Cannot Receive data using UARTE with nRF52832

[sycra.jonathan]

Hi everyone,

I'm now using nRF52832 to communicate with a device using UARTE.

In my application, i need to constantly send a control packet to the device, to keep it responsive to the control (~15ms between each data).

I don't want my application to be blocked, so i decide to use UARTE to do it automatically, and the TX part is working perfectly.

But the RX part is just not working at all, there are two issues:

1. With a valid waveform observed on the oscilloscope, the UARTE library returns framing error.

The RX buffer is filled with the data, while the RX byte count in i) p_event->data.error.rxtx.bytes and ii) p_event->data.rxtx.bytes are zero.

2. With a valid waveform observed on the oscilloscope, the UARTE library will not returns any event. The RX buffer receives nothing.

Here is the setting of the UARTE:

    /* Init UART  */
    nrf_drv_uart_config_t config = 
    {
        .pseltxd = TX_PIN,
        .pselrxd = RX_PIN,
        .pselcts = NRF_UART_PSEL_DISCONNECTED,
        .pselrts = NRF_UART_PSEL_DISCONNECTED,
        .p_context = NULL,
        .hwfc = NRF_UART_HWFC_DISABLED,
        .parity = NRF_UART_PARITY_EXCLUDED,
        .baudrate = NRF_UART_BAUDRATE_250000,
        .interrupt_priority = UART_DEFAULT_CONFIG_IRQ_PRIORITY,
    };

    err_code = nrf_drv_uart_init(&uart_inst, &config, uart_event_handler);

Here is how i start the RX task:

nrf_drv_uart_rx(&uart_inst, rev_handler.rev_buf, rev_handler.rx_len);

Here is the SDK config setting:

// <e> NRFX_PRS_ENABLED - nrfx_prs - Peripheral Resource Sharing module
//==========================================================
#ifndef NRFX_PRS_ENABLED
#define NRFX_PRS_ENABLED 1
#endif
// <q> NRFX_PRS_BOX_0_ENABLED  - Enables box 0 in the module.
 

#ifndef NRFX_PRS_BOX_0_ENABLED
#define NRFX_PRS_BOX_0_ENABLED 0
#endif

// <q> NRFX_PRS_BOX_1_ENABLED  - Enables box 1 in the module.
 

#ifndef NRFX_PRS_BOX_1_ENABLED
#define NRFX_PRS_BOX_1_ENABLED 0
#endif

// <q> NRFX_PRS_BOX_2_ENABLED  - Enables box 2 in the module.
 

#ifndef NRFX_PRS_BOX_2_ENABLED
#define NRFX_PRS_BOX_2_ENABLED 0
#endif

// <q> NRFX_PRS_BOX_3_ENABLED  - Enables box 3 in the module.
 

#ifndef NRFX_PRS_BOX_3_ENABLED
#define NRFX_PRS_BOX_3_ENABLED 0
#endif

// <q> NRFX_PRS_BOX_4_ENABLED  - Enables box 4 in the module.
 

#ifndef NRFX_PRS_BOX_4_ENABLED
#define NRFX_PRS_BOX_4_ENABLED 1
#endif

// <e> NRFX_PRS_CONFIG_LOG_ENABLED - Enables logging in the module.
//==========================================================
#ifndef NRFX_PRS_CONFIG_LOG_ENABLED
#define NRFX_PRS_CONFIG_LOG_ENABLED 0
#endif
// <o> NRFX_PRS_CONFIG_LOG_LEVEL  - Default Severity level
 
// <0=> Off 
// <1=> Error 
// <2=> Warning 
// <3=> Info 
// <4=> Debug 

#ifndef NRFX_PRS_CONFIG_LOG_LEVEL
#define NRFX_PRS_CONFIG_LOG_LEVEL 3
#endif

// <o> NRFX_PRS_CONFIG_INFO_COLOR  - ANSI escape code prefix.
 
// <0=> Default 
// <1=> Black 
// <2=> Red 
// <3=> Green 
// <4=> Yellow 
// <5=> Blue 
// <6=> Magenta 
// <7=> Cyan 
// <8=> White 

#ifndef NRFX_PRS_CONFIG_INFO_COLOR
#define NRFX_PRS_CONFIG_INFO_COLOR 0
#endif

// <o> NRFX_PRS_CONFIG_DEBUG_COLOR  - ANSI escape code prefix.
 
