XBees are talking for real

Turns out what was missing was a resistor between the bus pirate and the receiving line on one XBee. Then it was a resistor between the other XBee and the receiving line for the ACV Pic. Either way, with all of our 1Ks in place, we have communication!

Oh, and blinky lights. The E128 has enough ports that I can control all the lines on 5 RGB LEDs (for display atoll possession status) and still have room left over for accelerometer and potentiometer inputs, a whole bunch of other switches, maybe some debugging lines, etc. Good stuff.

Things for me to do by the end of the week:

• I know transmitting is working on the CVC, now I need to be able to receive.
• Get it reading sensor data and composing messages accordingly.
• Start parsing messages from the ACV, other players, and wherever messages will come from.
• On that note, read the communications protocol carefully and understand everything I'll have to handle.
• Package everything nicely into state machine format.
• Start soldering the final versions of circuits as they finish.

Communication charts, state diagrams, things to do ...the usual

Will's website

http://me218c.weebly.com/

Updates From Friday (May 6, 2001)

Today: 6 May
parts yet to receive: propeller

coding done:
ACV:tested PWM and motors
tested RFID, works completely.
written Security chip State Machine
written Receive part of State Machine on Main PIC

CVC:
written State Machine. Currently Testing

Xbee:
testing. don't yet know if they work

To do:
start soldering bigger circuits (if any)
start prototyping (after Matt's exam)

Things to buy/get:
larger circuit board, wires?
a box to keep all our material in place

Small Snippets of Code that may be required to check the Receive State Machines:
A code which sends a fixed formatted message from e128
a code which sends a fixed formatted message from the pic

Aims for next couple of days:
protoyping after Matt's exam finishes tomorrow
get Xbee working (hopefully tonite)
Get ACV and CVC state machines working (hopefully by tmrw nite)
We have to get this done by Monday, 9 May. 10 May is the checkpt.

Attached is an almost final draft of the protocol decided by the Comm Comm.

Trying to Get the XBee to Talk

Things to take note of:

• Length and checksum are referring to just the data (after the start byte and length, before the checksum).
• If the lights aren't on, the XBee isn't working.
• Bus pirates are awesome.

Hopefully good progress will be made today. It appears my skeleton state machine for the E128 on the CVC is functional. Now I just have to get more than garbage back from the XBee.

Also, the PIC16F777 arrived this morning. It looks like a beast.
 $11.62 from Microchip Direct.

Comm-Comm Notes

Requests to capture an atoll are broadcast messages which only specify the serial number of the atoll, and not the address of the atoll's radio.

We can set an option byte to receive all broadcast messages. A broadcast message is any message which is directed to address 0xFFFF.

Pre-built messages will work well with a test harness.

What to do with transmit status? Only applicable to directed messages.

What does the transmit message look like?

Add cycle limiter or timeout limit for any message transmission.

Draft will be completed by Friday, Final Draft due next Tuesday.

Motors + Drivers

We decided to use a pair of beefy Johnson Automation motors from Jameco. Its operating range is 13.5V and 1.44A, and it spins at 18500 rpm.

We will be pairing this with a LMD18200 H-bridge, http://www.national.com/ds/LM/LMD18200.pdf