Re: [lwip-users] Help with LwIP Modem

[Jaime Fernandez Hoffiz]

Hi All,

To close the loop on my original question maybe it can help another rookie like me.

My goal was to set my ethernet device so that it will act as a cable, received packets from the netif, modulates them, send them over a cable, have another device demod, the exact same packet, and last transmit the packet out over its netif.

My initialization changed from:

// netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_IGMP;

netif->flags = 0;

Now I'm able to receive all incoming packets but not answer or react to any of them. For example, if I ping the target I see the packet but lwip does not ack and replies back.

Thanks all for the help and suggestions.

Jaime

On Sat, Jul 9, 2016 at 3:30 PM, Jeff Barlow <address@hidden> wrote:

On 07/09/2016 12:10 PM, address@hidden wrote:

Jeff Barlow wrote:

I think you will find that ChibiOS does much the same. The reasoning
as I understand it is to keep ISR code paths as short as possible to
minimize latency in hard real time systems.

Without knowing ChibiOS in detail, I'd be interested in knowing what
would be the actual penalty of removing the need for the API user to
supply the "bool inIsr"...

I don't claim to be an expert on ChibiOS in particular. It seems fairly obvious to me though that inserting extra code in the ISR path that inspect some globals only to figure out that it is indeed in an ISR will have an adverse effect on latency. ChibiOS is very tightly tuned to minimize latency. For some of us this makes the difference between a working system and one that almost works.

--
Later,
Jeff

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