Ganglion hardware specifications

yj

Hello,

is it possible to know more about this new board?

The processor, the A/D converter. (which chips).

The way SD card, AD, RFmodule are interconnected ?
 SPI bus may be?
If yes do they share the same bus?...

I am curious of to know more about it that what I see on this image :

   thanks,
  Yannick.

wjcroft

Yannick, hi.

There was a reply to a similar question in the comments section of the Kickstarter, you may have seen that.

https://www.kickstarter.com/projects/openbci/openbci-biosensing-for-everybody/comments

It's mentioned that a FAQ addressing some of these questions will appear on the Kickstarter.

Creator Joel Murphy & Conor Russomanno about 13 hours ago

Patrick, much of the planned hardware (A/D, processor, etc.) is still not finalized. We will detail what we know in the FAQ that we add soon. Regarding a smaller form factor for the Ganglion, we thought about it, but ultimately decided to keep the same form factor. Primary reasons: 
- we intend to create shields that need to be compatible with both the 32bit board and Ganglion. 
- we still have a lot of additional components that we need to squeeze onto the board (SD, accelerometer, radio module, etc.) 
- we want to break out all of the GPIO pins of the Simblee, maximizing hardware hackability. There are 29 GPIO pins on the Simblee and we want to expose as many of them as possible.

JakeStew

> much of the planned hardware (A/D, processor, etc.) is still not finalized.

I would suggest avoid the past weak points of the current hardware then.  Don't fool around with proprietary bluetooth solutions, use wifi.

Now would also be a good time to make a clean break and migrate to a STM32 platform.

> we still have a lot of additional components that we need to squeeze onto the board

I'd suggest not adding a bunch of stuff that most people won't use.  It's really easy, and really cheap to add a 6-10 DOF IMU board later.

I know it's tempting to pollute the design with extra stuff that is not biosignal related, but think how easy it would be to have a little I2C addon module with everything extra you could want, including the kitchen sink.

yj

Hello,

@wjcroft,

Thank's again William,  again I missed  the link to the comments, for my defense recognize that this link is rather discreet...

I am impatient to know the details which will appear in the FAQ.

 Yannick.

biomurph

@yj

The basic idea is pretty straight forward. We are using an ADC with wide bit depth, coupled with high impedance InAmps on the front end. We are not ready to release the BOM and the particulars, because we may likely be changing some aspects of it, and we also do not want to get scooped. When we start shipping the Kickstarter rewards, we will release all of the production files, schematic, and BOM.

Really appreciate all of the input! We will take it all under consideration.

Steve

I am using a Simblee chip on my project and have not been able to connect an SD card. The example read/write code provided in the Arduino IDE 1.6.5 does not even compile. If you have worked out this issue, posting the code would be greatly appreciated.

biomurph

@Steve, we will post the code as soon as we have it

That said, when we have working code blocks (like driving the SD card) we will post those parts as they are developed.

Joel

Steve

Joel,

          That would be great. 
Really appreciate it. The RF Digital folks make some great products, but
documentation on the Simblee is really lacking at this point.

Any idea on the time frame for the SD code? Is it something you are working on or is it way down on the list?

Thanks,

Steve

biomurph

We will likely hit the SD Card code for Simblee in Q1 of next year.

Steve

OK thanks again

Steve

Have you started the SD card code for Simblee yet?

lukmar

[original thread title: Ganglion sample resolution vs 32bit board]

I am hesitating between purchasing 8bit Ganglion or 32bit BoardKit for use simple biofeedback.

I know there are just 3 major differences between them: 

1. 4 vs 8 EEG channels

2. 8bit vs 32bit digital signal resolution

3. self-designed EEG amplifier chip vs professional ADS1299 from Texas Instruments

I think 4 channels are fine for my needs, but not sure if 8bit digital signal range has a significant quality impact on the EEG readings, graphs or plots. 

Can you tell me if there is a big quality gain between ADS1299 processor in 32 board compared to Ganglion?

Can anymore point me to the example plots / recordings of those 2 boards to compare the readings?

wjcroft

@lukmar, hi. I merged your question into this existing thread on Ganglion specs.

I don't believe the sample resolution has been stated on the Kickstarter, see the above quotes / links. It cannot be 8 bit samples, that would be too low to be practical for EEG. The TI ADS1299 A/D chip on the original boards has 24 bit resolution. 

In the post above, Joel @biomurph states, "We are using an ADC with wide bit depth, coupled with high impedance Instrumentation Amps on the front end." So that would imply 24 or at least 16 bit samples.

The Instrumentation Amplifer chips are not "self-designed", but are commonly used in A/D applications.

https://www.google.com/search?q=instrumentation+amplifier

The ADS1299 uses a delta-sigma design,

https://www.google.com/search?q=delta+sigma+adc

biomurph

The Ganglion will have 4 channels of 24bit data sampled at 256Hz.

We are using the MCP3912 ADC for digitizing the signal, and an Instrumentation Amp in front of that to provide the high impedance and low noise.

More details to be delivered when we are in production, which will be happening in September

petewall

Will we be able to use a few of the GPIO pins on the Simblee?  I would like to be able to add components for external triggers and digital outputs.

wjcroft

Some of the Simblee GPIO pins are shown on the Ganglion photo in the September update,

https://www.kickstarter.com/projects/openbci/openbci-biosensing-for-everybody/posts/1662837

The Shop page says that up to 20 of the GPIO's are exposed on pads, 

http://shop.openbci.com/collections/frontpage/products/pre-order-ganglion-board

petewall

@wjcroft Thanks!  I don't know how I missed that.

ogtoady

@biomurph What instrumentation amp is getting used?