nRF51822 doesn't start if UART RX pin is connected

RE: nRF51822 doesn't start if UART RX pin is connected

Ole Bauck — Mon, 09 Jan 2017 10:06:18 GMT

It is normally not compulsory with a pull-up on the UART RX pin, but looking at the datasheet of the STN1110 it is in this case:

UART_TX
UART transmit output. Open drain – requires a pull-up
to VDD or +5V (4 mA max). Pull-up value depends on
UART baud rate and the trace length (higher resistor
values can be used with lower baud rates and shorter
traces); typical value is 4.7 kΩ.

This is probably to support multiple voltage levels.

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Tue, 27 Dec 2016 05:10:05 GMT

It is working with no code change, but i added a 10K pullup resistor at RX of nRF51822, is it compulsory to connect a pullup resistor at RX of uart?

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Fri, 23 Dec 2016 11:09:13 GMT

@Ole Bauck As u have answered here i tried the modified app_uart_fifo.c but still didn't fixed.

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Fri, 23 Dec 2016 10:58:35 GMT

In uart handler in event APP_UART_COMMUNICATION_ERROR there is a error handler(APP_ERROR_HANDLER) macro this macro is making difference, if i comment this macro the device starts advertising and the program runs fine, but the problem is i cant receive data at uart rx, if i keep that macro the program restarts after calling function sd_softdevice_enable.

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Thu, 22 Dec 2016 11:26:08 GMT

error code is 0x0C not 0x04.

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Thu, 22 Dec 2016 11:07:14 GMT

the processor restarts immediately after calling sd_softdevice_enable, breakpoint hit will not occur at line where the return value of sd_softdevice_enable is checked.

RE: nRF51822 doesn't start if UART RX pin is connected

Ole Bauck — Thu, 22 Dec 2016 11:01:05 GMT

If sd_softdevice_enable returns , what is the error code?

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Thu, 22 Dec 2016 10:55:33 GMT

I found the error parameters. error code is 0x04, m_line_num is 0x01F3 and m_p_file_name is 0x01E6B4

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Thu, 22 Dec 2016 10:33:41 GMT

Yes iam using uart driver from SDK, uart code is same has that of ble_app_uart example code. What causes that error. how should i overcome it.

RE: nRF51822 doesn't start if UART RX pin is connected

Ole Bauck — Thu, 22 Dec 2016 09:43:06 GMT

The default configuration for the SDK examples is that they will reset when the code meets an error condition, see here. So probably the sd_softdevice_enable function returns an error. Check if this is the case and what the error code is.

Are you using the uart driver from the SDK (app_uart_fifo)?

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Thu, 22 Dec 2016 05:32:01 GMT

for calling SOFTDEVICE_HANDLER_INIT iam using "NRF_CLOCK_LFCLKSRC_XTAL_20_PPM" as clock source.

RE: nRF51822 doesn't start if UART RX pin is connected

sunil kumar — Thu, 22 Dec 2016 05:30:37 GMT

I correct myself, the processor starts but it restarts while initializing softdevice, in softdevice_handler_init() function the breakpoint at function sd_softdevice_enable() will hit, after this function the processor will restart. The voltage at Tx of STN1110 is 0.7V and at PSU for nRF is 3.3V.

RE: nRF51822 doesn't start if UART RX pin is connected

Alex — Wed, 21 Dec 2016 15:19:19 GMT

When disconnected, what is the voltage on Tx of STN1110 and what is voltage of PSU for nRF?