Specifications

ManualsBrandsDigi-Frame ManualsComputer equipmentA4 Multi-Purpose

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8.APIOperation

API (Application Programming Interface) Operations are available for communicating with an

external processor through its UART port. API operation requires that communication with the

module be done through a structured interface (data is communicated in frames in a defined

order). The API specifies how commands, command responses and module status messages are

sent and received from the module using a UART Data Frame.

Please note that Digi may add new API frames to future versions of firmware, so please build into

your software interface the ability to filter out additional API frames with unknown Frame Types.

API Frame Specifications

Two API modes are supported and both can be enabled using the AP (API Enable) command. Use

the following AP parameter values to configure the module to operate in a particular mode:

•AP = 1: API Operation

•AP = 2: API Operation (with escaped characters)

API Operation (AP parameter = 1)

When this API mode is enabled (AP = 1), the UART data frame structure is defined as follows:

UARTDataFrameStructure:

MSB=MostSignificantByte,LSB=LeastSignificantByte

Any data received prior to the start delimiter is silently discarded. If the frame is not received

correctly or if the checksum fails, the module will reply with a module status frame indicating the

nature of the failure.

API Operation - with Escape Characters (AP parameter = 2)

When this API mode is enabled (AP = 2), the UART data frame structure is defined as follows:

UARTDataFrameStructure‐withescapecontrolcharacters:

MSB=MostSignificantByte,LSB=LeastSignificantByte

Escape characters. When sending or receiving a UART data frame, specific data values must be

escaped (flagged) so they do not interfere with the data frame sequencing. To escape an

interfering data byte, insert 0x7D and follow it with the byte to be escaped XOR’d with 0x20.

Length

(Bytes 2-3)

Checksum

(Byte n + 1)

MSB LSB 1 Byte

Start Delimiter

(Byte 1)

0x7E

Frame Data

(Bytes 4-n)

API-specific Structure