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LPC11C24: Fixed TX priority inversion in CAN driver

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This commit is contained in:
Pavel Kirienko
2014-04-16 15:02:45 +04:00
parent c114ce8c99
commit 5926e3dd45
1 changed files with 17 additions and 20 deletions
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libuavcan_drivers/lpc11c24/driver/src/can.cpp
+17 -20
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@@ -28,12 +28,12 @@ namespace
{
/**
* Hardware message objects are allocated as follows:
* - 1..NumTxMsgObjects - TX objects
* - NumTxMsgObjects..32 - RX objects
* - 1 - Single TX object
* - 2..32 - RX objects
* TX priority is defined by the message object number, not by the CAN ID (chapter 16.7.3.5 of the user manual),
* hence we can't use more than one object because that would cause priority inversion on long transfers.
*/
const unsigned NumMsgObjects = 32;
const unsigned NumTxMsgObjects = 1;
const unsigned NumRxMsgObjects = NumMsgObjects - NumTxMsgObjects;
/**
* Total number of CAN errors.
@@ -42,10 +42,9 @@ const unsigned NumRxMsgObjects = NumMsgObjects - NumTxMsgObjects;
uint32_t error_cnt;
/**
* Message objects that are free to begin a transmission are indicated here.
* Bit 0 stands for msgobj 1, bit 1 stands for msgobj 2, etc.
* True if there's no pending TX frame, i.e. write is possible.
*/
uint32_t tx_msgobj_free_mask = (1 << NumTxMsgObjects) - 1;
bool tx_free = true;
/**
* Gets updated every time the CAN IRQ handler is being called.
@@ -167,7 +166,7 @@ int CanDriver::init(uavcan::uint32_t baudrate)
CriticalSectionLocker locker;
error_cnt = 0;
tx_msgobj_free_mask = (1 << NumTxMsgObjects) - 1;
tx_free = true;
last_irq_utc_timestamp = 0;
had_activity = false;
@@ -220,7 +219,7 @@ bool CanDriver::hasReadyRx() const
bool CanDriver::hasEmptyTx() const
{
CriticalSectionLocker locker;
return tx_msgobj_free_mask != 0;
return tx_free;
}
bool CanDriver::hadActivity()
@@ -260,19 +259,16 @@ uavcan::int16_t CanDriver::send(const uavcan::CanFrame& frame, uavcan::Monotonic
/*
* Transmission
*/
(void)tx_deadline; // TX timeouts are not supported by this driver yet.
(void)tx_deadline; // TX timeouts are not supported by this driver yet (and hardly going to be).
CriticalSectionLocker locker;
for (unsigned i = 0; i < NumTxMsgObjects; i++)
if (tx_free)
{
if (tx_msgobj_free_mask & (1 << i))
{
tx_msgobj_free_mask &= ~(1U << i); // Mark as pending - will be released in TX callback
msgobj.msgobj = i + 1;
LPC_CCAN_API->can_transmit(&msgobj);
return 1;
}
tx_free = false; // Mark as pending - will be released in TX callback
msgobj.msgobj = 1;
LPC_CCAN_API->can_transmit(&msgobj);
return 1;
}
return 0;
}
@@ -341,7 +337,7 @@ uavcan::uint64_t CanDriver::getErrorCount() const
uavcan::uint16_t CanDriver::getNumFilters() const
{
return NumRxMsgObjects;
return NumMsgObjects - 1; // First msgobj is reserved for TX frame
}
uavcan::ICanIface* CanDriver::getIface(uavcan::uint8_t iface_index)
@@ -397,7 +393,8 @@ void canRxCallback(uint8_t msg_obj_num)
void canTxCallback(uint8_t msg_obj_num)
{
uavcan_lpc11c24::tx_msgobj_free_mask |= 1U << (msg_obj_num - 1);
(void)msg_obj_num;
uavcan_lpc11c24::tx_free = true;
uavcan_lpc11c24::had_activity = true;
}