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  • Case ID: 295981
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BLE doesn't work in the custom board of NRF52840

salvatore_

Hi, 

I recently started using Nordic microcontrollers and I have designed a custom board based on nRF52840 and its works except for Bluetooth.

First of all, I'm using vscode+zephyr to program the board, and the firmware I'm using is a sample firmware "peripheral_uart".

  1. First I tried to upload the firmware on nrf52840DK and it works properly! - I see the device via the nRF connect smartphone app 
  2. Next, I upload  the firmware onto the custom board and...
    1. The firmware is uploaded correctly.
    2. UART connection(TX[P0.14]-RX[P0.09]) OK!
    3. All other gpios are working
    4. Log print "Bluetooth initialized" - but if I try to search for the device with the nRF connect smartphone app, I can't find it

I have done several tests, both hardware(HF crystal is correctly mounted), and software. I've tried resoldering the board but nothing still doesn't work. I have been using these microcontrollers for a short time, so my little experience does not help me solve the problem.

Schematic:

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  • 0 in reply to salvatore_
    salvatore_ said:
    1. The pi network is in the updated wiring diagram and I don't think that is the problem.

    Are you referring to C3, L1 and C7?

    These are the radio matching/filtering circuit, they can't be used to match the antenna impedance as well.

    salvatore_ said:
    2. 32MHz crystal part number: C648963 https://lcsc.com/product-detail/Crystals_HD-7D032000M01_C648963.html

    This crystal have a rated CL of 12pF. The correct value for C4 and C5 can be calculated using(assuming insignificant trace capacitance):
    C= 2*CL - 2*Cpin

    The typical pin capacitance(Cpin) for XC1 and XC2 is 3pF. Using this equation a better suited capacitance for C4 and C5 is 18pF.

  • 0 in reply to Bendik Heiskel

    I changed C4 and C5, but the problem is still there. I'm powering and programming the board with nrf52840DK, so I don't think that is the problem. I think the problem is caused by some configuration.

  • 0 in reply to Bendik Heiskel

    If it helps here are the configuration files of the board:

    .dts 

    // Copyright (c) 2022 Nordic Semiconductor ASA
// SPDX-License-Identifier: Apache-2.0

/dts-v1/;
#include <nordic/nrf52840_qiaa.dtsi>

/ {
	model = "custom_nRF52840";
	compatible = "custom,custom-nrf52840";

	chosen {
		zephyr,sram = &sram0;
		zephyr,flash = &flash0;
		zephyr,code-partition = &slot0_partition;
		zephyr,console = &uart0;
		zephyr,shell-uart = &uart0;

		zephyr,uart-mcumgr = &uart0;
		zephyr,bt-mon-uart = &uart0;
		zephyr,bt-c2h-uart = &uart0;
	};

	leds {
		compatible = "gpio-leds";
		led0: led_0 {
			gpios = <&gpio0 13 GPIO_ACTIVE_HIGH>;
			label = "Green LED 0";
		};
		led1: led_1 {
			gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
			label = "Green LED 1";
		};
		led2: led_2 {
			gpios = <&gpio0 15 GPIO_ACTIVE_HIGH>;
			label = "Green LED 2";
		};
		led3: led_3 {
			gpios = <&gpio0 16 GPIO_ACTIVE_HIGH>;
			label = "Green LED 3";
		};
	};

	aliases {
		led0 = &led0;
		led1 = &led1;
		led2 = &led2;
		led3 = &led3;
	};
};

&adc {
	status = "okay";
};

&gpiote {
	status = "okay";
};

&gpio0 {
	status = "okay";
};

&gpio1 {
	status = "okay";
};

&uart0 {
	compatible = "nordic,nrf-uarte";
	status = "okay";
	current-speed = <115200>;
	tx-pin = <14>; //14//6
	rx-pin = <9>; //8
	rts-pin = <0xFFFFFFFF>;
	cts-pin = <0xFFFFFFFF>;
};

&flash0 {
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x0 0xc000>;
		};
		slot0_partition: partition@c000 {
			label = "image-0";
			reg = <0xc000 0x72000>;
		};
		slot1_partition: partition@7e000 {
			label = "image-1";
			reg = <0x7e000 0x72000>;
		};
		scratch_partition: partition@f0000 {
			label = "image-scratch";
			reg = <0xf0000 0xa000>;
		};
		storage_partition: partition@fa000 {
			label = "storage";
			reg = <0xfa000 0x6000>;
		};
	};
};

    _defconfig

    # Copyright (c) 2022 Nordic Semiconductor ASA
# SPDX-License-Identifier: Apache-2.0

CONFIG_SOC_SERIES_NRF52X=y
CONFIG_SOC_NRF52840_QIAA=y
CONFIG_BOARD_CUSTOM_NRF52840=y

# Enable MPU
CONFIG_ARM_MPU=y

# Enable hardware stack protection
CONFIG_HW_STACK_PROTECTION=y

# Enable RTT
CONFIG_USE_SEGGER_RTT=y

# Enable gpio
CONFIG_GPIO=y

# Enable uart drive
CONFIG_SERIAL=y

# Enable console
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

# additional board options
CONFIG_GPIO_AS_PINRESET=y

# CONFIG_PINCTRL=y

  • 0 in reply to salvatore_

    Since the firmware works correctly on the nRF52840 DK the problem would be with the custom hardware. As I mentioned, if the antenna is not tuned correctly the very little power will be transmitted. If C3, L1 and C7 are the only components between the ANT pin and the antenna, I expect the antenna impedance will not be tune to 50 ohm as is required for good antenna performance.

  • 0 in reply to Bendik Heiskel

    I am not very convinced that the problem is the antenna, okay the signal might be very weak but not nonexistent. I also tried to run a test via RSSI Viewer but nothing, it is as if the antenna is not totally connected.

    Could there be some error in the circuit? I followed configuration no. 6.

    https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf52840%2Fref_circuitry.html

    I cannot find the problem, perhaps I should redesign the board using an antenna PCB as in the dk. However, before redesigning the board I would like to be sure that the problem is that.

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