GARMIN GPS Interface Specification

6. Application Protocols
6.1. A000 – Product Data Protocol
All GPS products are required to implement the Product Data Protocol using the default physical and basic link
protocols described earlier in this document (i.e., the default RS-232 settings and the default packet format). The
Product Data Protocol is used to query the GPS to find out its Product ID, which is then used by the Host to
determine which data transfer protocols are supported by the connected GPS (see Section 1.1, , on page 61).
The packet sequence for the Product Data Protocol is shown below:
N Direction Packet ID Packet Data Type
0 Host → GPS Pid_Product_Rqst ignored
1 Host ← GPS Pid_Product_Data Product_Data_Type
Packet 0 (Pid_Product_Rqst) is a special product request packet that is sent to the GPS. Packet 1
(Pid_Product_Data) is returned to the Host and contains data to identify the GPS, which is provided in the data type
Product_Data_Type.
6.1.1. Product_Data_Type
The Product_Data_Type contains two 16-bit integers followed by one or more null-terminated strings. The first
integer indicates the Product ID, and the second integer indicates the software version number multiplied by 100
(e.g., version 3.11 will be indicated by 311 decimal). Following these integers, there will be one or more nullterminated
strings. The first string provides a textual description of the GPS product and its software version; this
string is intended to be displayed by the Host to the user in an “about” dialog box. The Host should ignore all
subsequent strings; they are used during manufacturing to identify other properties of the product and are not
formatted for display to the end user.
The type definition for the Product_Data_Type is shown below:
typedef struct
{
int
product_ID;
int
software_version;
/* char product_description[]; null-terminated string */
/* ... zero or more additional null-terminated strings */
} Product_Data_Type;
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