// <0=> Default 
// <1=> Black 
// <2=> Red 
// <3=> Green 
// <4=> Yellow 
// <5=> Blue 
// <6=> Magenta 
// <7=> Cyan 
// <8=> White 

#ifndef NRFX_PRS_CONFIG_DEBUG_COLOR
#define NRFX_PRS_CONFIG_DEBUG_COLOR 0
#endif

// </e>

// </e>

// <e> NRFX_UARTE_ENABLED - nrfx_uarte - UARTE peripheral driver
//==========================================================
#ifndef NRFX_UARTE_ENABLED
#define NRFX_UARTE_ENABLED 1
#endif
// <o> NRFX_UARTE0_ENABLED - Enable UARTE0 instance
#ifndef NRFX_UARTE0_ENABLED
#define NRFX_UARTE0_ENABLED 0
#endif

// <o> NRFX_UARTE_DEFAULT_CONFIG_HWFC  - Hardware Flow Control

// <0=> Disabled
// <1=> Enabled

#ifndef NRFX_UARTE_DEFAULT_CONFIG_HWFC
#define NRFX_UARTE_DEFAULT_CONFIG_HWFC 0
#endif

// <o> NRFX_UARTE_DEFAULT_CONFIG_PARITY  - Parity

// <0=> Excluded
// <14=> Included

#ifndef NRFX_UARTE_DEFAULT_CONFIG_PARITY
#define NRFX_UARTE_DEFAULT_CONFIG_PARITY 0
#endif

// <o> NRFX_UARTE_DEFAULT_CONFIG_BAUDRATE  - Default Baudrate

// <323584=> 1200 baud
// <643072=> 2400 baud
// <1290240=> 4800 baud
// <2576384=> 9600 baud
// <3862528=> 14400 baud
// <5152768=> 19200 baud
// <7716864=> 28800 baud
// <8388608=> 31250 baud
// <10289152=> 38400 baud
// <15007744=> 56000 baud
// <15400960=> 57600 baud
// <20615168=> 76800 baud
// <30801920=> 115200 baud
// <61865984=> 230400 baud
// <67108864=> 250000 baud
// <121634816=> 460800 baud
// <251658240=> 921600 baud
// <268435456=> 1000000 baud

#ifndef NRFX_UARTE_DEFAULT_CONFIG_BAUDRATE
#define NRFX_UARTE_DEFAULT_CONFIG_BAUDRATE 30801920
#endif

// <o> NRFX_UARTE_DEFAULT_CONFIG_IRQ_PRIORITY  - Interrupt priority

// <0=> 0 (highest)
// <1=> 1
// <2=> 2
// <3=> 3
// <4=> 4
// <5=> 5
// <6=> 6
// <7=> 7

#ifndef NRFX_UARTE_DEFAULT_CONFIG_IRQ_PRIORITY
#define NRFX_UARTE_DEFAULT_CONFIG_IRQ_PRIORITY 6
#endif

// <e> NRFX_UARTE_CONFIG_LOG_ENABLED - Enables logging in the module.
//==========================================================
#ifndef NRFX_UARTE_CONFIG_LOG_ENABLED
#define NRFX_UARTE_CONFIG_LOG_ENABLED 0
#endif
// <o> NRFX_UARTE_CONFIG_LOG_LEVEL  - Default Severity level

// <0=> Off
// <1=> Error
// <2=> Warning
// <3=> Info
// <4=> Debug

#ifndef NRFX_UARTE_CONFIG_LOG_LEVEL
#define NRFX_UARTE_CONFIG_LOG_LEVEL 3
#endif

// <o> NRFX_UARTE_CONFIG_INFO_COLOR  - ANSI escape code prefix.

// <0=> Default
// <1=> Black
// <2=> Red
// <3=> Green
// <4=> Yellow
// <5=> Blue
// <6=> Magenta
// <7=> Cyan
// <8=> White

#ifndef NRFX_UARTE_CONFIG_INFO_COLOR
#define NRFX_UARTE_CONFIG_INFO_COLOR 0
#endif

// <o> NRFX_UARTE_CONFIG_DEBUG_COLOR  - ANSI escape code prefix.

// <0=> Default
// <1=> Black
// <2=> Red
// <3=> Green
// <4=> Yellow
// <5=> Blue
// <6=> Magenta
// <7=> Cyan
// <8=> White

#ifndef NRFX_UARTE_CONFIG_DEBUG_COLOR
#define NRFX_UARTE_CONFIG_DEBUG_COLOR 0
#endif

// </e>

// </e>

// <e> NRFX_UART_ENABLED - nrfx_uart - UART peripheral driver
//==========================================================
#ifndef NRFX_UART_ENABLED
#define NRFX_UART_ENABLED 0
#endif
// <o> NRFX_UART0_ENABLED - Enable UART0 instance
#ifndef NRFX_UART0_ENABLED
#define NRFX_UART0_ENABLED 0
#endif

