UART Protocol

F103 <-> EMW3165 UART Protocol

Working notes for the UART protocol between the STM32F103 sensor/display MCU and the EMW3165 STM32F411 WICED module.

This is the vocabulary map used by Rewair's local bridge firmware in wiced/apps/rewair/local_bridge/local_bridge.c.

Frame Format

Frames use:

*CMDLLLLLLLL\0field\0value\0...#

• CMD: four ASCII command bytes.
• LLLLLLLL: eight uppercase hexadecimal payload length bytes.
• Payload: NUL-separated fields.
• Trailer: #.

Architecture

• F103 owns sensors, local display state, score display behavior, and the LED matrix.
• F411/EMW3165 owns Wi-Fi, time sync, local network state, and cloud-facing behavior in the stock firmware.
• Rewair replaces the F411/EMW3165 application with a local bridge while keeping the stock F103 firmware in place.

Direction Groups

Likely F411 to F103 commands:

• NETW: network state, RSSI, IP, MAC.
• TIME: current time.
• TINF: timezone/DST information.
• DISP: display mode/preference.
• SLEP: sleep/display dimming state.
• NOTI: notification command.
• SUND: notification sound setting.
• KNCK: knocking gesture setting.
• ALRM: alarm command.
• TUTO: tutorial/demo command.
• MESG: text message command.
• LEDS: LED color/blink command.
• FDEF: factory default/reset command.
• DEBG: debug command.
• HASH, UPGR, DOWN: special update/control path.

Likely F103 to F411 messages:

• SENS: raw/processed sensor readings.
• SCOR: current score and derived sensor index/color values.
• REDY: sensor board ready.
• TEST: test result/status.
• TEND: test end.
• VERS: sensor firmware or product version string.
• SCCD: score/color code status.
• DVID: device id.
• MACA: MAC address.
• BTST: boot status or board test.
• RUNN: running/heartbeat state.
• SSID: Wi-Fi SSID status/request result.
• NETD: network down request/status.
• NETR: network restart request/status.
• BOOT: reboot/boot command.
• WVER: Wi-Fi firmware version request/result.
• SVER: sensor firmware version request/result.
• FNOW: firmware update now.
• WLOG: Wi-Fi log/status.
• WSTA: Wi-Fi state/status.

Some commands are request/response style, so "direction" means the side with clearly observed ownership in normal boot and telemetry flows, not the only direction the token can ever appear.

