Hi all,

As I seem to be getting a fair bit of interest in the p.Brain, I just though I would tell you my plans for this controller. I am currently working on a release version with a few improvements to my current test version, this should be finished early next year. The specs for the p.Brain are as follows:

> dSPIC33FJ128GP206 processor. (128Kb Flash, 8Kb Ram)

> On board 8Mhz Xtal or internal clock. (PLL will up to 160Mhz)

> 32Kb EEPROM

> 24 PWM channels up to 80hz (1 > 2ms pulse width)

> On board 3.3V reg

> 8 pins configured as analogue/digital IO

> 4 pins configured as digital IO or SPI port

> 2 Uarts

Uart 1: Inverted TTL

Uart 2: Either (Inverted TTL) or (RS232 ) or digital IO

> I2C or digital IO

> The p.Brain board has two 0.1" pitch 24 pin headers for convenient integration into a motherboard.

The p.Brain is approx 43x32mm and is designed to plug into a motherboard. The motherboard can be user designed to suit your needs, although I will offer my own design that I have used on my hexapods, which distributes the PWM channels, and provides convenient connectors to the p.Brains peripherals.

I plan on selling the p.Brain with no firmware, with the idea that is is used as a platform for robot projects. I will supply examples for Hitech C such as PWM output, Serial Coms, and EEPROM routines etc.

I may release a hexapod engine version that will have pre-compiled code that is configured using terminal software, however, I will not be releasing the hexapod engine code.

As an example of what the processor is capable of, my hexapod engine will run on the p.Brain with a 60Mhz clock at 80 frames per second!

I'm generally quite pleased with the way the p.Brain has turned out, and welcome your comments. My only concern with the design is the fact that microchip state that the dsPIC33 series of processors have a minimum of 100 erase/write cycles, 1000 typical. I have exceeded 100 in the past, but it seems a little low. I'm hoping that newer revisions of the chip will have better flash performance. Their latest 32bit processors have a minimum of 1000 erase/write cycles which is much better, also this 32 bit processor is pin compatible with the 33F series and offers a future upgrade path.

Matt.

someday i will buy one :)

Hi Matt

Spec looks quite detailed

As to the UART, TTL always seems to be best as it is quite easy to attach additional units i.e. bluetooth, Wifi or even USB SP. One trick I have seen on an RS232 port is to fit a standard 9 way but to insert breakout links in the TTL side to allow disconnection of the RS232 and redirect the TTL to another interface.

As to the re-writes of the memory/processor chips, will the chips be socketed or SMT. A socketed chip isnt too expensive to replace once it becomes life-expired. I know this can be an issue as while I was learning the Atmel 128 I must have programmed it 10 times a day for several months until it died. They were SMT so I had to replace the whole board.

Still it looks good and I look forward to getting to grips with whatever you come up with. The sample code you propose is ideal as it leaves the user to develop the movement code rather than re-inventing servo code.

One other before I go, will it able to cater for servos of varying voltages as the ones I have are 10.8V?

paulp (lynxmotion)

Hi Paul,

The RS232 transceiver on the second UART can software disabled, but you could also add the DB9 Mod you suggested to your own custom motherboard.

Currently the p.Brain has an SMT device in order to save space. I don't think I will be able to add a socketed version, however, I hope the p.Brain will be relatively inexpensive. It may even be possible to offer a replacement service? will have to see.

As long as your servos will accept a 3.3VPWM signal, then the motor voltage is irrelevent, so they should work fine.

Matt.

It all sounds good. I honestly think that what you are considering could fill a niche that is screaming out. There are controllers and bot-boards but as a pair, each is restricted by the limitations of the other and by the communications link that has to be in place. A controller with space on board for controller code would reduce the limitations. There are others but most only offer 8 servos which is too little.

Keep up the good work..

Yup I have been looking to develop code on a pic based controller for a while now and by the sounds of it, the p.Brain is perfect for anyone who wants a powerfull microcontroller that can deal with more than just ultra simple programs. Im pretty sure i'll be able to get some cash off the parents for one of these given its "educational" benefits.... :)

Hi Matt

Any further developments?

Hi,

I am just finalizing the hardware design for the p.Brain-ds24, if anybody would like to see the peliminary data sheet, please email me and I will send a copy. Feedback welcomed.

Matt.

Hi Matt, my name is Omar i´m from mexico, i have a question, are you going to have the p-brain for sale??

well, i ask that because i´m planning to construct an hexapod for my university and try to apply that control to many other things not only the hexapod, and i like to know if you have the controller for sale, or aprroximately for when you are going to have it for sale, or if you could help us to construct a similar p-brain..

thank you

Hi Omar,

I'm currently finalizing the p.Brain-ds24 hardware design. I can add you to teh pBrain distribution list and send you a hardware datasheet if you require. Email me or use the contact form.

Cheers, M@