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The serial UART interface uses the following parameters:
Table 1: RapidHA Serial Parameters
| Parameter | Value |
|---|---|
| Baud Rate | 115200 |
| Parity | None |
| Stop Bits | 1 |
| Data Bits | 8 |
Frame Structure
Every RapidHA frame has the structure illustrated below:
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Table 2: Frame Header Description
| Byte | Field Name | Description |
|---|---|---|
| 0 | Start of Frame | Fixed value of 0xF1; will be referred to as START_OF_FRAME throughout this document. |
| 1 | Primary Header | Defines the primary frame type. |
| 2 | Secondary Header | Identifies the command subset of the given primary frame type. |
| 3 | Frame Sequence Number | 0 – 127: Host initiated transactions 128 – 255: Module initiated transactions |
The Frame Sequence Number enumerates a serial message exchanged between the Host and the Module, and vice versa. Use of a Frame Sequence Number for each such message is recommended. For best practice, we also recommend the Frame Sequence Number be incremented by 1 for each newly initiated |
message |
. Any transaction, whether initiated by the Host or the Module, may be acknowledged (i.e., ACK'ed) by the recipient with a response using the same Frame Sequence Number. The Frame Sequence Number is used for tracking purposes but is not a mandatory feature. If its use is not desired, it should be assigned a value of 0x00. | ||
| 4 | Payload Length | Defines the length of the payload of a received or transmitted frame as 0-n bytes; at the time of this writing, the maximum acceptable values for n are:
Received by Module – 0x7A or 122 bytes |
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Payload
Unlike the header, the payload is of variable size, ranging from 0 to n bytes; the size is based on the Payload Length field in the header. All fields contained in the payload are ordered with the least significant byte first.
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