![]() ![]() This means you’re now making a serial connection with the XBee explorer board connected to your computer rather than directly to your Arduino so when the connection is made, the Arduino board will not be reset automatically and the startup sequence will not run. Now the issue with using an XBee wireless link is that your Arduino board is no longer connected to your computer (and well, that’s the whole point of using XBees in this way). Once you receive the final END_SYSEX (0xF7) byte you know that Firmata is in the “ready” state. What many Firmata client implementation do to ensure the board is “ready” is to listen for the initial Firmata version and firmware messages. During the blink version sequence the UART is capable of receiving serial data in the background, but the processor will not be able to send a response until after the sequence has ended so consider this unreliable. ![]() ![]() What is important to note here is that during this startup sequence you cannot reliably send any Firmata commands to the Arduino board. So you make a serial connection, the Arduino board is automatically reset and the startup blink sequence occurs. If it executes the entire blink version sequence, then the serial connection is automatically resetting your board. You can also just create a serial connection from your Firmata client and look at the onboard (pin 13) LED. See this link to determine whether or not your Arduino board is using auto-reset (it most likely is). This is standard among all newer Arduino boards that support automatic reset when loading a sketch (in the earlier days of Arduino you had to physically press the reset button on the board prior to uploading a new sketch… the DTR hack automates this). This is because the DTR (Data Terminal Ready) pin is wired to reset the Arduino and the DTR pin is toggled when a serial connection is made (hence the data terminal is now ready). The most important of them is to understand that when you make a new serial connection from a Firmata client application your Arduino board is reset. There are several things to be aware of here. What does this have to do with using XBees? First a REPORT_VERSION message is sent (assuming Frimata v 2.3) then immediately after a REPORT_FIRMWARE message is sent. The entire Firmata blink version sequence takes a little over 1.6 seconds to execute and this does not include the time of the general Arduino startup blink sequence.Īfter the startup blink sequence completes, 2 Firmata messages are sent (this is the blink sequence you see on the TX line immediately following the pin 13 blink sequence). The final sequence blinks indicate the Firmata minor version (either 2 or 3 depending on the version of StandardFirmata you have loaded). So that first blink doesn’t mean anything. The following 2 blinks indicate the Firmata major version (2 in this case). The first blink of this sequence occurs because the Arduino starts up with all digital pins initialized to INPUT (this causes the blink LED to illuminate, then StandardFrimata starts and initializes all digital pins to OUTPUT which turns the blink LED off. The following set of 3 blinks begins when Firmata.begin(57600) is called within StandardFirmata (or any other Firmata sketch for that matter). You’ll see this with any Arduino sketch you run. This happens before StandardFirmata even runs. The initial set of blinks is the Arduino starting up. You will then see the TX led blink rapidly. If you load StandardFirmata onto an Arduino board and look at the on-board blink LED (connected to pin 13 on many boards) when you reset the board, you’ll see this LED blink rapidly, then after a brief pause you’ll see it blink 3 times followed by a short pause and then it will blink 2 or 3 more times (depending on which version of StandardFirmata you have loaded). Firmata Startup Sequenceīefore we get into XBee configuration, it’s important to understand the Firmata startup sequence and whether or not your Firmata client relies on certain messages sent during the startup sequence. But first it helps to have an understanding of the Firmata startup sequence. I’ve been using XBees with a couple of different Firmata client libraries ( and BreakoutJS) for few years so I figured I’d share my knowledge of configuring XBees and the issues presented by using XBees in Firmata-based applications. There are obvious advantages here if you making anything that moves, flies or would otherwise be constrained by a physical serial link. You’d have a second XBee connected to your Arduino board (we’ll refer to this node as the “end point”). In such a setup you’d have a single XBee radio connected to a computer running the Firmata client application (we’ll refer to this XBee node as the “coordinator”). There seems to be a fair amount of interest lately in using XBee to create wireless Firmata client applications.
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