Okay, I admit it, we’re building something quite big this time. And robotic. So big, that it needs some embedded brains of the ARM scale (SmartQ7) and a microcontroller, that does all the dirty work (e.g. controls motors, gathers data from sensors and feeds that stuff to an ARM for processing.) However, disconnecting the micro for flashing, or running around with an ISP programmer is not an option.this thing moves pretty much.
So I decided to get SmartQ7 to actually flash this stuff. Since we’re running an atmega2560 on the main bot (really, we needed all those PWMs, INTs and GPIOs, not the code space, but a college insisted on putting everything to the max). So I borrowed from him some arduino board based on m1280 that’s quite compatible (actually – only flash size differs and I still think we could have pulled the same stuff with atmega640). Since I’m not using arduino IDE or libraries, the only thing that was left from arduino – the bootloader. It works with avrdude, and that’s enough.
The SmartQ7 is currently running a buildroot-based linux distro, with several new packages hacked into it. One of them is avrdude, the thing that we just can’t live without.
Getting it to cross-compile is pretty straight-forward, since it’s based on autotools that are quite well supported by buildroot.
You can get my buildroot package of avrdude via this link
It is already bundled with a patchset from ubuntu, that adds some features, including autoresetting of boards, that have DTR wired to the reset circuit. This will make your work even more comfortable.
Note, that the binary will be called arm-linux-avrdude
Now, it’s time to compile everything. I won’t go into detail, just point out some things that worth remembering.
We’ll need openssh, avrdude, wpa_supplicant (remember to check that in menuconfig). It’s also a good idea to include udev. then just type make.
Once you’ve transfered the whole filesystem on the SD card, you’ll need several files to edit. One of them is /etc/init.d/rcS
We can put some of out stuff right below, and we’ll need to bring up wifi here. Hope you’ve checked udhcpc, right?
On SmartQ wifi is enabled via :
echo 1 > /sys/devices/platform/smartq_gpio/wifi_en
Once we’ve anabled that, we turn on wpa_supplicant. We need this config:
Fill your values and you’re good.
The resulting script looks somewhat like that:
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echo 1 > /sys/devices/platform/smartq_gpio/wifi_en sleep 1 echo "Activating wireless" wpa_supplicant -B -c/etc/wpa_supplicant.conf -ieth0 -Dwext sleep 5 udhcpc eth0 echo "System active"
Then we’ll need to edit /etc/sshd_config to allow passwordless auth via a public key. Just edit that to be /etc/authorized_keys and then put your publickey there.
That’s it, if everything is correct, the tablet will boot and come online via wireless. You’ll see the ip obtained on the screen.
Now you can just ssh there. That’s quite cool, now we can move on to setting up a Makefile. Arduino-fans are out of luck, since I prefer pure C and hate arduino. Let’s do it via Makefiles, like real people do. In my case the flash target looks somewhat like that:
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flash: $(PROJECT).hex ifeq ($(REMOTE),"YES") @echo "Remote flashing in progress" scp $(PROJECT).hex $(REMOTE_USER)@$(REMOTE_HOST):/tmp/$(PROJECT).hex ssh -l $(REMOTE_USER) $(REMOTE_HOST) $(AVRDUDE) -c $(PROG) -p $(MCU) -P $(PORT) -b $(BAUD) -u -U flash:w:/tmp/$(PROJECT).hex else sudo $(AVRDUDE) -c $(PROG) -p $(MCU) -P $(PORT) -b $(BAUD) -u -U flash:w:$(PROJECT).hex endif
Note the variables that are worth setting up. I do it ib different profile files, that are part of my Makefile-fu =). Setting up REMOTE to “YES” enables the “remote” downloading of firmware: the resulting hex file is first transfered via ssh to the /tmp of my SmartQ7 and then flashed to the board. /tmp is worth being mounted as tmpfs, btw.
Oh, and do not forget to turn on usb host power. Just in case you’re host-powered. You want to control SmartQ from your PC via wifi – there’s an
app Makefile for that!
You can just place the following magic in smq.mk and -include into you own Makefile
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#This is a helper Makefile that allows to control different functions of SmartQ 7 via a makefile iface smq-log: ssh -l $(REMOTE_USER) $(REMOTE_HOST) "echo '$(TEXT)' > /dev/tty0" sw-gpio: ssh -l $(REMOTE_USER) $(REMOTE_HOST) "echo $(STATE) > /sys/devices/platform/smartq_gpio/$(GFILE)" sw-lcd: ssh -l $(REMOTE_USER) $(REMOTE_HOST) "echo $(STATE) > /sys/devices/platform/s3c-lcd/$(GFILE)" hostpwr-on: STATE=1 GFILE=usbhostpwr_en $(MAKE) sw-gpio hostpwr-off: STATE=0 GFILE=usbhostpwr_en $(MAKE) sw-gpio otgpwr-on: STATE=1 GFILE=usbpwr_en $(MAKE) sw-gpio otgpwr-off: STATE=0 GFILE=usbpwr_en $(MAKE) sw-gpio led1-on: STATE=1 GFILE=led1_en $(MAKE) sw-gpio led1-off: STATE=0 GFILE=led1_en $(MAKE) sw-gpio led2-on: STATE=1 GFILE=led2_en $(MAKE) sw-gpio led2-off: STATE=0 GFILE=led2_en $(MAKE) sw-gpio lcd-on: STATE=1 GFILE=backlight_power $(MAKE) sw-lcd STATE=1 GFILE=lcd_power $(MAKE) sw-lcd STATE=100 GFILE=backlight_level $(MAKE) sw-lcd lcd-off: STATE=0 GFILE=backlight_level $(MAKE) sw-lcd STATE=0 GFILE=lcd_power $(MAKE) sw-lcd STATE=0 GFILE=backlight_power $(MAKE) sw-lcd backlight-%: STATE=$* GFILE=backlight_level $(MAKE) sw-lcd ssh: -ssh -l $(REMOTE_USER) $(REMOTE_HOST)
And hey, it works!