Modbus mode never returned a reading: every status poll came back as "the
charger did not answer", though the charger was answering all along. It was
refusing the question. The A5191 splits its map across two tables where the
spec's single 2xxxx column suggests one — 20000-20100 are input registers and
reject FC03 with an illegal-address exception at every address in the range,
while 21000-21005 really are holding registers and read back over FC03. We
inferred one space from the spec's layout and asked for all of it with FC03.
The client learns FC04, sharing a body with FC03 since the two differ only in
which table the server consults, and the plugin's two measurement reads move to
it. Writes stay on FC06, where the controls already live.
Confirmed against an A5191 on firmware 1.0.6.1: identity, live block and the
control registers all decode as the spec tabulates them.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
OCPP asks the charger to dial us: a public endpoint, a TLS certificate, and a
route in through the customer's router. Our own handler then demanded two more
things the V1 does not offer — TLS on a charger that connects over ws://, and
Basic auth credentials the Anker app has no field for — so every connection was
turned away before the upgrade.
Anker publishes a Modbus TCP register map for this charger, and it inverts the
problem: we dial the charger, on its own network, with no inbound reachability
to arrange. That works for a charger behind a router that OCPP cannot reach at
all.
internal/modbus is the protocol, hand-rolled against the spec like the MQTT and
WebSocket clients beside it. The plugin's modbus.go is the V1's map: the same
0-8 status enum the cloud already reports, per-phase measurements, and the
writable registers behind start, stop, current limit, boost and phase mode. A
new "modbus" control mode routes the existing control endpoints down it, so the
REST surface, the rate limit, the confirmation step and the audit trail are the
ones already there.
The commands the register map has no equivalent for say so by name rather than
failing as unknown, and a current below the charger's 6 A floor is refused
because it pauses the charge rather than slowing it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
