Generic Master

Master Command Group

With the Master Commands, the interface can be used to implement or simulate a "Vending Machine Controller".

Any communication initiated with the following commands will send out on the "TX" line of the MDB interface, answers will be expected on the "RX" line.

The M command is used to start or stop Master Mode. On the Pi Hat interface starting Master Mode will automatically set the slave (RX) interface pull-up to active so that slaves can answer to the master.

Stopping Master Mode will disable the pull-up on the RX interface line.

M,1 #start master mode (and set the slave line pull-up)

M,0 #stop master mode (and disable the slave line pull-up)

Possible answers from the interface:

m,ACK #success on enable/disable master mode m,NACK #unknown parameter on master control

Request Command Group (used for Master implementation)

MDB Generic Master sends request to the Bus using "R" command set. These commands have the following structure.

R,xx,yyyy #send a command/request to slave xx with data yyyy

Info

The xx and yyyy data has to be checked directly on the MDB protocol here

Possible answers from the interface:

Info

These answers are actually sent by the slave (either simulated with the MDB interface or sent by an actual peripheral like a coin acceptor or a cashless device).

p,ACK #the slave device sent an ACK to the command (it received and acknowledged the command) p,NACK #the slave device did not answer to the command (maybe there is no slave with address xx) p,YYYY #the slave device answered with the YYYY command

Example

R,14,01 - send "reader enable" command to cashless device on address 0x10

- note that the arguments are given in hexadecimal, 2 digits

R,RESET #issue a bus reset condition to the MDB Bus

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