets to go to resistive sensors
3) 8 bit resolution might be fine, Maybe an option to go to a WORD size variable
4) hopefully down in price to $5-10. On price, a Homework board + this analog converter would come to $60 which would be competitive with Arduino at $35 (given other advantages of BOE).
By pushing this board down on top of pin headers 0-3 the BOE could take a 0-5v input and have it appear as 0-256 in a variable. I am guessing it would be a single chip with 4 op amps or a 4-channel ADC chip. I wish I had the skills to make something at a commercial grade of quality.
On the software side it would be a line or two of code that does not require the user to understand serial comm or I2C or RCTIME. Just copy/paste the line(s) & change the pin number. Power up the BOE and the sensor value will be sitting in a variable.
This little item would go a long way to solve what I am seeing is the biggest advantage of Arduino over BOE. I use the BOE because of some advantages over Arduino, but I keep getting flak about the ease of using Arduino analog pins.
I work with people like artists and ecologists that want to use a uCon platform simply as a tool to sense and react, learning as little electronics as possible. Their situation is like me using this browser simply to read and write on this forum, learning as little as possible about TCP/IP.
I teach using BOE but students are attracted to the Arduino because it is so easy to attach a resistive sensor to an analog input which automatically puts the sensor’s output in a variable. I know a Prop has analog in, but switching everything from BOE to Prop platform is a big proposition at this point.
Does it make sense for Parallax (or someone else) to bring to market a small board to add analog input to the BOE’s pins 0-3 so that there are the equivalent to the analog pins of an Arduino? It might be something like this http://www.robotshop.com/content/PDF/datasheet-i2c-adc.pdf.
But
1) physical layout to sit right on top of the BOE pins header,
2) on bottom output pins to go to BS 0-3, on top input sockets to go to resistive sensors
3) 8 bit resolution might be fine, Maybe an option to go to a WORD size variable
4) hopefully down in price to $5-10. On price, a Homework board + this analog converter would come to $60 which would be competitive with Arduino at $35 (given other advantages of BOE).
By pushing this board down on top of pin headers 0-3 the BOE could take a 0-5v input and have it appear as 0-256 in a variable. I am guessing it would be a single chip with 4 op amps or a 4-channel ADC chip. I wish I had the skills to make something at a commercial grade of quality.
On the software side it would be a line or two of code that does not require the user to understand serial comm or I2C or RCTIME. Just copy/paste the line(s) & change the pin number. Power up the BOE and the sensor value will be sitting in a variable.
This little item would go a long way to solve what I am seeing is the biggest advantage of Arduino over BOE. I use the BOE because of some advantages over Arduino, but I keep getting flak about the ease of using Arduino analog pins.
Comments
It doesn't really make sense for Parallax to do this. For one, you can already trivially measure resistance sensors using RCTIME. There's plenty of documentation and the only part needed is a small stable capacitor and maybe a resistor depending on the range of the sensor's resistance. You can also measure voltages this way (see this webpage).
Parallax is rapidly moving to the Propeller Activity Board ($50) which already has analog inputs and outputs among other things. The Propeller ASC+ ($50) also is compatible with many Arduino shields and there's a thread here recently where someone has been translating some of the Arduino libraries for use with Parallax's GCC compiler and has gotten some Arduino programs to run on the Propeller.
Someone else may be willing to make up a small breakout board for the Stamp BOE and an ADC0831 or MCP3202 or MCP3204 (for 4 inputs). The software requires four lines of code (see the demo programs for the devices).
A breakout board for the HomeWork Board would be tough. It wouldn't be enough to connect to P0-3. You'd also need Vdd and Vss. You can already mount an ADC0831 or MCP3202 on the breadboard area and connect it to the Stamp with a few jumpers as shown in a number of examples.
You are right, by putting it at the p0-p3 end of the dual row header on the BOE you also have access to the Vdd and Vss pins there, and there is a nice empty space to the side where the rider board wouldn't interfere with anything mechanically.
The $5 target is tight for anything unless it will be made in quantity. Dedicated ADC chips tend to be on the expensive side, a couple of bucks right there. If I were undertaking that project, I might consider using a pre-programmed 8-pin PIC chip and take advantage of its 4 10 bit ADC channels. Then it would take only one Stamp pin and a SEROUT command to select a channel, and the same Stamp pin to receive back the analog value. PIC chips are much cheaper than dedicated ADCs.
