support ether:begin to work with mac placed in flash

[nagimov]

This is a replacement to PR #397 supporting EtherCard:begin to work with mac-addresses placed in flash via PROGMEM.
Since the signature of existing EtherCard:begin implementation expects mac as const uint8_t* macaddr and captures PROGMEM arrays, I think it is easier to supply an extra bool rather than reimplement it with const __FlashStringHelper*.

EtherCard/src/EtherCard.h

Lines 130 to 131 in 420dd84

	static uint8_t begin (const uint16_t size, const uint8_t* macaddr,
	uint8_t csPin = SS);

I surely could be missing an obvious better way to do this.

Tested on nano v3 with old bootloader.

[nuno-silva]

Having an optional argument telling whether to read from RAM is a lot more error prone than overloading the method to properly handle it automatically.
That being said, I think this optional bool argument approach is used somewhere else in the code too.

These are my two cents

[nuno-silva]

update docs here

[nuno-silva]

remove debug print

[nuno-silva]

Also, if you're defaulting to macFromRam=false, this means that most of the examples (e.g. etherNode, nanether, ...) will need to be updated accordingly. Hence another reason why overloading would be better.

[nagimov]

@nuno-silva
I agree that "smarter" EtherCard:begin() is a better approach. I'm not confident enough in my cpp to do such a rewrite though :) I'm happy to test a better version if someone could do the rewrite, I have Uno and Nano v3.
I went with optional bool since dhcpSetup and dnsLookup also use it:

EtherCard/src/EtherCard.h

Line 359 in 420dd84

static bool dhcpSetup (const char *hname = NULL, bool fromRam =false);

EtherCard/src/EtherCard.h

Line 380 in 420dd84

static bool dnsLookup (const char* name, bool fromRam =false);

You're right regarding examples - many of them place mymac into SRAM apparently:

$ find ./examples -type f -exec grep -l "static byte mymac\[\] = " {} \;
./examples/testDHCPOptions/testDHCPOptions.ino
./examples/backSoon/backSoon.ino
./examples/pings/pings.ino
./examples/persistence/persistence.ino
./examples/xively/xively.ino
./examples/multipacketSD/multipacketSD.ino
./examples/webClient/webClient.ino
./examples/getDHCPandDNS/getDHCPandDNS.ino
./examples/udpClientSendOnly/udpClientSendOnly.ino
./examples/multipacket/multipacket.ino
./examples/testDHCP/testDHCP.ino
./examples/rbbb_server/rbbb_server.ino
./examples/thingspeak/thingspeak.ino
./examples/udpListener/udpListener.ino
./examples/SSDP/SSDP.ino
./examples/JeeUdp/JeeUdp.ino
./examples/noipClient/noipClient.ino
./examples/etherNode/etherNode.ino
./examples/getStaticIP/getStaticIP.ino
./examples/getViaDNS/getViaDNS.ino
./examples/notifyMyAndroid/notifyMyAndroid.ino

I'll add another commit updating all the examples. However seeing how many of them (and potentially existing code) are going to get affected, I'm not sure anymore whether this PR should be merged 👎

[nuno-silva]

@nagimov tell you what: I'll implement it as I suggested when I get a chance (maybe tomorrow) and then you can test it for me :)

[nagimov]

fixed by #406