Request: Support Adafruit ServoHat

[Yaytay]

Hi,

I am using the Adafruit Servo Hat for controlling my servos, mainly because it lets me power them with a separate 6V supply. It would be really convenient for me if PiKrellCam supported the Servo Hat.

Would you be interested in adding support for it? Would you be interested in me hacking about with PiKrellCam to get it working with the ServoHat?

Jim

[billw2]

On Sat, 15 Oct 2016 23:48:37 -0700 Yaytay notifications@github.com wrote:

Hi,

I am using the Adafruit Servo Hat for controlling my servos, mainly because it lets me power them with a separate 6V supply. It would be really convenient for me if PiKrellCam supported the Servo Hat.

Would you be interested in adding support for it? Would you be interested in me hacking about with PiKrellCam to get it working with the ServoHat?

Jim

Sure, it would make PiKrellCam better to have Servo Hat support, so I would definitely be interested in your modifications if you would add that in.

Thanks, Bill

[Yaytay]

Hi Bill,

Well, I've got it so it'll talk to my servos (I can manually move the servos using the arrow buttons), but I can't work out how to get it to automatically track. What am I missing? The attached image shows what the screen looks like.

To talk to the Servo Hat I need to use i2c, and the least impact, most guaranteed to be installed, way to do that seems to be using wiringpi. So my change has added a dependency on libwiringPi, is that OK? The alternatives are:

• Linux smbus library (headers not installed on my pi, so likely not on others).
• pigpiod (should be a clean swap, that's what I use from Java, but only on recent raspbians).
• Bit bashing (too much like hard work).

I think you'll be able to see my work in progress on github: https://github.com/Yaytay/pikrellcam (bit new to git, normally use mercurial :))

Jim

On 16/10/2016 15:49, billw2 wrote:

On Sat, 15 Oct 2016 23:48:37 -0700 Yaytay notifications@github.com wrote:

Hi,

I am using the Adafruit Servo Hat for controlling my servos, mainly because it lets me power them with a separate 6V supply. It would be really convenient for me if PiKrellCam supported the Servo Hat.

Would you be interested in adding support for it? Would you be interested in me hacking about with PiKrellCam to get it working with the ServoHat?

Jim

Sure, it would make PiKrellCam better to have Servo Hat support, so I would definitely be interested in your modifications if you would add that in.

Thanks, Bill

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[billw2]

I don't have an image attachment in the email I got and on the issues page I don't see it either... Can you try again or send directly to me: billw-at-gkrellm.net but replace the -at-.

I want to avoid adding those dependencies so would like to have a C interface to the Servo Hat if possible. A couple of years back I had an experimental board with the PCA9685 and I wrote a C interface to it that could be used as a start. I've since put that board out of service and am actually out of town for at least a week and so can't get to it to try to revive it. So, let me give you the C code I have and maybe you can take a look to see if you can modify it to use for Servo Hat in PiKrellCam. I'll attach a tar file, maybe it will get through, if not, can I send it to you via email?

The program I used to test the pca9685 library routines is part of a much bigger test program so I'm not including it. But it's pretty basic, make sure defines are right or change the defines to use some config values, call piopub_pca9685_setup(), and then the other pca functions. But piopub refers to the experimental board I mentioned and those references should be changed to something appropriate for pikrellcam. There may be other compile issues if moving the code to the pikrellcam source, I haven't tried any testing. Also, pi_model() needs to be looked at. The return value the pca9685 code expects I don't think is what pi_model() in pikrellcam currently returns. I didn't look closely at that yet.

Bill pca9685.tar.gz

[billw2]

Oh, just noticed in the setup() routine, I was originally linking to glib, so g_new0() needs to be changed. It can be a cmalloc(), but it really doesn't need to be dynamic. It could just be a static declaration for pikrellcam purposes.

[Yaytay]

Hi Bill,

That code looks simple enough - I gave up with using plain file handles when I wanted to read the MODE register, but you don't bother doing that :) I'll replace my code with that and give it a go today, hopefully.

However, I've realised that I'm going to run into a problem - I have four other PWM channels running off the ServoHat, and I'm going to run into locking issues. So what I actually want to do is run everything through pigpiod. Given that we don't want extra dependencies, I was considering adding a further option to send the calls to pwm_width_func to a UDP endpoint - essentially giving a high speed callback mechanism to anything that wants to read it (a named pipe would be another option, but UDP has the advantage of throwing stuff away and not blocking). I'll see if I can make this work, and if so it's up to you whether you want it or not - I'll keep it separate from the raw PCA9685 stuff.

Jim

On 19/10/2016 01:13, billw2 wrote:

Oh, just noticed in the setup() routine, I was originally linking to glib, so g_new0() needs to be changed. It can be a cmalloc(), but it really doesn't need to be dynamic. It could just be a static declaration for pikrellcam purposes.

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