Can I directly drive solid state relais with GPIO?

Technical Support
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1

Hello
I have a toradex Ixora Board with an Apalis TK1 processor Module.
In addition I have solid state relais that require 3V and 15mA current to turn on.
Is it possible to directly connect such a solid state relais to one of the GPIOs(1-8)?
if yes, do I need to do a special configuration on the pin for that?
Another question: Some GPIOs I like to use as input. How can I configure the pin to activate an internal pull-up resistor?
Regrads
Sektionschef

2

On Apalis TK1 for loads >10mA per pin or >25mA per port, I’d recommend using an external buffer or a transistor.

GPIO 1-7 can be configured as input via sysfs. For all pins the configuration (muxing, pull-up/down)
is located in the device tree, mainly in those files:
/arch/arm/boot/dts/tegra124-platforms/tegra124-apalis-v1.2-pinmux.dtsi
/arch/arm/boot/dts/tegra124-platforms/tegra124-apalis-v1.2-gpio.dtsi

3

For reliability you need to focus on the minimum values. You also need to be careful when using Apalis TK1 since some of the pins are not connected directly to the SoC, but go to the level shifters with 12mA maximum pin current.
In conclusion, It’s possible to source/sink up to ~30mA out of the gpios connected directly to the SoC, assuming they’re of the proper type and no other pins on the same port are heavily loaded.
Remember that different Apalis modules will have different gpio current sourcing capabilities, therefore we’re recommending an external buffer for inter-modules compatibility.

4

Thank you!
In TegraK1_Embedded_Design_Guide.pdf I found the following information in table 116:
Does it mean I can drive around 50mA at 3,3V?

Regards
Sektionschef