RoboSavvy Forum

Should I make the jump???

2006-09-05T08:02:31+01:00

Also, re a new processor board. What about the AVR Butterfly. Mega 169, LCD, tones of I/O, very cheap at around £20

Statistics: Posted by pepperm — Tue Sep 05, 2006 8:02 am

Should I make the jump???

2006-09-04T06:29:21+01:00

The serial comms circuitry is the same as that used on the AX-12 (if my tracing is accurate) which in turn is functionally the same as the one used on the CM-5. The CM-5 & AX-12s don't use a 7404 inverter but drive both enable lines directly from the processor. The 74126 is not an inverter it is a non inverting buffer. I'm not sure why they have done it this way, maybe because they use the other 2 buffer gates on the CM-5 to buffer and select the RS232 or Zigbee connections or so that the data is not inverted when it hits the processors.

The code in the example C code should explain the the use of the RS485 port and its enable lines, because although the code is for the CM-5 it would be very similar for the AX-12 and indeed AX-S1.

So to send data you need to set PD7 high. You could also set PD6 low but it wouldn't matter if it was high.

To receive data PD7 must be set low and PD6 high. Data comes in on Rxd and goes out on Txd. Exactly the same as on the AX-12 (unless my tracing went wrong again some where)

We could use an invertor in the select line but then we would probably need more chips on the board as we would still need a device that had enable inputs. We could use the inverting version of the 74126 but then the data would be inverted in the Mega8.

Do you think you can write code for this circuit?

Mark

Statistics: Posted by pepperm — Mon Sep 04, 2006 6:29 am

Should I make the jump???

2006-09-04T03:07:41+01:00

limor wrote:
please excuse a software guy's humble ignorance.

I dont understand the serial communication wireing. To send a bit to the coms line, the MCU has to put PD0 on 0 and/or PD6 on 1? and similarly when the imcoming signal is high (or low) what happens to PD7 and PD1?
(Correction: sending data involves PD0 and PD6 / receiving involves PD7 and PD1.. but my question remains)

I believe that he is using two I/O pins PD6 and PD7 combined to form the direction port as shown in the CM-5 internal circuit (HALF DUPLEX UART). Their diagram uses an 74HC04 inverter to make sure that only TXD or RXD is active, but not both. In Mark's circuit the controlling software would have to make sure that only one of these two pins is set high at any point.

I assume that you will want to use the builtin USART support that is in the ATMEGA8 chip. So your code may look something like: (Note this code is sortof based off of the C++ classes that are defined in the Seattle Robotics Society Workshop robot level 2 examples. These are up at:
http://www.seattlerobotics.org/WorkshopRobot/level2/index.php

Code:: OUT RXEnable ('D', 6); OUT TXEnable ('D', 7, false); COMM comm ('D', 0, 'D', 1); ... // To output a packet you might try something like RXEnable.Low(); TXEnable.High(); // For each byte in the packet you might call something like: comm.TxCh(ch); // waits for bit_is_clear(UCSRA, UDRE) // before setting UDR= ch ... // To receive information you might do something like: TxEnable.Low(): RxEnable.High(); // Set up a loop to read in a packet with all of the appropriate // error checking... while(!comm.IsCharWaiting()) ; // checks RXC bit in UCSRA ch = comm.InKey(); // gets byte from UDR register

Note in the example code above you could replace the polling for input character available or transmit complete with interrupts...

Please forgive me if I misunderstood the schematic as I am also a software guy!

Statistics: Posted by KurtE — Mon Sep 04, 2006 3:07 am

Should I make the jump???

2006-09-03T21:43:29+01:00

please excuse a software guy's humble ignorance.

I dont understand the serial communication wireing. To send a bit to the coms line, the MCU has to put PD0 on 0 and/or PD6 on 1? and similarly when the imcoming signal is high (or low) what happens to PD7 and PD1?
(Correction: sending data involves PD0 and PD6 / receiving involves PD7 and PD1.. but my question remains)

Statistics: Posted by limor — Sun Sep 03, 2006 9:43 pm

Should I make the jump???

2006-09-03T21:20:35+01:00

And this is the PCB.

I'll make one as soon as I am back from my trip.

So now we need some code...............

Mark

Statistics: Posted by pepperm — Sun Sep 03, 2006 9:20 pm

Should I make the jump???

2006-09-03T20:03:46+01:00

How about this as a starting point?

I'll work on a PCB for it, I'm using the mega8 PDIP version at the moment because that is all that I have in my draw. I have some free 74HC126's on the way from Texas Instruments, and a local Atmel distributor may send me some SMD samples. I have asked.

Once we have some working code we can work on a better board, perhaps with different IO. I think this will work as a good development board though.

Mark

Statistics: Posted by pepperm — Sun Sep 03, 2006 8:03 pm

Should I make the jump???

