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LPC11C24: select()

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This commit is contained in:
Pavel Kirienko 2014-04-16 00:05:25 +04:00
parent 09203aab1d
commit a1ea05bdea
3 changed files with 47 additions and 10 deletions
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2
libuavcan_drivers/lpc11c24/driver/include/uavcan_lpc11c24/can.hpp
View File

@ -23,7 +23,7 @@ public:
int init(uavcan::uint32_t baudrate);
bool hasPendingRx() const;
bool hasReadyRx() const;
bool hasEmptyTx() const;
bool hadActivity();

34
libuavcan_drivers/lpc11c24/driver/src/can.cpp
View File

@ -206,7 +206,7 @@ int CanDriver::init(uavcan::uint32_t baudrate)
return 0;
}
bool CanDriver::hasPendingRx() const
bool CanDriver::hasReadyRx() const
{
CriticalSectionLocker locker;
return rx_queue.getLength() > 0;
@ -291,9 +291,35 @@ uavcan::int16_t CanDriver::receive(uavcan::CanFrame& out_frame, uavcan::Monotoni
uavcan::int16_t CanDriver::select(uavcan::CanSelectMasks& inout_masks, uavcan::MonotonicTime blocking_deadline)
{
(void)inout_masks;
(void)blocking_deadline;
return -1;
const bool noblock = ((inout_masks.read == 1) && hasReadyRx()) ||
((inout_masks.write == 1) && hasEmptyTx());
if (!noblock && (clock::getMonotonic() > blocking_deadline))
{
/*
* Are you afraid of the global warming? Fear no more, the solution is right here.
*
* It's not cool (literally) to burn cycles in a busyloop, and we have no OS to pass control to other
* tasks, thus solution is to halt the core until a hardware event occurs - e.g. clock timer overflow.
* Upon such event the select() call will return, even if no requested IO operations became available.
* It's OK to do that, libuavcan can handle such behavior.
*
* Note that it is not possible to precisely control the sleep time with WFE, since we can't predict when
* the next hardware event occurs. Worst case conditions:
* - WFE gets executed right after the clock timer interrupt;
* - CAN bus is completely silent (no traffic);
* - User's application has no interrupts and generates no hardware events.
* In such scenario execution will stuck here for one period of the clock timer interrupt, even if
* blocking_deadline will expire sooner.
* If the user's application requires higher timing precision, an extra dummy IRQ can be added just to
* break WFE every once in a while.
*/
asm volatile ("wfe");
}
inout_masks.read = hasReadyRx() ? 1 : 0;
inout_masks.write = hasEmptyTx() ? 1 : 0;
return 0; // Return value doesn't matter as long as it is non-negative
}
uavcan::int16_t CanDriver::configureFilters(const uavcan::CanFilterConfig* filter_configs,

21
libuavcan_drivers/lpc11c24/test_olimex_lpc_p11c24/src/main.cpp
View File

@ -37,7 +37,12 @@ int main()
board::setErrorLed(uavcan_lpc11c24::CanDriver::instance().getErrorCount() > 0 ||
uavcan_lpc11c24::CanDriver::instance().hadActivity());
if (uavcan_lpc11c24::CanDriver::instance().hasPendingRx())
uavcan::CanSelectMasks masks;
masks.read = 1;
masks.write = 1;
uavcan_lpc11c24::CanDriver::instance().select(masks, ts_mono + uavcan::MonotonicDuration::fromMSec(10));
if (masks.read == 1)
{
board::setStatusLed(true);
uavcan::CanFrame frm;
@ -45,17 +50,23 @@ int main()
uavcan::MonotonicTime mono;
uavcan::CanIOFlags flags;
ENFORCE(1 == uavcan_lpc11c24::CanDriver::instance().receive(frm, mono, utc, flags));
asm volatile ("nop");
frm.id += 0x100;
ENFORCE(1 == uavcan_lpc11c24::CanDriver::instance().send(frm, mono, 0));
if (masks.write == 1)
{
frm.id += 0x100;
ENFORCE(1 == uavcan_lpc11c24::CanDriver::instance().send(frm, mono, 0));
}
}
else
{
board::setStatusLed(false);
}
if ((ts_mono - prev_time_pub_at).toMSec() >= 1000)
masks.read = 0;
masks.write = 1;
uavcan_lpc11c24::CanDriver::instance().select(masks, ts_mono + uavcan::MonotonicDuration::fromMSec(10));
if ((ts_mono - prev_time_pub_at).toMSec() >= 1000 && (masks.write == 1))
{
prev_time_pub_at = ts_mono;