Looks like the default is 100 kHz. Seems like that should be fine, but you could also adjust config.txt to update that to 400 which is listed as the max
dtparam=i2c_arm=on,i2c_arm_baudrate=400000
I see the I2C commands in the data sheet? (but I had to expand “more pages” to get them). Maybe try setting the shutdown mode to “normal” and see if that succeeds?
Circuits.I2C.write(i2c, 168, <<0, 1>>)
I hadn’t seen the “more pages” button, thanks for pointing that out. I filled out a module based on what I saw in the arduino library and it looks like the arduino library writes a 0x01 value to the 0x00 register and calls that a “CMD_ENABLE_OUTPUT”… I hadn’t seen that in my first round of experimentation.
It also looks like the arduino library always sets the PWM channels and then does a final write to the “update” register which seems like a way to tell the chip to update all of its values at the same time?
I’m traveling this week so i can’t test anything until next Tuesday, but if anyone else wants to give it a try it will be interesting to see if my module actually produces any light
took a peek and this python code/lib might be helpful https://github.com/pimoroni/sn3218-python/blob/main/library/sn3218/__init__.py
especially the CMD_ENABLE_OUTPUT, enable_mask - and it also seems one has to issue a CMD_UPDATE after each cmd..
keep us posted;-)
I got the LED’s working. The address detection is not a standard so not always supported. Looks like that is the case here for the SN3218 in this setup. But I was able to write to the address and it was a matter of understanding the flow of how it expects to turn on.
You can dump this in IEx and get a little LED spin action with random colors:
{:ok, i2c} = Circuits.I2C.open("i2c-1")
# Docs say this should be 0xA8 (0b10101000), but the python uses
# this address and it works, so ¯\_(ツ)_/¯
addr = 0x54
# Enable LED control
Circuits.I2C.write(i2c, addr, <<0, 1>>)
# I don't know where the LED's are in this control register, so just turn
# them all on - #yolo
Circuits.I2C.write(i2c, addr, <<0x13, 255>>)
Circuits.I2C.write(i2c, addr, <<0x14, 255>>)
Circuits.I2C.write(i2c, addr, <<0x15, 255>>)
loop = fn l ->
# SN3218 supports 18 LEDs. The Trilobot seems to have 6 RGB leds with
# each color gamma tied to a single PWM LED register, effectively
# making the LED control triads of 3 register addresses
#
# | LED | Red register | Blue register | Green register |
# | ------------------ | ------------ | ------------- | -------------- |
# | LIGHT_FRONT_RIGHT | 1 | 2 | 3 |
# | LIGHT_FRONT_LEFT | 4 | 5 | 6 |
# | LIGHT_MIDDLE_LEFT | 7 | 8 | 9 |
# | LIGHT_REAR_LEFT | 10 | 11 | 12 |
# | LIGHT_REAR_RIGHT | 13 | 14 | 15 |
# | LIGHT_MIDDLE_RIGHT | 16 | 17 | 18 |
for led <- 1..6 do
# SN3218 has auto incrementing register addresses. This just means
# we calculate the first register (red) and then write 3 bytes which
# will write 1 byte to the 3 registers, starting with the initial (red)
reg = led * 3
rgb = for _ <- 1..3, do: Enum.random(0..255)
# Adjust the PWM for each RGB of LED N
Circuits.I2C.write(i2c, addr, [reg | rgb])
# Apply all the settings
Circuits.I2C.write(i2c, addr, <<0x16, 1>>)
# Little sleep gives a rotating effect on trilobot
:timer.sleep(100)
end
l.(l)
end
# Don't block our IEx
led_spin = spawn fn -> loop.(loop) end
Thanks for posing Jon! That’s super encouraging. And thanks for the comments in your code, really helpful to know how the 18 channels get mapped into the 6 LEDs.
I’ll be back home on Tuesday and I can’t wait to play around a bit with the Trilobot
Thanks again @jjcarstens I tested out your code and broke it into a couple of modules in my Trilobot repo
It feels a little too-small to make it it’s own hex package, but hopefully these modules are pretty re-usable if anyone wants to drop them into another Nerves Project
I wanted to create an easy way to hook up the button inputs to any custom functionality that people might want for their Trilobots. So I made use of the property_table library which is already part of Nerves and added a commit to makes it easy to write a process that subscribes to button change events.
https://github.com/mmmries/trilobot/commit/7b7be2229e4e22e1f90a5c8153c14488e991b4ec
And wired up the x button to a little pre-defined drive pattern. Now my kids are getting interested
Maybe this is way too ambitious, but I would love to be able to do something like this racing project as well
