SparkFun Forums

[kiritb]

Hi,

I want to try and build my own PDA device for fun. I'm having a little trouble selecting an SOC to get started though.

Here are some of the onchip features I'm looking for :
- 100Mhz (preferably higher clock and bus speeds).
- USB 2.0 client (perhaps even a USB controller ?)
- LCD controller (upto VGA, higher resolution ofcourse would be nicer, or an alternative for an easy to implement LCD controller off chip)
- External memory access (RAM, External bootable Flash (CF/SD etc)
- SCI/SPI/I2C and a bunch of GPIO pins.
- key board controller (or an easy way to implement off chip)
- Vendor : I've worked with 8/16 bit freescale parts, but I'm open to any widely available platforms.(hope to use GNU tools so not tied to any dev environments)

General features:
- PCB - something that I can fit into a 4 layer board using eagle. Also I'll be making a one off piece so nothing too fancy in terms of <5mil traces etc.
- Assembly : I can solder QFN's on a toaster oven, havn't tried BGA's yet, wouldn't mind but would prefer QFN's or larger.
- Battery : Not too worried about that right now, hope to have a simple switching regulator on board for both wall transformers or any old batteries.
- Over all costs : Lets just say I'm not terribly averse to getting samples of some of the major IC's. (but its not too much of a big deal to have to buy it either) - Naturally lower is better.
- LCD : This ofcourse might be the killer in terms of cost, but any opinions on OLED's or other touch screen LCD's etc are most welcome.


Software :
- I definately want to run one of the open embedded RT linuxes on this device, and hopefully be able to use some of the UI's out there for embedded devices. So I'm not terribly averse to picking a hardware platform that already has linux ports and an active community around it.

Like I said this is aimed at being a learning experience, the key elements I want to take most out of the process are :
- designing a small packed board.
- greater familiarity with a 32 bit SOC and its features.
- embedded Linux development.
- Fun fun fun.

Any thoughts/ideas/comments, or links to projects on the net already doing something like this...

Thanks,
Kirit

P.S I will be posting this to a couple of other forums on the net so if you happen to see it on another forum please don't mind to much.

[nova]

These specs instantly made me think of three SoC's: the Xscale PXA, the Atmel AT91RM9200, and the Atmel AVR32 SoC. The PXA is a nasty BGA, as is the AVR32 (like 400+ pins!), but the Atmel AT91RM9200 can be either a PQFP 208 or a 256BGA, and you probably want the QFP. It doesn't have LCD, unfortunately, but the devel board from Atmel uses an Epson SGxxxx something controller that connects directly to the external memory bus (it is a really nice LCD/CRT controller). The addressing allows for up to 8GB of parallel external memory! it also has a USB client/host, 3+ USARTs, 3+ SSCs, SPI (with 16 chip selects if you use an external decoder), i2c, MMC, and a lot of other good stuff. In short, it is one amazing SoC! it also is widely supported by linux (part of main kernel tree) since like 2.2.x, so that shouldn't be a problem, and runs an ARM9TDMI core. my favorite part is the bootloader - it has 128K of ROM that boots the chip (selectable) and chooses between SPI DataFlash, i2c EEPROM, and parallel flash, or it can revert to ... USB! While I have never used this chip (I went with the Gumstix instead), I have looked into it a lot because it was my first choice before I found the Gumstix. I think that the AT91SAM9261 (?) is similar, but it *might* have LCD. The AVR32 from Atmel is a new core and the first chip they released based on it is AMAZING! it has everything! (I would probably buy a board if you made one that breaks out the right stuff - LCD + camera interface + all the stuff from RM9200 + hardware java) It even has an gcc toolchain. I don't know if linux has been ported yet, but it was in the process.
Hope that helps!