Vocabulary Table

Token	Likely direction	Purpose	Payload hints	Notes
NETW	F411 -> F103	Network state update	net, rssi, ip, mac	Lets F103 know whether networking is up and what address/MAC to display/log.
TIME	F411 -> F103	Wall-clock time	time	Needed for clock display and timestamped behavior.
TINF	F411 -> F103	Timezone/DST information	offs, dst_on, dst_off, dst_offs	Rewair currently sends Lisbon timezone data.
HASH	F411 -> F103, special	Firmware update validation	Update-path fields	Deferred until update behavior is deliberately implemented.
UPGR	F411 -> F103, special	Firmware update transfer/control	Update-path fields	Deferred for the MVP.
SCOR	Both / display feedback	Score and interpreted sensor values	score, color, index, sensor, temp, humid, co2, voc, dust	F103 accepts this to update the visible score. Empty index and sensor separators matter.
DISP	F411 -> F103	Display mode/preference	mode	Live test: frame DISP mode clock shows a clock; frame DISP mode default blanks the display on the current setup.
SLEP	F411 -> F103	Sleep or low-brightness mode	TBD	Not needed for the first local bridge.
NOTI	F411 -> F103	Notification	color/message/sound/display/mode-style fields	Related to user-facing notifications.
SUND	F411 -> F103	Notification sound	TBD	Not needed for the first local bridge.
KNCK	F411 -> F103	Knock gesture setting/action	TBD	Not needed for the first local bridge.
ALRM	F411 -> F103	Alarm	TBD	Not needed for the first local bridge.
TUTO	F411 -> F103	Tutorial/demo	TBD	Not needed for the first local bridge.
NOPR	Internal/no-op	No operation	None	Filler/default behavior.
MESG	F411 -> F103	Display text message	message, timeout	Try frame MESG message hello timeout 5; text/duration are not parser keys.
LEDS	F411 -> F103	LED color/blink	color, blink	Live test: frame LEDS color white blink 0 sets a steady white LED.
DOWN	F411 -> F103, special	Download/update state or network-down event	TBD	Ambiguous; deferred for MVP.
REDY	F103 -> F411	Sensor board ready	version observed	Important boot synchronization token.
TEST	F103 -> F411	Test command/result	mode observed	Boot/test lifecycle token.
TEND	F103 -> F411	Test end	TBD	Manufacturing/self-test vocabulary.
FDEF	F411 -> F103	Factory default reset	TBD	Keep disabled until reset behavior is understood.
SENS	F103 -> F411	Sensor readings	temp, humid, co2, voc, dust, light, raw values	Primary payload for Home Assistant/MQTT integration.
VERS	F103 -> F411	Version string	version text	May overlap with SVER/WVER request-specific tokens.
SCCD	F103 -> F411	Score/color code data	TBD	Name suggests score color code.
DVID	F103 -> F411	Device id	identity text	Local firmware can probably keep or ignore.
MACA	F103 -> F411	MAC address	MAC text	Identity/status path.
BTST	F103 -> F411	Boot/self-test status	TBD	Boot/test lifecycle token.
RUNN	F103 -> F411	Running state/heartbeat	TBD	Useful liveness signal.
SSID	F103 -> F411	SSID status/request	SSID text	Possibly lets F103 display current Wi-Fi name.
DEBG	F411 -> F103	Debug mode/log command	TBD	Useful for local experiments, not needed for MVP.
NETD	F103 -> F411	Network down request/status	TBD	Could request network teardown/reconnect.
NETR	F103 -> F411	Network restart request/status	TBD	Could request network restart.
BOOT	F103 -> F411	Reboot/boot command	TBD	Likely asks Wi-Fi module to reboot, or reports boot cause.
WVER	F103 -> F411	Wi-Fi firmware version	version text	Custom firmware should answer with its own version.
SVER	F103 -> F411	Sensor firmware version	version text	Sensor identity/status.
FNOW	F103 -> F411	Firmware update now	TBD	Deferred for MVP.
WLOG	F103 -> F411	Wi-Fi log/status	TBD	Diagnostics.
WSTA	F103 -> F411	Wi-Fi state/status	TBD	Present on the F103 side; not yet important to Rewair.

Minimal Local Bridge Scope

For a cloud-free firmware, keep the useful center of the protocol implemented and tested:

1. Parse inbound from F103:
   • REDY, RUNN, BTST for lifecycle.
   • SENS for local telemetry.
   • SCOR if mirrored by the F103.
   • NETD, NETR, BOOT for network/reboot requests.
   • WVER, SVER, SSID, MACA, DVID for identity/status queries.
2. Send outbound to F103:
   • NETW whenever Wi-Fi or local network state changes.
   • TIME after SNTP/local RTC sync and periodically after that.
   • TINF when timezone/DST configuration is known.
   • Optionally DISP, MESG, and LEDS for local controls.
3. Defer for later:
   • HASH, UPGR, DOWN, FNOW until the update path is intentionally supported.
   • Manufacturing/test commands unless the board refuses to run without them.

This is the current Rewair direction: make the EMW3165 act like a local MQTT/Home Assistant bridge while preserving the F103 sensor/display firmware.

Open Questions

• Whether SCOR is sent spontaneously by the F103 or only built internally on one side after SENS.
• Whether the F103 expects a boot script of NETW, TIME, TINF, version answers, or if those can arrive lazily.
• Which commands are mandatory to silence errors on the F103 display.
• Whether DOWN means network-down, download state, or both depending on payload/context.