Triple buffer management APIs

Introduction

Functions
uint8_t *	PN_getPpmBuff (t_rtcPacket *pkt)
	Return a pointer to buffer indicated by NEXT This will be the next available free buffer(in the triple buffer scheme). Stack can now fill this buffer and once done call PN_relPpmBuff to indicate the PRU on new data. More...
uint8_t *	PN_relPpmBuff (PN_Handle pnHandle, t_rtcPacket *pkt)
	Swap NEXT with LAST and return new NEXT address . More...
int32_t	PN_checkLastPPM (PN_Handle pnHandle, t_rtcPacket *pkt)
	Update proc pointer in paket object and udpate descriptor if there is a new last buffer. More...
int32_t	PN_nextCpmRdy (PN_Handle pnHandle, t_rtcPacket *pkt)
	Swap CPM NEXT with LAST and set validLast flag. More...
uint8_t *	PN_getLastCpm (PN_Handle pnHandle, t_rtcPacket *pkt)
	Swap CPM LAST with PROC if validLast is true, clear validLast flag. More...
int32_t	PN_cpmBuffLock (PRUICSS_HwAttrs const *pruicssHwAttrs, uint8_t pos, buffLocks buff)
	Locks CPM Buffer indicating that ARM is consuming the particular buffer. PRU cannot write to this buffer. More...

Enumerations
enum	buffLocks { BUFF1 = 0, BUFF2, BUFF3, NOBUFF }
	Enumerates the Buffer indexes of Triple buffers. Buffer lock needs to be aligned with firmware. More...

Enumeration Type Documentation

buffLocks

enum buffLocks

Enumerates the Buffer indexes of Triple buffers. Buffer lock needs to be aligned with firmware.

Enumerator
BUFF1	Buffer Index 0
BUFF2	Buffer Index 1
BUFF3	Buffer Index 2
NOBUFF	No Buffer

Function Documentation

PN_getPpmBuff()

uint8_t* PN_getPpmBuff

(

t_rtcPacket *

pkt

)

Return a pointer to buffer indicated by NEXT
This will be the next available free buffer(in the triple buffer scheme). Stack can now fill this buffer and once done call PN_relPpmBuff to indicate the PRU on new data.

Parameters

pkt	pointer to packet object

Returns

pointer to NEXT packet buffer address

PN_relPpmBuff()

uint8_t* PN_relPpmBuff	(	PN_Handle	pnHandle,
		t_rtcPacket *	pkt
	)

Swap NEXT with LAST and return new NEXT address
.

This API is called when stack has completed updating data to the buffer received from PN_getPpmBuff. This indicates the PRU about data update and updates the ACTIVE_LIST directly. Stack can now start filling data in the NEXT buffer returned

Parameters

pnHandle	Profinet Handle
pkt	pointer to packet object

Returns

pointer to NEXT packet buffer address

PN_checkLastPPM()

int32_t PN_checkLastPPM	(	PN_Handle	pnHandle,
		t_rtcPacket *	pkt
	)

Update proc pointer in paket object and udpate descriptor if there is a new last buffer.

Called from the PN_ppmIsrHandler. The PRU firmware checks if there is a new buffer available to send by checking the validLast flag in t_rtcPacket . If available swaps the proc buffer(which is currently being send by the PRU), with the last buffer(the buffer which holds the latest data produced by the stack). This ensures that the PRU sends out latest available valid data at any point of time.

Parameters

pnHandle	Profinet Handle
pkt	pointer to packet object

Returns

1: new buffer activated
0: no buffer update <0: Not a PPM packet

PN_nextCpmRdy()

int32_t PN_nextCpmRdy	(	PN_Handle	pnHandle,
		t_rtcPacket *	pkt
	)

Swap CPM NEXT with LAST and set validLast flag.

Called from PN_cpmIsrHandler , when a new CPM frame has arrived and sets the validLast flag in t_rtcPacket . When the stack is ready to receive an updated CPM packet, it calls PN_getLastCpm and this LAST packet is consumed by the stack

Parameters

pnHandle	Profinet Handle
pkt	pointer to packet object

Return values

0	buffers swapped
1	buffers swapped and overrun detected This indicates the validLast flag was already set, and the stack has missed to consume a CPM packet
-1	error - wrong packet type

PN_getLastCpm()

uint8_t* PN_getLastCpm	(	PN_Handle	pnHandle,
		t_rtcPacket *	pkt
	)

Swap CPM LAST with PROC if validLast is true, clear validLast flag.

When the stack is ready to consume a new CPM packet, this API is called. This swaps the LAST buffer(which has the latest updated/consumed data by the PRU firmware) and the PROC buffer(which is being currently consumed by the stack). This also locks the new PROC buffer indicating that the Stack is consuming this buffer(PRU won't write to this buffer)

Parameters

[in]	pnHandle	Profinet Handle
	pkt	pointer to packet object

Returns

buffer PROC buffer address

PN_cpmBuffLock()

int32_t PN_cpmBuffLock	(	PRUICSS_HwAttrs const *	pruicssHwAttrs,
		uint8_t	pos,
		buffLocks	buff
	)

Locks CPM Buffer indicating that ARM is consuming the particular buffer. PRU cannot write to this buffer.

Parameters

[in]	pruicssHwAttrs	PRUICSS HW Attributes for base addresses
[in]	pos	CPM descriptor position Valid Range 0-7
[in]	buff	Indicates the index of Buffer Valid values for "buff" are BUFF1 - Indicating the first buffer BUFF2 - Indicating the second buffer BUFF3 - Indicating the third buffer NOBUFF - Indicates No buffer selected

Return values

0	on success
<0	if failure