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feat: automatic CAN filter configuration #20

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feat: automatic CAN filter configuration #20

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6a99af9
Add ID List CAN ID Filter in rtcan_start()
rureverek May 3, 2023
f46f187
Fix comments
rureverek May 3, 2023
b555b35
Add constants, for each hash entry look for chained nodes
rureverek May 3, 2023
9e4126c
Alternate filter assignment between both FIFOs
rureverek May 4, 2023
3008cd3
Add limit (NUM_FILTERS * NUM_IDS_PER_FILTER) to the can id finder loop
rureverek May 4, 2023
ae80c5e
Move the filter configuration to rtcan_subscribe()
rureverek May 10, 2023
aaf21fd
Fix can_ids
rureverek May 10, 2023
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Add ID List CAN ID Filter in rtcan_start()
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@rureverek
rureverek committed May 3, 2023
commit 6a99af9b6c22c003a34b32f0512224dff65ba82e
68 changes: 48 additions & 20 deletions src/rtcan.c
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Original file line number Diff line number Diff line change
Expand Up @@ -179,26 +179,6 @@ rtcan_status_t rtcan_init(rtcan_handle_t* rtcan_h,
ADD_ERROR_IF(tx_status != TX_SUCCESS, RTCAN_ERROR_INTERNAL, rtcan_h);
}

// TODO: configure CAN filters
if (no_errors(rtcan_h))
{
CAN_FilterTypeDef filter;
filter.FilterActivation = ENABLE;
filter.FilterFIFOAssignment = CAN_FILTER_FIFO0;
filter.FilterIdHigh = 0x0000 << 5U;
filter.FilterIdLow = 0x0000 << 5U;
filter.FilterMaskIdHigh = 0x0000 << 5U;
filter.FilterMaskIdLow = 0x0000 << 5U;
filter.FilterMode = CAN_FILTERMODE_IDMASK;
filter.FilterScale = CAN_FILTERSCALE_16BIT;
filter.FilterBank = 0;

HAL_StatusTypeDef hal_status = HAL_CAN_ConfigFilter(rtcan_h->hcan,
&filter);

ADD_ERROR_IF(hal_status != HAL_OK, RTCAN_ERROR_INIT, rtcan_h);
}

return create_status(rtcan_h);
}

Expand All @@ -209,6 +189,54 @@ rtcan_status_t rtcan_init(rtcan_handle_t* rtcan_h,
*/
rtcan_status_t rtcan_start(rtcan_handle_t* rtcan_h)
{
/* Since the subscriber ID list is known, we can configure the CAN ID Filter now */

uint32_t can_id_list[RTCAN_HASHMAP_SIZE] = {0};
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Perhaps counterintuitively there can be more subscribers than hashmap entries, so I think the size of this array should be replaced with something like NUM_IDS_PER_FILTER * NUM_FILTERS.

The reason there can be more subscribers than hashmap entries is that when two IDs result in a hash collision (same hash for different CAN ID), they are combined in that hashmap entry as a singly linked list using "separate chaining" (there are some notes in the docs folder about this implementation). The actual subscribers are allocated from a memory pool, which is ultimately what determines the maximum number of subscriptions.

int number_ids = 0;

/* Save and count all CAN IDs stored in hashmap */
for (uint32_t i = 0; i < RTCAN_HASHMAP_SIZE; i++)
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Loop iteration limit should be sizeof(can_id_list) / sizeof(uint32_t) or NUM_FILTERS * NUM_IDS_PER_FILTER. If you want to go for the second, I might make a new constant TOTAL_FILTER_CAN_IDS or something to use in both the can_id_list_size and the loop.

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@rureverek rureverek May 4, 2023 •
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Are you sure this should be NUM_FILTERS * NUM_IDS_PER_FILTER? This would be 28*4=112 which is bigger than size of hashmap. The i is used only for hashmap entries, not counting can_ids. Instead, I can put break statement in case number ids will be bigger than NUM_FILTERS * NUM_IDS_PER_FILTER.

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My mistake, you're absolutely right. Honestly no idea what I was thinking sorry!

{
if(rtcan_h->subscriber_map[i] != NULL)
{
/* CAN ID found! */
can_id_list[number_ids] = rtcan_h->subscriber_map[i]->can_id;
number_ids++;

}
}

int number_banks = (number_ids-1)/4 + 1;

/* Error if there's too many ids to apply filter */
ADD_ERROR_IF(number_banks > 28, RTCAN_ERROR_INIT, rtcan_h);
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if (no_errors(rtcan_h))
{
CAN_FilterTypeDef filter;
filter.FilterActivation = ENABLE;
filter.FilterFIFOAssignment = CAN_FILTER_FIFO0;
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Do we know what this FIFO assignment does? I don't know if we ever want to use anything other than FIFO0, but maybe its important?

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According to datasheet: "If there is a match, the message is stored in the associated FIFO". Basically, when there's filter match, the data can be saved either in FIFO0 or FIFO1. Actually, this one may be useful for prioritizing certain IDs over another IDs which are in the same CAN bus.

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From slides on the F7 bxCAN peripheral:

"Two receive FIFOs are used by hardware to store incoming messages. Each FIFO can store three complete messages."

So I don't think there's any inherent prioritisation of one FIFO over another, unless we did this as a feature of RTCAN where it will read and distribute the messages from one FIFO first, but I don't think we need that level of prioritisation.

I think we might want to consider using both FIFOs to share the load (so we use all 6 available message slots rather than just the 3 in FIFO0). Maybe having it alternate between FIFOs each loop?

filter.FilterMode = CAN_FILTERMODE_IDLIST;
filter.FilterScale = CAN_FILTERSCALE_16BIT;

/* Configure Filter IDs for each filter */
for(int i = 0; i < number_banks; i++)
{
filter.FilterIdHigh = can_id_list[4 * i] << 5U;
filter.FilterIdLow = can_id_list[4 * i + 1] << 5U;
filter.FilterMaskIdHigh = can_id_list[4 * i + 2] << 5U;
filter.FilterMaskIdLow = can_id_list[4 * i + 3] << 5U;
filter.FilterBank = i;


HAL_StatusTypeDef hal_status = HAL_CAN_ConfigFilter(rtcan_h->hcan,
&filter);

ADD_ERROR_IF(hal_status != HAL_OK, RTCAN_ERROR_INIT, rtcan_h);
}
}


TX_THREAD* threads[2] = {&rtcan_h->tx_thread, &rtcan_h->rx_thread};

for (uint32_t i = 0; i < 2; i++)
Expand Down