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  • Case ID: 342336
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Enabling UART on nRF9161 DK for application use?

nrao32

From what I can see in the documentation, UART0 is used by default for "non-secure" / application logs and UART1 is used for "secure" app logs. I am needing to interface with another MCU using UART, but I'm having a hard time figuring out how to enable my non-secure portion of the app access this peripheral.

To start with, I disabled UART0 for app logging, switching to J-Link RTT:

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CONFIG_SERIAL=y
CONFIG_UART_ASYNC_API=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_RTT_CONSOLE=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n
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With the above, I am able to use the J-Link RTT Viewer to view my app logs instead of the VCOM0 / UART for logs.

I then added the following to my device tree overlay:

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&pinctrl {
uart0_default: uart0_default {
group1 {
psels = <NRF_PSEL(UART_TX, 0, 27)>,
<NRF_PSEL(UART_RTS, 0, 14)>;
};
group2 {
psels = <NRF_PSEL(UART_RX, 0, 26)>,
<NRF_PSEL(UART_CTS, 0, 15)>;
bias-pull-up;
};
};
uart0_sleep: uart0_sleep {
group1 {
psels = <NRF_PSEL(UART_TX, 0, 27)>,
<NRF_PSEL(UART_RX, 0, 26)>,
<NRF_PSEL(UART_RTS, 0, 14)>,
<NRF_PSEL(UART_CTS, 0, 15)>;
low-power-enable;
};
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

I am setting it up like so:

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#define UART_DEV DEVICE_DT_GET(DT_NODELABEL(uart0))
static void uart_cb(const struct device *dev, struct uart_event *evt, void *user_data) {
LOG_INF("GOT UART FRAME!");
switch (evt->type) {
case UART_RX_RDY:
// do stuff (truncated)
break;
case UART_RX_DISABLED:
// RX buffer got full or RX stopped, re-enable to continue receiving
uart_rx_enable(UART_DEV, rx_buf, sizeof(rx_buf), SYS_FOREVER_MS);
break;
case UART_RX_STOPPED:
LOG_ERR("UART RX stopped unexpectedly!");
uart_rx_enable(UART_DEV, rx_buf, sizeof(rx_buf), SYS_FOREVER_MS);
break;
default:
break;
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When that uart_rx_enable() function is called, I get a SECURE FAULT:

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[00:00:09.517,822] <inf> testapp: Setting up UART...
[00:00:09.518,188] <inf> testapp: Setting up UART callback...
[00:00:09.518,554] <inf> testapp: Enabling UART transmission...
[00:00:09.521,484] <err> os: ***** SECURE FAULT *****
[00:00:09.521,850] <err> os: Invalid entry point
[00:00:09.522,216] <err> os: r0/a1: 0x00059638 r1/a2: 0x2001d333 r2/a3: 0x00000320
[00:00:09.522,796] <err> os: r3/a4: 0xffffffff r12/ip: 0x00000000 r14/lr: 0x0001e3d3
[00:00:09.523,315] <err> os: xpsr: 0x00000000
[00:00:09.523,712] <err> os: s[ 0]: 0x00000000 s[ 1]: 0x2002cc04 s[ 2]: 0x00000000 s[ 3]: 0x0004772b
[00:00:09.524,444] <err> os: s[ 4]: 0x2002cc00 s[ 5]: 0x00000002 s[ 6]: 0x00000001 s[ 7]: 0x0002e0c9
[00:00:09.525,146] <err> os: s[ 8]: 0x00000010 s[ 9]: 0x00000000 s[10]: 0x2001ce90 s[11]: 0x0003fe03
[00:00:09.525,848] <err> os: s[12]: 0x0000002a s[13]: 0x00000020 s[14]: 0x00000000 s[15]: 0x00000000
[00:00:09.526,519] <err> os: fpscr: 0x00000000
[00:00:09.526,916] <err> os: Faulting instruction address (r15/pc): 0x00000000
[00:00:09.527,374] <err> os: >>> ZEPHYR FATAL ERROR 38: Unknown error on CPU 0
[00:00:09.527,862] <err> os: Current thread: 0x20013088 (unknown)
[00:00:09.528,289] 31m<err> os: Halting system[0m
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Any ideas? I am nearly at a point now where I'm about to just switch to I2C or something else between the two MCUs.

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