Sunday, January 17, 2021

MQTT subscribe

A new 1.3.1 version of gateway firmware is committed to GitHub which is enabling MQTT subscribe functionality.

Gateway subscribe on topics: /OHS/set/#, particularly parsers following 

/group /{#} - index of group {1 .. ALARM_GROUPS}
  /state - allowed commands {disarm, arm_home, arm_away}
/sensor - allowed only for Input nodes
 /{address} - node address like W:2:I:D:1
  /value - float value send to remote node

To describe it better for someone new to MQTT.  MQTT is an open OASIS and ISO standard,  lightweight, publish-subscribe network protocol that transports messages between devices. The protocol usually runs over TCP/IP. It is designed for connections with remote locations where a "small code footprint" is required or the network bandwidth is limited.

For example:

/OHS/set/group/#/state topics is able to perform disarm, arm_home, arm_away commands for group index specified as #.

/OHS/set/sensor/{address}/value topics is able to receive float number that is then passed to appropriate node address.

Above subscribe and already existing publish functionality allow direct integration with mobile applications,  logging platforms for sensor data, or Home Assistant:

Saturday, January 16, 2021

New board revison, bulk buy, discount on 2.0.4 gateway

Last week I've received new 2.0.4 gateway boards. There are a few visible changes like connector description on silk screen and cut out hole for zip tie to hold on the RFM69 pigtail cable. And a few not so visible changes in routing and such, but none of them are really a reason to call it a new revision.

One problem that I've started to realize is relatively pricier GSM modem. The 2G/3G/4G SIM7600x are starting at 40EUR for regional and 50EUR for Global band coverage. I was looking for some cheaper alternative while still keeping at least 4G, and the apparent replacement seemed to be a new SimCom A7670x. Unfortunately these use different package, and are only covering Europe and China, still I deiced to give it a go and spun a new version of gateway. Just few days before sending it to fab I received a newsletter from SimCom that they released same modem module called A7600E which is pin compatible to one that gateway already use (7600X). One difference it is still Europe only and only 2G/4G. I think it is reasonable as 3G is, at least in Europe, being replaced by 4G/5G networks. Good thing is it requires only one antenna and it is 5EUR cheaper. I've ordered 2 units to test them.

For gateway, I have consolidated all the components, and I was able to get the price down by making bulk buy for all pricier components. Like buying the STM32F437 at RS Components, were it is 50% of my local distributor price.. This should reduce the final price to some 92EUR without a modem.