433Mhz to IOT bridge

A project log for Standing desk remote control

Control multiple desks over wifi

lion-mclionheadlion mclionhead 04/29/2023 at 07:120 Comments

The leading contender for replacing IR pivoted to a central bridge that received 433Mhz FM from the CC1101 & transmitted on Wifi to all the desks.  The CC1101 definitely starts up fast enough.  There are 4 ESP8266's which never found any use in 5 years because they're too slow.  They only support wifi.  They would have to bind with the router.  Although they could become wifi on a raspberry pi's 2nd SDIO port, this was totally impractical.  Wifi desk control is what the rest of the world would do.

The hardest part is the 433Mhz connection to the router.  The router needs a bigger enclosure for all its radios.  The existing weather station radio needs a 433Mhz input.  It would merely translate the 433Mhz codes to legacy IR codes & forward them to the router.  The router would forward the commands through UDP.

The trick with the ESP8266's is they only do 3.3V.  The desks output 5V, so all the existing 16F1508's would have to stay as level translators.  The ESP8266's would just output the legacy IR code at 3.3V & the 16F1508's would be unchanged.  There could be a test to see if the desk pins handle 3.3V.  Then the ESP8266's could go in through resistors.  The 16f1508's are quite valuable.

New batch of boards begins for the 433Mhz conversion.  1 board was for a camera mount.  2 boards were for the desk control.  It's getting common for the etching process to create swiss cheese.  Not sure why this is.  It might be the age of the photoresist. 

Of mane focus was the new router board. Once again, the lion kingdom came a gutser for not having input capacitance for the voltage regulator even though these are all low power radios in receive mode.  The LP2989 is a finicky beast.

Note the 12Mhz crystal was referenced to 3.3V instead of GND.  This was a routing optimization unique to lions.  The router board involved an obsolete MRF49XA for 900Mhz weather station data, a CC1101 for 433Mhz desk commands.  A sane router would use single radio chip & have all the packets on 1 frequency, but these were the spare parts & simplest solutions.

The desk control blasts continuous RF like IR. The weather displays would lose packets & show -- when the desks were being commanded on 900Mhz.  The climate recording would lose packets but the climate recording has so much unused data, it wouldn't matter.  The desk packets could go at 10Hz with the transmitter off between packets, to give the weather data a fighting chance.

  Arbitration would require a much higher bitrate & 2 way communication.  The weather radios use 1 way 8192 baud in a failed experiment with minimizing power usage.  To share the radio with the desks, they would need 100kbaud & ACKs.  The desk control would need single button state change packets & ACKs if it was to share the weather frequency.  There would be a lot of investment all the way around.

Helas, much debugging revealed the last 2 CC101's had no transmit functionality.  They could receive from the Gu24 radio but not transmit.  They transmitted some kind of noise but not data.  Of the 6 original CC1101's, only 2 still worked & those were in the Gu24 controller.  It's not clear why they all died.  Historically, only 2 were ever used in RC cars.  2 flatlined in that role.  The power amplifiers could burn out if the antenna impedance isn't matched.