// <o> NRFX_UART_DEFAULT_CONFIG_HWFC  - Hardware Flow Control

// <0=> Disabled
// <1=> Enabled

#ifndef NRFX_UART_DEFAULT_CONFIG_HWFC
#define NRFX_UART_DEFAULT_CONFIG_HWFC 0
#endif

// <o> NRFX_UART_DEFAULT_CONFIG_PARITY  - Parity

// <0=> Excluded
// <14=> Included

#ifndef NRFX_UART_DEFAULT_CONFIG_PARITY
#define NRFX_UART_DEFAULT_CONFIG_PARITY 0
#endif

// <o> NRFX_UART_DEFAULT_CONFIG_BAUDRATE  - Default Baudrate

// <323584=> 1200 baud
// <643072=> 2400 baud
// <1290240=> 4800 baud
// <2576384=> 9600 baud
// <3866624=> 14400 baud
// <5152768=> 19200 baud
// <7729152=> 28800 baud
// <8388608=> 31250 baud
// <10309632=> 38400 baud
// <15007744=> 56000 baud
// <15462400=> 57600 baud
// <20615168=> 76800 baud
// <30924800=> 115200 baud
// <61845504=> 230400 baud
// <67108864=> 250000 baud
// <123695104=> 460800 baud
// <247386112=> 921600 baud
// <268435456=> 1000000 baud

#ifndef NRFX_UART_DEFAULT_CONFIG_BAUDRATE
#define NRFX_UART_DEFAULT_CONFIG_BAUDRATE 30924800
#endif

// <o> NRFX_UART_DEFAULT_CONFIG_IRQ_PRIORITY  - Interrupt priority

// <0=> 0 (highest)
// <1=> 1
// <2=> 2
// <3=> 3
// <4=> 4
// <5=> 5
// <6=> 6
// <7=> 7

#ifndef NRFX_UART_DEFAULT_CONFIG_IRQ_PRIORITY
#define NRFX_UART_DEFAULT_CONFIG_IRQ_PRIORITY 6
#endif

// <e> NRFX_UART_CONFIG_LOG_ENABLED - Enables logging in the module.
//==========================================================
#ifndef NRFX_UART_CONFIG_LOG_ENABLED
#define NRFX_UART_CONFIG_LOG_ENABLED 0
#endif
// <o> NRFX_UART_CONFIG_LOG_LEVEL  - Default Severity level

// <0=> Off
// <1=> Error
// <2=> Warning
// <3=> Info
// <4=> Debug

#ifndef NRFX_UART_CONFIG_LOG_LEVEL
#define NRFX_UART_CONFIG_LOG_LEVEL 3
#endif

// <o> NRFX_UART_CONFIG_INFO_COLOR  - ANSI escape code prefix.

// <0=> Default
// <1=> Black
// <2=> Red
// <3=> Green
// <4=> Yellow
// <5=> Blue
// <6=> Magenta
// <7=> Cyan
// <8=> White

#ifndef NRFX_UART_CONFIG_INFO_COLOR
#define NRFX_UART_CONFIG_INFO_COLOR 0
#endif

// <o> NRFX_UART_CONFIG_DEBUG_COLOR  - ANSI escape code prefix.

// <0=> Default
// <1=> Black
// <2=> Red
// <3=> Green
// <4=> Yellow
// <5=> Blue
// <6=> Magenta
// <7=> Cyan
// <8=> White

#ifndef NRFX_UART_CONFIG_DEBUG_COLOR
#define NRFX_UART_CONFIG_DEBUG_COLOR 0
#endif

// </e>

// </e>

// <e> UART_ENABLED - nrf_drv_uart - UART/UARTE peripheral driver - legacy layer
//==========================================================
#ifndef UART_ENABLED
#define UART_ENABLED 1
#endif
// <o> UART_DEFAULT_CONFIG_HWFC  - Hardware Flow Control

// <0=> Disabled
// <1=> Enabled

#ifndef UART_DEFAULT_CONFIG_HWFC
#define UART_DEFAULT_CONFIG_HWFC 0
#endif

// <o> UART_DEFAULT_CONFIG_PARITY  - Parity

// <0=> Excluded
// <14=> Included

#ifndef UART_DEFAULT_CONFIG_PARITY
#define UART_DEFAULT_CONFIG_PARITY 0
#endif

// <o> UART_DEFAULT_CONFIG_BAUDRATE  - Default Baudrate

// <323584=> 1200 baud
// <643072=> 2400 baud
// <1290240=> 4800 baud
// <2576384=> 9600 baud
// <3862528=> 14400 baud
// <5152768=> 19200 baud
// <7716864=> 28800 baud
// <10289152=> 38400 baud
// <15400960=> 57600 baud
// <20615168=> 76800 baud
// <30801920=> 115200 baud
// <61865984=> 230400 baud
// <67108864=> 250000 baud
// <121634816=> 460800 baud
// <251658240=> 921600 baud
// <268435456=> 1000000 baud

