RE: Verifying FEM Activation on BT840X (nRF52840 + SKY66112-11)

Arthur J Sary — Mon, 20 Jan 2025 17:15:49 GMT

Hello everyone,

I apologize for the silly question! It turns out the issue was simply missing the CPS and CHL pin configuration in the code. Once these pins were properly configured, everything started working as expected.

#include <zephyr/drivers/gpio.h>

int main(void)
{
	// Enable pins of SKY66112-11
	const struct device* gpio0_dev = device_get_binding("gpio@50000000"); // gpio 0

	//	Table 6. SKY66112-11 Mode Control Logic1
	//	Mode	Description 		CPS	CHL
	//	1 	Receive LNA 		0 	X
	//	2 	Transmit high-power 	0 	1
	//	3 	Transmit low-power 	0 	0

	gpio_pin_configure(gpio0_dev, 6, GPIO_OUTPUT); // gpio 0.06 - CPS
	gpio_pin_set(gpio0_dev, 6, 0);
	gpio_pin_configure(gpio0_dev, 8, GPIO_OUTPUT); // gpio 0.08 - CHL
	gpio_pin_set(gpio0_dev, 8, 1);
	
	// etc
	
}

However, one question remains: why doesn't it work when I set tx-gain-db=22? If anyone has any insight into this, I'd greatly appreciate your help.

Thank you!