Stamp to Stamp

Nick Waldvogel

Good Morning Everyone

I have been doing some checking on this and seem to have gotten mixed feelings about the best way to hook two stamps together. I basically want one stamp to send its info to the other stamp and then the 2nd stamp can send the info on to where it needs to be sent. What is your opinion on the best way to accomplish this?

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I'm just 10 people short of a threesome!!

Mike Green

There are examples in the Nuts and Volts articles on making a "mini-network" with two or more Stamps. For example, you can use one pin from each Stamp that you connect between the Stamps with a pull-up resistor of 4.7K to 10K to +5V. One Stamp signals the other by setting the pin to LOW for a brief time. When the other Stamp notices that, it waits for the pin to go to HIGH. The first Stamp sets the pin to INPUT and waits for data using SERIN. If nothing is received, the first Stamp tries signalling again. Essentially, the first Stamp has signalled the second one that it's ready to talk and sees if there's a response. The response is some agreed upon message so that the two programs are in synchronization.

PJAllen

There is also an example in PBASIC Help (see SERIN/SEROUT), wiring and all.

allanlane5

Yup, SEROUT/SERIN is the best way. Then, the question is, how do you physically connect them? Answer -- plain wire if they're within 10 feet of each other, put in a MAX232 RS232 driver circuit for 50 feet to 150 feet. And you MUST put a ground wire in, to link the signal ground of both boards.

If they're on the same board, you already have a common ground, of course.

crgwbr

I've been wanting to do the same thing for a while, never got around to it. Anyway, you say serin/serout is the way to go, can I conect the stamps via there DB9 port, if so strait through cable or null modem cable.

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NerdMaster
For
Life

allanlane5

Hmm. The BS2 DB-9 connector uses a couple of on-BS2 transistors to modulate the incoming TX 12-volt signal to make the RX signal back to the PC. Thus you probably wouldn't want to connect two BOE board's that way, there wouldn't be a source of 12 volts. Plus you couldn't then use the PC to monitor the BS2's.

However, you can wire your own DB-9s -- pin 2(TX), pin 3(RX), and pin 5 (Vss). Then connect the boards that way. And since you have control of which pin of the BS2 talks to which pin of the cable, you can use either a null-modem or straight-through.