A message to the gateway begins with a 4 character tag. In case the SAPI tag is used, the gateway will return a message according to the SPBus Protocol. However, older gateway versions do not support this method, and return an array representing either an array of data, or one bytes as an error code. For these versions, the SPGW tag is used. In the code and documentation, SAPI is referred to as Extended mode, and SPGW as Simple Mode.
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A message to the gateway begins with a 4 character tag. In case the SAPI tag is used, the gateway will return a message according to the SPBus Protocol. However, older gateway versions do not support this method, and return an array representing either an array of data, or one bytes as an error code. For these versions, the SPGW tag is used. In the code and documentation, SAPI is referred to as Extended mode, and SPGW as Simple Mode.