When initializing serial disable all interrupts as some of these may
have been enabled by a bootloader. This ensures that the NRF52
serial driver remains compatible with any bootloader version.
Make the following enhancement:
-Support serial port use without flow control
-Prevent dropped bytes by updating flow control handling
-Remove dead code
Serial port use without flow control:
In the prior implementation there was a window of time between
reloading DMA buffers after a timeout where bytes could be dropped.
This is because the uart needed to be turned off in order to flush the
bytes in the DMA buffer.
This change configures the DMA buffer to only receive one byte at a
time so there is no need to disable the uart to flush it. After each
byte is received the DMA transfer will be over so the transfer will
never be partially complete and need flushing. Since the uart is
always on it is safe to use it even without flow control.
Prevent dropped bytes by updating flow control handling:
To prevent dropped bytes due to high latency the flow control handling
of the RTS line was configured to be asserted automatically by
hardware after each byte. Once the CPU has read the byte and setup
the next receive buffer the RTS line is deasserted to the transfer can
continue. This ensure that when flow control is enabled data won't be
lost due to interrupt latency.
Remove dead code:
With the above changes there is a lot of dead code, such as the timer
handling code. This patch removes the code that is no longer used.
Busy-wait before sending a charecter instead of after. If
serial_writeable has been called first, the busy-wait loop will
be skipped.
Added initialization code to ensure NRF_UARTE_EVENT_TXDRDY is
armed correctly.
In nordic_nrf5_uart_event_handler if the events NRF_UARTE_EVENT_ENDRX
and NRF_UARTE_EVENT_RXSTARTED become pending after the check for
NRF_UARTE_EVENT_ENDRX but before the check for
NRF_UARTE_EVENT_RXSTARTED the RX DMA buffers will be setup incorrectly
by nordic_nrf5_uart_event_handler_rxstarted because active_bank hasn't
been updated. This cause dropped and incorrect data.
This patch fixes that problem by adding a second check for
NRF_UARTE_EVENT_ENDRX after checking for NRF_UARTE_EVENT_RXSTARTED
and skipping processing if NRF_UARTE_EVENT_ENDRX is set. The
subsequent interrupt will process both in the correct order. This
ensures that these events cannot be handled out of order and thus fixes
the corruption.
Due to buggy flow control logic in the UARTE, the stop signal
is not being set as it is supposed to when the the module is
not ready to receive data.
This commit signals the sender to halt transmitting when a DMA
buffer is full and only continue again when the atomic FIFO
buffer has been emptied. This allows platforms with hardware
flow control to minimize all buffers and rely on flow control
instead.
The preprocessor based macro check #if evaluates all
enums as 0 and hence the code does not get compiled.
Since move this to a runtime check where the pin variable
can be correctly evaluated.
Delete mbed_overrides.c as it has a target specific mbed_sdk_init() to
resolve linking problem.
This is a follow on patch to:
https://github.com/ARMmbed/mbed-os/pull/8046
While investigating the RX issue on NRF52_DK after SDK 14 updates,
it is observed that the RX FIFO doesn't get filled up, when the
flow control is disabled. Hence the readable never returns true.
If using Serial interface, the stdio file handles (0, 1, 2) get opened.
This results in configuring the flow control for STDIO, and it is observed
that the RX FIFO gets filled.
However, if RawSerial is used, the STDIO file handles
don't get opened. During the debug process it was observed that if the
flow control is configured once and then set to disabled, RX worked
as expected.
Alternative to this approach is that user application specifically
enables flow control as done in mbed's Greentea test suite. See https://goo.gl/r8nBYH
See https://goo.gl/8VB2qg step 14 for _initio's description.
See test code to reproduce the issue and test fix here: https://goo.gl/AQU1xG
Description
The change in behavior with NRF52's UART RX is documented here. #6891
This change is a fix for the above issue.
--legacyalign, --no_legacyalign are deprecated from ARMC6 compiler, in order to
remove deprecated flags all linker files (GCC and IAR as well to have uniformity)
should strictly align to 8-byte boundary
While investigating the RX issue on NRF52_DK after SDK 14 updates,
it is observed that the RX FIFO doesn't get filled up, when the
flow control is disabled. Hence the readable never returns true.
If using Serial interface, the stdio file handles (0, 1, 2) get opened.
This results in configuring the flow control for STDIO, and it is observed
that the RX FIFO gets filled.
However, if RawSerial is used, the STDIO file handles
don't get opened. During the debug process it was observed that if the
flow control is configured once and then set to disabled, RX worked
as expected.
Alternative to this approach is that user application specifically
enables flow control as done in mbed's Greentea test suite. See https://goo.gl/r8nBYH
See https://goo.gl/8VB2qg step 14 for _initio's description.
See test code to reproduce the issue and test fix here: https://goo.gl/AQU1xG
Description
The change in behavior with NRF52's UART RX is documented here. #6891
This change is a fix for the above issue.
There are scenarios where putc is called within a critical section, e.g
to log ASSERTs in early initialization code. The interrupts being
disabled here prevents the handlers for the UARTE from executing.
This breaks the tx_in_progress flag based approach. The tx_in_progress
never gets reset. Poll on the TXDRDY instead.
It can be recreated with a simple program as shown here:
*************** Current Behavior ****************
++ MbedOS Error Info ++
Error Status: 0x80FF0100 Code: 256 Module: 255
Error Message: F
************** With Fix *************************
++ MbedOS Error Info ++
Error Status: 0x80FF0100 Code: 256 Module: 255
Error Message: Fatal Run-time error
Location: 0x2C0A9
Error Value: 0x0
Current Thread: Id: 0x20005520 Entry: 0x30EBF StackSize: 0x1000 StackMem: 0x20004520 SP: 0x20005490
For more info, visit: https://armmbed.github.io/mbedos-error/?error=0x80FF0100
-- MbedOS Error Info --
nrf failure at .\main.cpp:22
***************************************************
Martin Kojtal
Russ Butler
Russ Butler
Marcus Chang
Senthil Ramakrishnan
Ashok Rao
David Saada
Naveen Kaje
Cruz Monrreal
Deepika
Andrew Leech
Yossi Levy
Jammu Kekkonen
Maciej Bocianski
Martin Kojtal