Just enter the serial number in the serial number box?

ANT+ serial number are not always clear-cut. It is sometimes difficult with ANT+ to find the “real” serial number as, often, on the box or device, the manufacturers mix it up with text and perhaps more numbers and product codes. When you search with a central device with a display (such as a bike computer or, ideally, a PC) it can display all information it has and it is easy to say "that's the one" as firstly a human is reading the information and there is likely only one device present at the time. The Pilot however must be able to make an exact match.

Let's say the box says the serial is ZPH100001234567. A PC can interrogate the ANT device which will report its serial number and manufacturer IDs to the PC. The PC has the luxury of an internet connection (or stored database) and can resolve the received manufacture ID into human-readable text. So a PC might be able to say:

Connect to Zephyr 123456?

It is clear that your device ZPH100001234567 is what the PC is calling Zephyr 123456 so all is well. If this is the case then what you need to tell the Pilot for serial number is simply "123456".

So that much was easy. However, there are a number of ways confusion arises and it has to do with the way numbers are stored and transmitted (see Binary, Decimal and Hexadecimal). ANT actually searches for devices using only the lower 16bits of the serial and uses a tucked away extra 4bits to extend the total available serial numbers for a manufacturer to 20bits.

So what do these look like compared to what you enter? On the left of the table is what you may (optimistically) enter into Embedded Setup. What computers deal in though is hex so that is what, in the second column, we show the exact same number written as.

 You enter  Your number in hex 20bits 20 bit decimal 16bits 16bit decimal
 123456  0x1E240  0x1E240 123456  0xE240 57920
 1234567  0x12D687  0x2D687 185991  0xD687 54919
 10000123456  0x2540DC640  0xDC640 902720  0xC640 50752
 100001234567  0x174889BE87  0x9BE87 638599  0xBE87 48775


What you should enter is: 123456 (which is 0x1E240).

However, behind the scenes, one extra caveat remains. ANT device serial numbers are found using 16bits plus a further 4bits hidden in another value. This can make inspection very confusion.

In the above example, the decimal serial number 123456 is represented as 0x1E240 in hex. Which is 17bits long. The number looked for in the ANT packet would only be 16 bits - which is 0xE420 - which in decimal becomes the impossible to recognise 57920!