ANT Forum

In the ANT message protocol and usage PDF, it says that setting Transmission Type to 3 (section 8.2) is used for 2 byte shared address. Is this just for SensrCore scripts, or is there a value that will allow only 1 byte for the shared address, and thus, a 7 byte payload?

For example, if I set the Transmission Type to 2 (guessing this means 1 byte address if 1 is no shared address (section 8.1) and 3 is 2 bytes? (section 8.2)), and Channel Type to 0x30 on the master, Transmission type to 2, Channel type to 0x20 on the slaves, do I get a 7 byte payload and 1 byte shared address?

Josh      

Hi Josh,

Newer ANT modules (i.e. AP2, C7) support variable size shared address, so using a Transmission Type of 2 when configuring a shared channel slave with these modules will allow for a 1 byte shared address, and a 7 byte data payload. However, older modules (i.e. AT3) do not support variable size shared address, and setting the transmission type to 2 does the same thing as setting the transmission type to 3, allowing for a 2 byte shared address and a 6 byte data payload.      

So is setting Transmission Type required for shared channel operation? We are using AP2 modules.

If so, are the only relevant settings:

1 = no shared address
2 = 1 byte shared address
3 = 2 byte shared address

What do other numbers do? Is this required for both master and slave?      

In shared channel configuration, only the last two bits of the transmission type are taken into account. In other words a transmission type of 6 is the same as a transmission type of 2, and a transmission type of 15 is the same as a transmission type of 3 etc. This means only values from 0 to 3 are used to determine the length of the shared address.

0, 1, and 3 indicate a 2 byte shared address
2 indicates a 1 byte shared address (In newer modules only)

If you require a 1 byte shared address and a 7 byte data payload, then it is necessary to set the transmission type to 2, or any other corresponding value for the AP2 module.

However, if you were using the AT3 module, setting the transmission type is irrelevant, as any number for transmission type corresponds to a 2 byte shared address.

Thank you for this question, it has brought a few inconsistencies in the documentation to light. I will fix them as soon as possible.      

And to answer the last part of your question, 'Is this required for both master and slave?', the slave's transmission type must either be set to zero (wildcard) so it can search for any available master that is transmitting, or to the same as the master. Setting it to anything else will result in no data received.      

Thanks, that clears it up a lot.

Josh