Use libuarte example with GPIO

[roduss]

Good afternoon everyone,

I am facing problems using libuarte example (SDK 17 and NRF52 DK. Using SES and S132, PCA 10040)
It works well with puTTY or other software, but I want to use it to read data from an Arduino.

What I do is the following : 
I connect the RX pin to pin 8 and TX pin to pin 6 as described in the pca10040.h.
Rx is connected to the Tx pin of my Arduino (which is sending data, I can see it with the blinking LED), but I do not see any LED on with the NRF52 DK nor any response ... 

From what I've understood, whenever the nrf52 receives data, it must echo it, but it does not echo neither in Arduino, neither in puTTY. (I've understood that I need to use NRF_LOG_INFO to print using puTTY because UART was used with GPIO)

I've also tried the uart project, using flow Control, but I've been unable to receive data as well ...

Is there something that need to be changed in the example to read data with UART using the RX pin and libuarte example ?

Thanks a lot for your answer,

Roduss

[ovrebekk]

Hi Roduss

The example should work fine as long as the UART signals are routed correctly, and the voltage levels are compatible. 

Are you saying you don't even get the echoing to work even when using the DK alone, without connecting any external boards?

One thing to keep in mind when connecting an external UART is that pins 6 and 8 already have a connection to the programming chip on the DK, which is how it gets connected to the virtual J-Link comport. When connecting to an external board you might have to change to some other pins, or break the SB22, SB23, SB24 and SB25 solder bridges to break the connection between the programming chip and the nRF52832. 

Best regards
Torbjørn

[roduss]

Good afternoon,
Thanks for your quick answer !
If I use the DK alone, I get the echo via puTTY, this is working.
What I want is to send a signal using UART protocol with my Arduino (5V) and receive it with the DK. (And when I receive data, print it to puTTY or make a LED blinking)
The Arduino can send a start bit/ a stop bit or even Flow Control if necessary.

So, when you're saying
UART is that pins 6 and 8 already have a connection to the programming chip on the DK, which is how it gets connected to the virtual J-Link comport

Is this related to ?

So, a solution to make the libuarte example work could be :

• Connect the Tx of the Arduino to a random pin of the DK (let's say pin 20 will be RX)
• Connect the Rx of the Arduino to another pin of the DK (pin 21 will be TX)
• Change anything of this function (or the definition of the RX/TX pins picture above) to initialize pin 20 and 21 as RX and TX? (function is from main.c)
  
• Change anything to see the data being echoed in puTTY when received ?

Thanks a lot for your help !

[ovrebekk]

Hi 

If your Arduino board is running at 5V it won't be compatible with the nRF52DK, which typically runs at ~3V. 

You would need some kind of level shifter on the UART signals: Either by using a dedicated level shifter IC, or making something more simple based on the fact that the signals are one directional (a 5V to 3V level shifter might be implemented by a simple voltage divider, while 3V to 5V could be implemented with some transistors). 

Best regards
Torbjørn

[roduss]

Hi,

Ooops my bad ! So I changed my wiring to send 3.3V to the nRF DK, but still, I don't get the fundamentals ...
How should I wire my RX/TX with the DK to see data from Arduino ?

As you said, pin 6 and 8 are used, so I tried to use pin 11 & 12 (TX and RX), initialize them like this : 

#define TX_PIN 11 
#define RX_PIN 12

void gpio_init(void)
{
  nrf_gpio_cfg_input(RX_PIN, NRF_GPIO_PIN_NOPULL);
  nrf_gpio_cfg_output(TX_PIN);
}

And used them in the libuarte config function  :

nrf_libuarte_async_config_t nrf_libuarte_async_config = {
            .tx_pin     = TX_PIN,
            .rx_pin     = RX_PIN,
            .baudrate   = NRF_UARTE_BAUDRATE_115200,
            .parity     = NRF_UARTE_PARITY_EXCLUDED,
            .hwfc       = NRF_UARTE_HWFC_DISABLED,
            .timeout_us = 100,
            .int_prio   = APP_IRQ_PRIORITY_LOW
    };

But didn't read nothing ...
What am I missing ? Should I use another example ? 

[ovrebekk]

Hi 

There is no need to manually call the nrf_gpio_cfg_xxx functions when using libuarte. When you enable the UART the pin configuration will be overridden by the UART module. 

I was able to move the TX and RX to pin 11 and 12 simply by changing the .tx_pin and .rx_pin defines in the libuarte config struct. 

I tested it just to be sure, by connecting pin 11 and 12 on one kit to pin 6 and 8 on another kit (in order to connect these pins to a PC through the Segger chip on the second kit). 

Are you still having issues with it?

Best regards
Torbjørn