2006-09-03T18:34:30+01:00

Limor

From a programmers perspective, which of the Mega8's I/O would you like to bring out on a connector, if you had any 8 pins to choose from?

How about all Port C pins (6 pins) and PB1 and 2. PD0, 1, 6 and 7 are used for the serial comms and PD2 for an led (as on the AX12). PB3, 4, 5 and RESET are used for the programming port.

Mark

Statistics: Posted by pepperm — Sun Sep 03, 2006 6:34 pm

Should I make the jump???

2006-09-03T13:09:47+01:00

Nope, not familiar with those boards but the AX-12s use the mega8 so it should do the job, it does in the AX-12 and AX-S1s.

It has A/Ds and Uarts.

Mark

Statistics: Posted by pepperm — Sun Sep 03, 2006 1:09 pm

Should I make the jump???

2006-09-03T11:51:30+01:00

wow! that's hardcore moonshine PCB making..

are you familiar with these Olimax boards that DanAlbert mentioned in the other post?

Could one of these serve as our Bioloid sensor board?
We need is a processor that has some A/Ds and a decent internal clock that can do UART at 1mbps. probably 16mhz is needed.
what about powering the board with the high voltage that is found on the Bioloid bus?

Statistics: Posted by limor — Sun Sep 03, 2006 11:51 am

Should I make the jump???

2006-09-03T11:23:36+01:00

Yep, I make single sided PCBs at home, in my bath! You can have a look at some of my work for robot wars (a few years ago now) here:

http://www.askt47.dsl.pipex.com/Robot_WarsStag/electronics.htm

I realise there are PDIP versions of the Mega8 but I can also make SMD versions. I will see what I have in my components draw. I am currently trying to reverse engineer the AX-12+ PCB so that the board designed will be in some way compatible Mega8 port wise. I don't suppose you have any of the code that runs in the AX-12s do you?

Of course, we could just use AX-12+ servo boards, if there are spares available.

It may take me a week to come up with a first stab because unfortunately, I will be away from home this week.

Mark

Statistics: Posted by pepperm — Sun Sep 03, 2006 11:23 am

Should I make the jump???

2006-09-03T09:58:09+01:00

Great!
Do you make at home the single side board?
BTW: Atmega8 also comes in PDIP package which (doesnt need SMD work).

I've ordered the Robostix. will start a separate thread about it..

Statistics: Posted by limor — Sun Sep 03, 2006 9:58 am

Should I make the jump???

2006-09-03T08:29:22+01:00

limor wrote:
If you design the board I will write the code and i'm sure Inaki and others will help aswell once we get started. Do you know of companies that can not only make the PCB in quantities of 2-5, but also procure the parts and do the SMD soldering ?

I'll start comping up with something simple first then. Mega 8 based with some I/O taken to a connector, single sided PCB so I can make it at home, SMD. This way we can develop the comms code and begin to work out how to present parameters to the CM-5.

Mark

Statistics: Posted by pepperm — Sun Sep 03, 2006 8:29 am

Should I make the jump???

2006-09-02T15:14:47+01:00

I just noticed the Robostix product from Gumstix.
It is basically a stand-alone Atmega128 board with lots of pinouts.
Can't beat $50.

Statistics: Posted by limor — Sat Sep 02, 2006 3:14 pm

Should I make the jump???

2006-09-02T14:19:12+01:00

pepperm wrote:
I can design hardware but the problem for me is software.

If you design the board I will write the code and i'm sure Inaki and others will help aswell once we get started. Do you know of companies that can not only make the PCB in quantities of 2-5, but also procure the parts and do the SMD soldering ?

inaki wrote:
I think any replacing board should be also compatible with the existing board. It should support BCP at least.

We could have an Atmega128 on this sensor board instead of a smaller Atmel ($15 in digikey). We'll just have to write a boot-loader that mimics the one on the CM5 (in theory we could copy the protected boot-loader code from the CM5 to the new board's Atmega128 but it means somehow tapping into the chip's SPI legs..

Regarding The advantage of having the Gumstix processing power onboard the robot is that we'll be able to run dynamic closed-loop control algorithms and acheive movement like Qurio, Assimo and Aibo. Running and skateboarding can be acheived. And another important aspect is that running Linux will be welcome by many new programmers.

Statistics: Posted by limor — Sat Sep 02, 2006 2:19 pm

Should I make the jump???

2006-09-02T12:58:05+01:00

I think any replacing board should be also compatible with the existing board. It should support BCP at least.

I wanted the source code precisely because I want to know some details about the BCP interpreter in order to improve my tokenizer.

Pepperm, I can help you in the side software if you want.

I think I would start with a sensor module using the serial interface already used in the Bioloid kit.

Statistics: Posted by inaki — Sat Sep 02, 2006 12:58 pm