Telegraf config file - substrings and converting hexadecimal to int for ingestion - influxdb

Question

I have incoming BLE beacon data from a gateway in the following format:
{"msg":"advData","gmac":"94A408B02508","obj":
[
{"type":32,"dmac":"AC233FE0784F","data1":"0201060303F1FF1716E2C56DB5DFFB48D2B060D0F5A71096E000000000C564","rssi":-45,"time":"2022-10-13 02:46:24"},
{"type":32,"dmac":"AC233FE078A1","data1":"0201060303F1FF1716E2C56DB5DFFB48D2B060D0F5A71096E000000000C564","rssi":-42,"time":"2022-10-13 02:46:26"}
]
}
and I want to extract the attributes gmac, dmac, rssi, and process attribute data1 and ingest these into influxdb via a telegraf config file.
I can successfully ingest gmac, dmac, and rssi using the below telegraf config:
## Data format to consume.
## Each data format has its own unique set of configuration options, read
## more about them here:
## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
data_format = "json_v2"
tagexclude = ["topic"]
[[inputs.mqtt_consumer.json_v2]]
measurement_name = "a"
timestamp_path = "obj.#.time"
timestamp_format = "unix"
[[inputs.mqtt_consumer.json_v2.tag]]
path = "gmac"
rename = "g"
[[inputs.mqtt_consumer.json_v2.tag]]
path = "obj.#.dmac"
rename = "d"
[[inputs.mqtt_consumer.json_v2.field]]
path = "obj.#.rssi"
type = "int"
rename = "r"
However, I'm not sure how to process the data1 attribute where I need to (1) extract characters 15 and 16 and convert this from a hexadecimal value to an integer, and (2) extract characters 13 and 14 and convert each hexadecimal value to an integer before combining them together as a float (character 13 is the whole number component, character 14 is the decimal component).
Can anybody provide some guidance here?
Many thanks!

Answer 1

Got it working thanks to some help over at Influx Community, I've pasted the relevant section of the telegraf config file if this is of help to anyone else:
data_format = "json_v2"
tagexclude = ["topic"]
[[inputs.mqtt_consumer.json_v2]]
measurement_name = "a"
timestamp_path = "obj.#.time"
timestamp_format = "unix"
[[inputs.mqtt_consumer.json_v2.tag]]
path = "gmac"
# g is gateway MAC address
rename = "g"
[[inputs.mqtt_consumer.json_v2.tag]]
path = "obj.#.dmac"
# d is beacon MAC address
rename = "d"
[[inputs.mqtt_consumer.json_v2.field]]
path = "obj.#.rssi"
type = "int"
# r is RSSI of beacon
rename = "r"
[[inputs.mqtt_consumer.json_v2.field]]
path = "obj.#.data1"
data_type = "string"
[[processors.starlark]]
namepass = ["a"]
source = '''
def apply(metric):
data1 = metric.fields.pop("data1")
tempWhole = int("0x" + data1[26:28], 0)
tempDecimal = int("0x" + data1[28:30], 0)
tempDecimal = tempDecimal / 100
# t is temperature of chip to two decimal points precision
metric.fields["t"] = tempWhole + tempDecimal
# b is battery level in mV
metric.fields["b"] = int("0x" + data1[30:34], 0)
return metric
'''