Embedded Systems Programming

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Embedded Systems Programming

• Networking on the puppeteer

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Networking in embedded systems

• Many, if not most, embedded systems require
  networking support
• This can be for development purposes
• From of Ethernet to download kernel to use NFS
  mounted root file system for development
• Or it can be for application/end user
• Web enabled devices, getting upgrades

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Networking fundamentals

• To network we require
• A NIC
• Network interface chip
• Software support for the chip
• A (working) device driver
• Protocol support
• TCP/IP, ftp, telnet, nfs
• A configured protocol stack
• Knowing how to talk
• A configured server/client
• Someone to talk to
• A network media
• A bit of wire!

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The Puppeteer - networking

• To network we require
• A NIC
• Network interface chip
• Software support for the chip
• A (working) device driver
• Protocol support
• TCP/IP, ftp, telnet, nfs
• A configured protocol stack
• Knowing how to talk
• A configured server/client
• Someone to talk to
• A network media
• A bit of wire!

• We have got
• SMCs91C96I
• FPGA complications
• SMC9194 driver in linux 2.4 kernel source
• Doesnt work!
• TCP/IP is in kernel
• Works
• Needs configuration
• Fairly straightforward
• We can use kenny
• LDAP problems
• Use Ethernet fly leads
• Remember to reconnect!

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The SMC91C96I Chip

• Standard series of chips
• Originally ISA bus chips
• Local bus, PCMCIA versions
• Horrendously complex
• The documentation leaves a lot to be desired
• Well supported under Linux
• Various versions of drivers around
• We will look at this later

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The SMC91C96I features

• Half and full duplex chip
• Has 6k bytes of on board ram memory
• Internal MMU
• Supports IEEE 802.3 (Ethernet)
• Status leds
• Has magic packet!

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Linux SMC9194 device driver

• Doesnt work out of the box!
• There are a few lines that need editing before it
  will compile
• It requires quite a bit of configuration for our
  system
• The memory address of the chip needs specifying
• The FPGA code needs writing and incorporating

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The SMC registers
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The SMC registers

• The SMC chip is located at ox20000300
• We repogram the MMU to reflect it at 0xF3800300,
  IO space
• This is done in pangolin.c

static struct map_desc pangolin_io_desc
__initdata / virtual physical length
domain r w c b / 0xe8000000,
0x00000000, 0x00800000, DOMAIN_IO, 0, 1, 0, 0 ,
/ Flash bank 0 / 0xf2400000, 0x10400000,
0x00030000, DOMAIN_IO, 0, 1, 0, 0 , / FPGA 0
/ 0xf3800300, 0x20000300, 0x00004000,
DOMAIN_IO, 0, 1, 0, 0 , / SMC91c96 ethernet
chip / LAST_DESC
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Probing the chip

• We need to probe the chip
• There are some bugs in the probe code that need
  fixing
• It finds the chip but cant set up the irq for it

unsigned int addr int base_addr dev-gtbase_addr
0xf3800300 dev-gtirq0 base_addr
dev-gtbase_addr SET_MODULE_OWNER(dev) / try
a specific location / addr ioremap(0xf3800300,
10 16) if (!addr) return
-ENOMEM retsmc_probe(dev, base_addr) iounmap(
addr)
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IRQs on the Puppeteer

• The interrupt structure on the StrongArm (and ARM
  generally) is very simple
• To create more complex interrupt structures in
  hardware designers will use interrupt controllers
• The Puppeteer use the FPGA for this task
• This means that we are dependant on the level of
  documentation of the Verilog/VHDL rather than the
  datasheets

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