That said, I reiterate that it is drop dead simple to put a 2-channel ADC0802 in an 8-pin DIP package right on the BOE breadboard, put on jumper wires to 3 stamp pins and power, and plug in the subroutine, and there you have it. A 2 channel 8 bit ADC. If instead the ADC is off on its own little rider board, you student is going to have to put a jumper from the rider board over to the main breadboard, and then wire the sensor into a little voltage divider circuit. They still have to get their hands dirty and not cross the signals! Same as Arduino.
Thanks for thoughtful responses, a hallmark of your participation on these fora. I particularly appreciate the two different perspectives. I'll send to Andy and he can figure what is best for P'lax. I would try it myself through G'Gansta but have never laid out a board or written code at a level I would consider professional. Sounds like a great project for a student that wants to make her own internship.
At a higher level, I'm sort of at a crossroads. I feel increasing pressure to move from BS to a newer platform (analog pins is one reason, off the shelf Arduino libraries and brand recognition are others). I would prefer to stay with BS mainly because PBASIC language is easier & I have so much invested in BS2 (h'ware, s'ware examples, lessons). Do I switch everything to Prop or to Arduino? I would prefer to stay with Parallax because it is such a great company with whom the students can continue buying. I guess my Autumn task will be assessing what I have in BS that can be ported / reused, and get flying with Prop for the new year.
I don't mean to sound like some of my retired students that lament the passing of COBOL. Getting switched to focus on Prop will be exciting and finally get me past the little tinkering I've been doing. I'll check education forum for others in same transition with classes.
Again, thanks.
http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/328/Default.aspx?txtSearch=whats+a+microcontroller
I'll check in with Andy to see that he receives the idea and that the Education team discusses it.
Regarding a switch, I suggest you go straight to Propeller for the following reasons:
- Use of a modern, multicore processor
- C programming language.
- Support from Learn.parallax.com
- Upcoming Propeller Activity Bot (next month!)
- Parallax support
There are many more reasons for an educational customer to use the Propeller, but these are the key ones. We're working very well with a significant and capable team to develop the best educational program in existence. And knowing how you use these products I'm sure you'll be happy once you get started with Propeller C.Drop me your shipping address and I'll send you a couple of Propeller Activity Boards. I don't know where you are right now, but last time we talked in Washington D.C. you were living somewhere in SE Asia.
All the best -
Ken Gracey
An aside, about art... My wife and I took a tour of the di Rosa art museum near Napa couple of weeks ago, and there on the wall among all the other eclectic art was hanging a box with a BASIC Stamp I on its original carrier board showing through the grill. The piece also included a motion sensor, a speech synthesizer (speakjet?) and a speaker, so as the observer approached it would emit a pithy comment such as "I'll never leave you", or "I wish you were dead". Artist Bruce Cannon. A lot of technology art (as opposed to art technology) is consciously retro.
A tour of our manufacturing facility would make you happy right now - the BASIC Stamp quantities haven't fallen off - still steady. However, where they are used has shifted. What we used to sell in individual quantities are now sold in robots and educational kits.
I've been to the di Rosa art museum on Highway 12 but I poached the place from my bicycle so I didn't get to go inside the reception center. Instead, we rode around the grounds to see all of the more static artwork (that pile of file cabinets was impressive!).
They should stack and arrange them like Stonehenge.
PE - Or try this with 0805 and 0605 caps! ("Microhenge", for Hack-a-day)
-Phil
http://www.flickr.com/photos/0honeybear0/528679717/in/set-72157600305721753
I didn't get very close to it because we took the inside tour. Ken, were you able to ride your bike onto the grounds without going thru their security? They seemed touchy about people wandering around without one of their docents.
They have several hoopdie cars there, decorated with art objects, old electrical gear, panel meters, telephones, relays etc. You could do that with the tombstoned SMT parts, old integrated circuits, even make it light up and shimmer.
The educational kits do live on then, for use in schools, in parallel or at a different level than the Propeller curriculum?
Well, that's not a "pile of file cabinets" at all.
Well, I best fess up! We I rode our bicycles onto the grounds with the idea of having lunch somewhere and then taking a quick look at some of the exterior art displays. Once I got through the turkey sandwich a very polite docent introduced himself to us and eventually directed us back to the reception area to buy a ticket and tour. Liability is their big concern, with all the hills, artwork, and opportunities to trip and crash. We didn't have time to do the tour at that point, so we told him we'd come back another time. Getting our bicycles across the busy Hwy 12 took at least ten minutes due to traffic.