TopObject memory and FDS StartUp question.

CannibalRobotics

How does one determine the 'stack' usage of the top object?
With other objects, there is a stack address and size that can be used.

If I want to start and stop FullDuplex serial to change the i/o pin numbers to communicate with multiple devices, how long should I wait to send data after calling the start. I'm thinking in SPIN terms it's pretty quick since it's a PASM object.

Thanks in advance-

StefanL38

If I remember right starting a new cog takes around 100 microseconds. You could try to immediatly send a string after the serial.start-command. If the string has different chracaters it will be easy to see which characters are readedin properly on the receiverside.
Anyway FullDuplexSerial uses a sendbuffer. This means if you want to send characters they get stored in the buffer. This storing is done by the SPIN-cog who calls the methods str, dec, bin etc. As long as you don't "overfill" the sendbuffer I guess you can start immediatly.

keep the questions coming
best regards

Stefan

Dave Hein

Jim,

When you say "TopObject" I think you really mean "cog 0". Each Spin cog requires it's own stack. The first cog that starts up will use the memory immediately after the VAR space for it's stack. This stack could extend all the way to the end of hub RAM, though most programs use less than 100 longs for their stack. In your other thread about Stack Posers I posted some code that measures cog zero's stack usage.

pub WritePattern
  longfill(@result + 40, $F00DFEED, ($8000 - @result - 40) >> 2)

pub StackUsed | ptr
  ptr := $7FFC
  repeat while long[ptr] == $F00DFEED
    ptr -= 4
  return ptr + 4 - WORD[10]

WritePattern put's a known pattern in cog zero's stack area. StackUsed will return the number of bytes that have been used. WritePattern must be called from cog 0, but StackUsed could be called from another cog, which could continually montor cog zero's stack.

As far as FDS. You can write to it immediately after you call the start routine. The data will queue up in the outbound buffer, and TX will wait if the buffer gets full.

Dave

Mike Green

Your problem isn't so much in waiting after starting FDS before sending the first character, it's the question of when FDS is finished sending what's already in the buffer and then waiting for it to actually finish sending the last character so you can stop FDS and change to a different set of I/O pins. To do this, you have to add an additional routine to see when the transmit buffer is empty, then wait an amount of time equal to at least 10 bit times for the last character to be sent. I think there's a txcheck in the FDS routine used in DongleBasic (from the Object Exchange) that does what you want. You might have a look at that. I don't have access to any of my objects at this time.

kuroneko

In addition to what Mike said, have a look at the thread [thread=129809]FullDuplexSerial Object - Detecting when data has been sent[/thread] for previous discussions (and solutions).