[TARGET_NRF5] serial_api.c doesn't seem to support a platform which CTS pin are not used

[ytsuboi]

Problem

The TY51822R3 platform use nRF51822 (Rev.3) device and CTS/RTS signals are not connected to the mbed interface chip on this platform.
When printf() function is called by mbed program, the program hangs most of time.

Thoughts

I am investing this problem now. But the code in TARGET_NRF5/erial_api.c assumes flow control by CTS/RTS. It should take care about non flow control platform as well.

[ytsuboi]

It hangs at https://github.com/ARMmbed/mbed-os/blob/master/hal/targets/hal/TARGET_NORDIC/TARGET_NRF5/serial_api.c#L290 and https://github.com/ARMmbed/mbed-os/blob/master/hal/targets/hal/TARGET_NORDIC/TARGET_NRF5/serial_api.c#L488

[ytsuboi]

Patched. Now, printf() works fine on TY51822r3. Still need to test on nRF51-DK.
ytsuboi@0b79028

Can I make a pull request after testing with nRF51-DK? @anangl @0xc0170

[ytsuboi]

PR made. #2482

[nuket]

This hang is also biting me hard on the nRF51-DK.

[ytsuboi]

#2489

[sg-]

Can you confirm is #2535 resolved this issue?

[ytsuboi]

PR made #2555

[nvlsianpu]

@ytsuboi Could you close this issue?

[ytsuboi]

Solved! @nvlsianpu