How to use send and receive serial data over gpio pins?

[Ajay Karthik]

Hi,

I am stuck in sending and receiving serial data over Rx and Tx in nrf51 DK. I used arduino to prototype a fingerprint access control system. Now I am shifting to nrf51 using 12.3 SDK, It was easy to send and receive serial data over Rx and Tx in arduino using Software Serial. How to do it in nrf51? the baud rate for fingerprint sensor is different from the ble_app_uart example. The sensor uses 9600 baud rate ,UART (TLL logical level) and for communication uses data package array of size 11-14 bytes to send and receive communication, for example the format is

Could I get help in tools or advice to do this in nrf51?

[Jørgen Holmefjord]

Hi,

Is there any specific reasons you want to use software serial? The UART peripheral of nRF51 series support baudrates of 9600 (and lower). Please have a look at the reference manual.

Best regards.
Jørgen

[daverv]

Hi,

Is there any particular reason why not to use SoftwareSerial ?

I'm trying to establish two way communications between an nrf51 and an arduino using software serial and uart.

What I'm seeing is that I send 20 bytes from arduino but the nrf51 doesn't receive them all. And if I sent only one byte from arduino, the nrf51 seams to receive 4 bytes. 

If I send 20 bytes from nrf51 to arduino, arduino receives them well, but not the other way around.

 Edit: I've tried this with 1200, 2400 and 9600 baud rates.

[Jørgen Holmefjord]

Software serial requires the CPU to be available to read/write the GPIOs at the exact time that the bits are received. In a single-core BLE SoC like the nRF51, the CPU will always have highest priority to handle timing-critical events. The UART peripheral in nRF51 series ICs has a built-in HW FIFO that allows you to receive up to 6 bytes without CPU intervention.

You may be able to do those low baudrates with bit-banging/software serial, but there is no guarantee that it will work. I would rather recommend using the HW UART peripheral for supported baudrates.