#ifndef UART_DEFAULT_CONFIG_BAUDRATE
#define UART_DEFAULT_CONFIG_BAUDRATE 30801920
#endif

// <o> UART_DEFAULT_CONFIG_IRQ_PRIORITY  - Interrupt priority


// <i> Priorities 0,2 (nRF51) and 0,1,4,5 (nRF52) are reserved for SoftDevice
// <0=> 0 (highest)
// <1=> 1
// <2=> 2
// <3=> 3
// <4=> 4
// <5=> 5
// <6=> 6
// <7=> 7

#ifndef UART_DEFAULT_CONFIG_IRQ_PRIORITY
#define UART_DEFAULT_CONFIG_IRQ_PRIORITY 6
#endif

// <q> UART_EASY_DMA_SUPPORT  - Driver supporting EasyDMA


#ifndef UART_EASY_DMA_SUPPORT
#define UART_EASY_DMA_SUPPORT 1
#endif

// <q> UART_LEGACY_SUPPORT  - Driver supporting Legacy mode


#ifndef UART_LEGACY_SUPPORT
#define UART_LEGACY_SUPPORT 0
#endif

// <e> UART0_ENABLED - Enable UART0 instance
//==========================================================
#ifndef UART0_ENABLED
#define UART0_ENABLED 1
#endif
// <q> UART0_CONFIG_USE_EASY_DMA  - Default setting for using EasyDMA


#ifndef UART0_CONFIG_USE_EASY_DMA
#define UART0_CONFIG_USE_EASY_DMA 1
#endif

// </e>

// </e>

Please share your experience if you had the same issues to me, thank you!!

BR,

Jonathan

[Hung Bui]

Hi Jonathan, 

How big is the size of the rx buffer ? (rx_len) ? 
Please be aware that even though there is variable rxtx.bytes, it's not possible to count the number of byte received. You only receive the number of bytes in your rx buffer (rx_len) when all bytes are received (event NRFX_UARTE_EVT_RX_DONE). This is due to the limitation of the UARTE hardware that there is no register keeping track of number of bytes currently arrived. 

To solve this issue we have made a new and more advanced UART library. This library allow you to query the number of bytes received and also have a timeout if not all the bytes are arrived. Please have a look here.
The example for it is at \examples\peripheral\libuarte

[sycra.jonathan]

Hi Hung Bui,

Thanks for your reply. I have defined a 64 bytes RX buffer, and the payload i need to receive is max. 30 bytes.

The device only replies upon request from nRF52, so it is unlikely that the buffer will overflow.

My problem is UARTE cannot receive data or have framing error with a valid UART waveform.

How does libuarte help to solve the problem? Is there any bug fix or improvement compared to the old nrfx_uarte library?

I did compare the libuarte & nrfx_uarte library.

I found that in libuarte, it will initialize the events in the following sequence:

nrf_uarte_event_clear(p_libuarte->uarte, NRF_UARTE_EVENT_ENDRX);
nrf_uarte_event_clear(p_libuarte->uarte, NRF_UARTE_EVENT_RXSTARTED);
nrf_uarte_task_trigger(p_libuarte->uarte, NRF_UARTE_TASK_STARTRX);

In nrfx_uarte library, it initializes the events in this way:

nrf_uarte_event_clear(p_instance->p_reg, NRF_UARTE_EVENT_ENDRX);
nrf_uarte_event_clear(p_instance->p_reg, NRF_UARTE_EVENT_RXTO);
nrf_uarte_task_trigger(p_instance->p_reg, NRF_UARTE_TASK_STARTRX);

Is it the reason why i cannot receive data with UARTE?

BR,

Jonathan

[Hung Bui]

The libuarte wouldn't solve the issue if it's at lower level (as I mentioned, it's more on the higher level where you can have a time out and can check how many bytes received). 

I would suggest you to test with the simple uart example in \examples\peripheral\uart to check if it work. You can also test using the loop back option the provided in the code. 

[sycra.jonathan]

Finally i found that the device would return with a BREAK before the data.

I was focusing on the data part and overlook the BREAK in the waveform.

After i handled the BREAK, the UARTE RX driver works perfectly!

Thanks for your help.

[Hung Bui]

Sounds great Jonathan. I would suggest to use a Logic analyzer when debugging UART (or other digital signals) it can analyze the protocol and most likely can catch the BREAK signal.