Sometimes it seems that hardware engineers go out of their way to may the job of software engineers difficult. Here are my top 10 tips (plus two bonus slides) that will make integration to smoothly

1. 10 things that make software
integration easier
H/WExpo 2016
10 things that make software integration easier 1 Copyright © 2011-2016, 2net Ltd

2. About Chris Simmonds
• Consultant and trainer
• Author of Mastering Embedded Linux
Programming
• Working with embedded Linux since 1999
• Android since 2009
• Speaker at many conferences and
workshops
"Looking after the Inner Penguin" blog at http://2net.co.uk/
https://uk.linkedin.com/in/chrisdsimmonds/
https://google.com/+chrissimmonds
10 things that make software integration easier 2 Copyright © 2011-2016, 2net Ltd

3. The problem
• Q. How many hardware engineers does it take to
change a light bulb?
10 things that make software integration easier 3 Copyright © 2011-2016, 2net Ltd

4. The problem
• Q. How many hardware engineers does it take to
change a light bulb?
• A. None: we’ll fix it in software
10 things that make software integration easier 3 Copyright © 2011-2016, 2net Ltd

5. The problem
• Q. How many hardware engineers does it take to
change a light bulb?
• A. None: we’ll fix it in software
• Q. How many software engineers does it take to
change a light bulb?
10 things that make software integration easier 3 Copyright © 2011-2016, 2net Ltd

6. The problem
• Q. How many hardware engineers does it take to
change a light bulb?
• A. None: we’ll fix it in software
• Q. How many software engineers does it take to
change a light bulb?
• A. None: that’s a hardware problem
10 things that make software integration easier 3 Copyright © 2011-2016, 2net Ltd

7. Some ideas
• Here are my top 10 ideas that will make software
integration easier, faster and less stressful
• I work mostly with Linux and Android, so they are
biased in that direction...
10 things that make software integration easier 4 Copyright © 2011-2016, 2net Ltd

8. 1: Choose chips with good software
support
• Lack of support for $OS is biggest bugbear
• Don’t rely on what the salesman says: demand to
see the code
• Check that it:
• is up to date
• works with the version of $OS you are using
• will be supported over the lifetime of your product
10 things that make software integration easier 5 Copyright © 2011-2016, 2net Ltd

9. Background on vendor kernels
• In the case of Linux, ask if the support is in mainline
• If not, why not?
Mainline
Vendor
4.N 4.N+44.N+24.N+1 4.N+3
4.N 4.N+4
10 things that make software integration easier 6 Copyright © 2011-2016, 2net Ltd

10. 2: Stick to the vendor reference
design
• Keep it simple: minimal changes are good for us
10 things that make software integration easier 7 Copyright © 2011-2016, 2net Ltd

11. 3: Fit a JTAG connector
• How else to debug the bootloader?
10 things that make software integration easier 8 Copyright © 2011-2016, 2net Ltd

12. 4: Fit a serial console
• Once the $OS kernel has started, debug is usually
via a serial console
• It is really helpful to reserve a UART for this purpose
10 things that make software integration easier 9 Copyright © 2011-2016, 2net Ltd

13. 5: Fit more RAM
• Double it!
• You would be surprised how much memory we can
use up
• It takes developement time to reduce the memory
footprint
10 things that make software integration easier 10 Copyright © 2011-2016, 2net Ltd

14. 6: Fit more flash memory
• See 5
10 things that make software integration easier 11 Copyright © 2011-2016, 2net Ltd

15. 7: Think about in-field update
• Double amount of flash for redundant copies of OS
• Or, fit removeable storage (USB, uSD) for local
upgrade
10 things that make software integration easier 12 Copyright © 2011-2016, 2net Ltd

16. 8: Don’t use the main CPU to flash an
LED
• Use LED with flash mode: saves waking the main
CPU up every half cycle
• Likewise, maybe use a buzzer rather than employing
a full audio stack to sound an alert
10 things that make software integration easier 13 Copyright © 2011-2016, 2net Ltd

17. 9: Hard real-time in microcontroller
• In the case of Linux, it can perform hard real-time
mission-critical tasks
• But, bear in mind that the hardware of a typical SoC
is not deterministic
• Probably better to offload to a PIC or Cortex-M
10 things that make software integration easier 14 Copyright © 2011-2016, 2net Ltd

18. 10: Anti-brick mode
• Provide some way to recover when the bootloader is
broken
• e.g. image load via USB, serial, JTAG
10 things that make software integration easier 15 Copyright © 2011-2016, 2net Ltd

19. Bonus: Don’t multiplx those pins
• Try to avoid multiplexing ports (e.g. serial) so that one
port can perform several different roles
• It complicates drivers and applications
• There is always a case when you need both functions
at the same time
• Example: serial console and GSM modem
multiplexed to the same port, making it difficult to
debug the modem
10 things that make software integration easier 16 Copyright © 2011-2016, 2net Ltd

20. Bonus: Board ident
• Fit some means of identifying one version of a board
from another (e.g. GPIO pins with pull up/down
resistors)
• Means that one s/w image can be used on multiple
boards
• (make sure there are enough bits to cover the
anticipated number of variants)
10 things that make software integration easier 17 Copyright © 2011-2016, 2net Ltd

21. Utopia
Stopping Bootlog daemon: bo
Poky (Yocto Project Refer
sama5d4-xplained login: root
root@sama5d4-xplained:~#
root@sama5d4-xplained:~#
root@sama5d4-xplained:~#
• Hardware and software engineers should talk to each
other more
• It helps if software engineer are involved in the early
design
10 things that make software integration easier 18 Copyright © 2011-2016, 2net Ltd