G'day all,
I'm trying to build a data logger comprising of a SD card, a processor and an adc. The aim is to log the adc to the SD card.

I am looking for a nice neat softcore processor, that can be implemented on the xilinx fpga's. I currently have a spartan 3an starter kit, however, I would like the final FPGA chosen to be not a BGA (so i can manually solder it!). This will limit the number of available gates.

I am using elm chans fatfs which is written in ansi C, i have tested it on an atmega 128 and it works nice. The fact it is written in C, means hopefully i Can find a nice, free softcore that has a good C compiler to use. I would like to port this fat file system library to the softcore that i eventually choose (not use an avr).

I would like recommendations on a good soft core, with tool-chain. hopefully it uses no external peripherals such as the ddr (I don't want this on my final board!)

I have had a look at the T80, which looks promising... but not well documented.

I have also looked at the plasma, unfortunately I couldn't get it to run on my spartan 3an, and it uses ddr? some one needs to write some good tutorials on it:) or port examples to the spartan 3an starter kit (being the 3e is outdated). ISE didn't like the memory type Xilinx_16x either..

I have used picoblaze, unfortunately it doesn't have a C compiler and couldn't hold enough code anyway...

I suggest you have a look at the Microblaze. It fits easily in a XC3S500E and are available in VQ100 packages.

Although the mb license costs a little you have the upside of getting all the tools you need to do the design. It's also extensively tested by many companies so it's fairly bug free.

The bottom side is it is a 32 bit risc processor consuming huge amounts of code if you are writing your code in C. You might need an external program memory though.

If you already have the spartan 3e starter board just get a demo license for the edk and try it out.

Hi priscared

You may have difficulty finding an 8-bit softcore with a C tool chain. You may find it easier to look at compilers and see what targets are supported. One option is the Small Device C Compiler (SDCC). Chapter 4 of its manual lists the supported architectures.

HTH

Jeremy

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Hi Priscared,

From the description of your target application, it seems to me that the openMSP430 could be a good choice.
It is a clone of TI's MSP430 (16-bit) microcontroller and has a nice open-source compiler (mspgcc).
The openMSP430 also contains a serial debug interface which can be used with GDB to debug your code.

The core doesn't require any external peripheral (so no DDR) and there is already a implementation example for a small Spartan 3 FPGA (XC3S200).

Olivier

PS: note that if you're not happy with GCC performances you could also buy a proprietary one.

I have tried the AVR described in the cpu_lecture (http://opencores.org/project,cpu_lecture) with AVR studio and avr-gcc. Because my aim is only to prepare a project for students I have not checked extensively the C compiler but it works.
See the French document : http://perso.wanadoo.fr/moutou/ER2/CoreAtMega8.pdf

I have translated the French document of the previous answer :
http://perso.wanadoo.fr/moutou/ER2/CoreAtMega8_en.pdf
Hope it can help even if my English is not very good.