DynamoBen
- 1st June 2005, 14:55
I have a door entry device that reads magnetic cards and then allows access based on card number. Currently there is an onboard EEProm database with valid card numbers programmed into it. In addition this device can connect to an RS-485 network an communicate back to a central computer. I've opted to go the master and slave route to simplify communications. However, I'm hung up on how to solve one problem.
When a card is swiped, I want to report that card number back to the central computer via the network. Since I'm polling each slave I'm afraid that I may "miss" a swipe from time to time. (if another swipe occurs prior to when I poll the slave) Should I be storing these swipes into a buffer variable and then send them when the master polls? How big should the buffer be, should I store multiple swipes in this buffer?
Or am I being paranoid, store just one and be done with it?
Thoughts?
When a card is swiped, I want to report that card number back to the central computer via the network. Since I'm polling each slave I'm afraid that I may "miss" a swipe from time to time. (if another swipe occurs prior to when I poll the slave) Should I be storing these swipes into a buffer variable and then send them when the master polls? How big should the buffer be, should I store multiple swipes in this buffer?
Or am I being paranoid, store just one and be done with it?
Thoughts?