1. A payment reader for processing transactions with a payment device, comprising: a payment interface configured to interface with the payment device and to receive payment information from the payment device; a memory comprising a plurality of firmware modules, the plurality of firmware modules comprising a message dispatcher module and a plurality of functional modules, the plurality of functional modules comprising a payment module associated with the payment interface and a transaction processing module associated with processing of the payment information; and a processor coupled to the memory to execute instructions in the plurality of firmware modules to execute instructions associated with the plurality of functional modules based on one or more messages provided by the message dispatcher module, receive payment information based on the payment module and a first message of the one or more messages, and process the payment information based on the transaction processing module and a second message of the one or more messages, the first message associated with a first message type of the one or more messages that is associated with the concurrent operation of the functional modules and the second message associated with a second message type of the one or more messages that is associated with an ordered processing of the functional modules.