Learn the main parameters you need to look for when dealing with RFID reader APIs and programming for UHF RFID solutions including battery-free sensors.
You now know that optimizing RFID reader software will depend a lot on the APIs you have available to program your solution.
‘What should I look for?’
Remember that we are talking about optimizing software for RFID sensor tags. If you are interested in identification tags only you are probably better off using the manufacturer’s software.
When working with sensor tags you will have to balance between increasing read range – transmitting more power – and having a higher data rate – communicating faster.
Let’s start with the straight-forward items. You will improve read range, data rate or both of them with these:
- Maximum output power: Obviously, the higher the output power, the longer the communication range of the system.
- Idle time between commands: APIs generally set an idle time between commands, limiting you the possibility to send more commands even there would be time for them.
Sending more commands means both more power transmitted and the possibility to communicate faster so reducing this idle time is key.
- Access to libraries: This one is not about improving the system but just about being able to program at all! You need to make sure the APIs are available for the OS you want to develop under. It is not obvious that a manufacturer will have the APIs for Android or iOS for example – not even for Linux.
These are more complex to deal with as changing them will optimize the system in one direction but will make it work worse in the other. The most important to look for are:
Q. This parameter is defined by the standard to make sure there are no collisions between communications of different RFID tags in the system. In general, for low volumes of tags a low Q is
recommended which makes the system faster. For high volumes you will need a higher Q, which also grants you a better duty cycle – more power transmitted.
The key with the Q parameter is understanding if, at all, you want to use a higher Q when you don’t really need it. Even if the system may slow down in showing you the identification numbers, the capacitor will charge faster.
Coding. The standard defines up to four different coding options – FM0, Miller2, Miller4 and Miller8 from faster to slower. The idea is that faster coding (FM0) can read faster and slower coding takes longer because it ‘repeats’ data, making it more difficult for the tag to not understand each message.
The key with the coding is understanding that slower coding transmits more power – takes longer to send so duty cycle is higher. You can always move to faster coding as long as:
- The RFID tag has no problem in understanding the signaling.
- The RFID tag has enough energy to power up the sensor.
Testing multiple configurations – a must
There are of course many more parameters such as Tari, RTcal or TRcal. Even though these do not impact the results as much as the ones mentioned above, you should always test multiple
configurations to take your own decisions on what to implement for your specific solution.
For more information about read range in RFID systems download the ‘The essential guide to developing RFID sensor software‘ free eBook.