My board is called PeX which stands for Pi eXpansion.
I'm considering a Kickstarter to launch it. More info here:
http://bit.ly/1kwvXez. Last year I ran this
http://bit.ly/1pQQ5IT on IGG it was a poor turn out. Only got 10% funded. So I'm trying to collect feedback before risking a Kickstarter face-plant and the expense of prototyping a board that no one wants.
PeX is mostly a respin of my IGG campaign board, but with a socket to attach a RasPi host, a socket to attach an Arduino Uno host, RasPi expansion sockets, and Xbee wireless modules. Each 'wing' of the board can host ONE of: an Arduino Uno Shield OR a RasPi Expansion card OR Xbee modules. Only one wing will be a little different in that it'll also be able to host a Beagle Board cape and/or host depending on what connector is fitted. The main reason for this isn't the array of Capes, but specifically the range of well priced LCD capes. RasPi and Arduino just don't have good embedded LCD options (I'm not holding my breath waiting for RasPi MIPI-DSI drivers and options). I'd leave the BB socket unpopulated and ship loose sockets you could solder on. This allows you to solder wires direct if your application prefers, or IDC cable, or whatever. But by fitting female the sockets to the top side of PeX it'll support a Cape. Fitting male pins to the bottom side would allows a host BB or BBB to attach from beneath, albeit a bit awkward. You could also use a dual male/female part (
http://www.gradconn.com/2-54mm/pdf/BB02-KT.pdf) to allow both BB host and cape at the same time.
Everything will be tied together with an FPGA (of course.) The FPGA can be invisible to the user; coming pre-programmed with standard loads depending on your choice of host/shields etc. This board will not force you to learn FPGA unless it's what you want. It'll be either an Altera Cyclone IV EP4CE10 (10KLE) or a Cyclone V 5CEA2 (25KLE). It'll have SRAM, possibly DDR3 and a companion MCU for bootloading, USB Slave, ADC, SD Card, etc... FPGA source code will be supplied in SCHEMATIC form, as well as Verilog. Templates will be supplied for Pi host, Arduino host, etc... and the host will tell the FPGA what expansion card is connected to each wing with an I2C write to the FPGA so it knows where to route the IO. Data would then be steered by driving a mux in the FPGA logic. There can be infinite latitude here if you edit the FPGA schematic of course. For example if you have a serial shield you can steer the UART to that wing, while supplying I2S to another wing, while using GPIO PWM to drive motors on the 3rd etc, all quickly configurable in schematic form on Altera Quartus II's IDE (which also has a built in Logic Analyser called SignalTap that no one knows about.) To RasPi software, a setup like this would look like you had three Pi expansions stacked on top of one another simultaneously, but there will be driver development done for RasPi/Arduino asap.
The thinking behind PeX is that Arduino has far away the BEST set of cheap accessories. 300+ shields and there are some really great ones. RasPi has sold a zillion boards, has far away the best community support and depth of projects/development. BBB is completely open source and has the coveted stronger, cheaper LCD support. Digi Xbee is a quick way to bolt on some wireless action, with a variety of radios. So it would be cool to see people use something from each system based completely on its merits, not it connector and host. PeX will be Open Source under FreeBSD, and Altium files will go up on GitHub just like they have for all my other projects (helix_4 FPGA Module and it's dev boards.)
So this means:
- You'd probably save money because you can shop around between systems to get what you need for less.
- You can use a couple of expansions/shields at a time which is important if you need to see them all at once for control, etc
- You probably won't have a big arse Rube Goldberg ball of wires as your project: the FPGA cleans all that up
- You can use Arduino and Pi together. Sooooo if you have existing Arduino projects/code but need to add a GUI or internet-working etc you can just strap it on by moving your Arduino setup to PeX and then plugging a Pi in on the same board.
- Ditto for Beagle Board
- Xbee wireless hookups x 3
- You'll get a 4.3" LCD on your project for $60
https://www.sparkfun.com/products/12085 vs $145
https://www.sparkfun.com/products/11742- You get to use the FPGA if you want/need, including free Nios2, SignalTap, schematic editor, blah blah blah
So I need your help! Answer this for me:
1. Should PeX bother with the BBB Cape socket?
Is it a waste of effort just for an LCD? Should I just put a 4.3" LCD down on this board and charge +$80? Cutting the cape might save 2 layers on the PCB, so $10 or so.
2. Should I use Cyclone IV? Or Cyclone V?
PeX with Cyclone IV will be about $140 (shipped). With Cyclone V it'll be closer to $160. It'll take an extra month to delivery as well (no design reuse) but the Cyclone V is 2x faster than Cyclone IV and more useful in every way. Do people need more FPGA power?
3. Is this a sh#t idea? Is $140 too much for a Pi accessory?
4. Does anyone want DDR3 DRAM? probably 256MB @ 333MHz, 16bit wide physical (32bit wide virtual.) Again, this kind of ties in with the BB LCD Cape... video is a memory pig and the FPGA would abstract the LCD provide a frame buffer interface to the RasPi and Arduino, SPI or something parallel perhaps...
5. Would a few PMOD sockets around the periphery be a good idea? I might find some extra IO for that.
I really think that you could get some very professional results developing with a system like this, and I am trying really hard to keep it cheap and cheerful so everyone can have a bite. Please post your thoughts no matter how vile. In fact last time I posted to EEVblog I got a good bi^ch slapping. Come on EEVblog. Slap me again - I fu@king love it.
Brent.
PS. No this is not timed to coincide with the Papillio Duo launch. It's just a coincidence.