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manipulating CHUCK firmware
Most configuration is in a file called /etc/parameters.conf, on-board the drone. Some settings can (only) be changed with start-up parameters to the program dragon-prog.
Some config is in the startup-script, given as startup parameters to the main program: "dragon-prog".
Note: backup first! Make sure you mount the 'disk' as writeable! Settings get overwritten on reset and upgrade!
There are three known temperature sensors, see: https://github.com/uavpal/disco-docs/issues/9
Run BLDC_Test_bench -h to get a list of options. This program is used in both Disco and Bebop, so some options are only useful on either model.
BLDC_Test_bench -M -1 or -2 plays sound #1 respectively #2 in a loop.
Command-line parameters: https://github.com/uavpal/disco-docs/blob/master/dragon-prog%20-h.txt
dragon-prog can only have one instance, because /tmp/.dragon-prog.lock is used as lock file.
When you kill dragon-prog, the cooling fan stops. The fan can be turned on again with the command:
echo 1 > /sys/devices/platform/user_gpio/FAN/value
"I did experiment a bit with limiting disco video streaming bandwidth to FFPro. For persistancy I modded /usr/bin/DragonStarter.sh script and applied -q option to dragon-prog execution line. Normally I would get 2.4Mbit streaming while disco is recording in 1080p. You can go down with 0.8 Mbit steps - ie limiting streaming bandwidth either to 1.6Mbit or 0.8Mbit. One thing to note with dragon-prog -q option - you have to set bandwidth limit a bit ABOVE desired result - otherwise streaming bandwidth starts flipping between lower values. Ie for achieving 0.8Mbit limit you should set dragon-prog -q 1000 - and for 1.6Mbit it should be 1800 (and not 1600). It needs a bit headroom - otherwise bandwidth flipping occurs." at -q 500, the lag is really noticeable
The CHUCK has six servo connectors numbered 1-6. Number 1 and 6 are used to control the left and right elevons and number 2-5 are protected by red rubber covers. These servo ports can be controlled by software.
The servo outputs are exposed to userspace as PWM class sysfs directories:
| Servo port | Sysfs directory |
|---|---|
| 1 | /sys/class/pwm/pwm_4 |
| 2 | /sys/class/pwm/pwm_5 |
| 3 | /sys/class/pwm/pwm_6 |
| 4 | /sys/class/pwm/pwm_1 |
| 5 | /sys/class/pwm/pwm_2 |
| 6 | /sys/class/pwm/pwm_3 |
After boot only pwm_3 and pwm_4 of these are visible in the sysfs tree, since they have been created by dragon-prog. To create another entry, you need to send its' pwm number to /sys/class/pwm/export. For example, to create an entry for servo port two (pwm number 5), run this command:
echo 5 > /sys/class/pwm/export
The pwm directories contain three interesting files:
| File | Description |
|---|---|
| period_ns | The PWM period, in nanoseconds |
| duty_ns | The PWM duty cycle, in nanoseconds |
| run | 0 to disable pwm output, 1 to enable |
Servos turn to a position defined by the length of the pulse you send it. A 1.5ms pulse means "go to center", a 1.0ms pulse means "rotate to 45 degrees left" and a 2.0ms pulse means "rotate to 45 degrees right". Although exactly how much they rotate are device specific. Servos vary, and there is no standardization.
To send a 1.5ms (1500000ns) pulse every 10ms (10000000ns), write these these values to the pwm files:
echo 10000000 > /sys/class/pwm/pwm_5/period_ns echo 1500000 > /sys/class/pwm/pwm_5/duty_ns echo 1 > /sys/class/pwm/pwm_5/run
If you've peeked into /sys/class/pwm, you've no doubt seen device 10, 11 and 12 there and asked yourself what they are and if they are anything fun to play with? Well, they're not so fun I'm afraid:
| PWM device | Description |
|---|---|
| pwm_10 | IMU heating control |
| pwm_11 | Gyro clock control |
| pwm_12 | Camera MCLK control |
| pwm_13 | Camera MCLK control |
This disco-docs repository is community-driven Wiki.
We happily grant access to anyone who is interested in contributing, just reach out to us on Slack.