A computer can also communicate directly with the EVM over USB. The EVM is programmed to accept a few commands so that register access can be achieved. The main two commands are to read a register using "rreg" or to write a register using "wreg". The register read takes the desired register address as an argument and returns a confirmation with the register address number, value of the register in decimal, and the state of the EVM. A register write takes the address and value of the register as two separate inputs in hexadecimal format. The write command then returns and acknowledgment along with the EVM state following the command. Even though the arguments are required to be in hexadecimal format, there are a few different options for them. They can either include a prefix of "0x" or not as long as the "x" is always lower case. Here is an example of the different ways to read register address 0x04:

• rreg 4

• rreg 04

• rreg 0x04

An example of a register read for the STATUS register (address 0x00) would be to send the command "rreg 00". The confirmation received from this command will show as follows:

{"acknowledge":"rreg 00"}

{"register":{"address":0,"value":64}}

{"evm_state":"idle"}

An example of a register write command would be to send "wreg 0A 01". This writes the value 0x01 to the RESET register of the device. The confirmation received for this command can be seen below:

{"acknowledge":"wreg 0A 01"}

{"console":"Writing 0x0001 to RESET register"}

{"evm_state":"idle"}

This same syntax can be used for complete register access to the device. An important thing to note is that the data registers (addresses 0x02 through 0x08 for button algorithm and 0x59 through 0x64 for raw data) have been combined in the command so that only the first of each channels data needs to be used to get the data. For example, to get the raw data from channel 0, the command "rreg 59" will grab all three data registers and combine them properly before returning the value in decimal format.