Using TCM 310 transceivers in bidirectional low power
Contents
1. APPLICATION NOTE 409 Green Smart Wireless enocean EnOcean TCM 310 device default firmware is called GatewayController and it uses the ESP3 communication protocol Typical applications are line powered working as receiver transceiver which never sleeps therefore consuming gt 33 MA 3 V receiver on continuously One of TCM 310 less known because actually typical unused features for a transceiver is that it has a watchdog and it can be put in deep sleep energy saving mode through cor respondingly ESP3 serial common command CO WR_SLEEP for x milliseconds time peri od as shown below 1 10 53 Code 01 CO_WR_SLEEP Function Order to enter the energy saving mode Group Offset Size Field Warnes hex Description e a a ICOMMON_COMMAND 5 CO WR_SLEEP 1 n Period in 10 ms units 00000000 default max value max data range 00 FF FF FF 46h After waking up the module generate an internal hardware reset 11 BRE case the following RESPONSE message gives only the return codes RET_OK The device deep sleep current drops then below 0 3 uA meaning factor about gt 100k less vs normal mode a e Table 21 An issue is that in deep sleep the device can t neither receive nor transmit any messages neither over its radio nor over its serial interface The only possibility to wake up from deep Sleep remains its watchdog or a SOR Supply On Reset2. at 3 3 V device A so the VGS is below the threshold voltage and the MOSFET s are not conducting internal diodes also not because having on both side HIGH level This allows that the corre Spondingly I O lines on the master section B side are pulled up by its own internal pull up resistors to the same 3 3 V The I O lines of both sections stay HIGH 3 Now device A slave sends i e a message to the device B master through I O means temporary pulls i e down the correspondingly 1 0 line to LOW The source of the corre Sspondingly MOSFET becomes also LOW while the gate stay at 3 3 V IOVDD The VGS rises above the threshold and the MOSFET becomes conducting Now the same line on the master section side is also temporary pulled down to LOW by the device A via the conducting MOSFET The correspondingly I O line on both sections becomes LOW 4 Same situation but now device B master pulls temporary down the correspondingly I O line to LOW by sending i e a go sleep message to the slave Via the now direct biased drain substrate diode of the MOSFET the slave section is in first instance pulled temporary down until VGS passes the threshold and the MOSFET becomes conducting Now the I O line of the slave section is further pulled down to LOW by the B device via the conducting MOSFET The correspondingly I O line on both sections becomes LOW Conclusion the above described states show that the logic levels are correctly tr
3. The proposed circuit shows just one implementation example of this feature on a TCM 310 device used as transceiver in some specific bidirectional low power applications An energy balance respectively specific use case trade off should be made however before between two approaches a switching TCM supply voltage off between two communication cycles no deep sleep current at all but relatively long up to 500 milliseconds according user manual cold Start up time by same high current vs b keeping it instead in deep sleep mode by significantly faster start up few millisec onds depending on the required communication frequency e APPLICATION NOTE 409 Green Smart Wireless enocean Using TCM 310 transceivers in bidirectional low power applications In some low power applications like i e wireless heating valve actuators the device could be operated most of the time in deep sleep waking up only cyclical and for very short time frames to communicate with the system i e an ultralow power controller In this way high amounts of energy can be saved enabling the device to work powered i e by battery or even energy harvester The example below shows how to cut the UART lines of the EnOcean Dolphin based device during deep sleep in low power applications in order to avoid reverse residual currents and minimize accordingly the system current consumption Typical use cases are applications where a third part ultralow powe
4. ansferred in both directions of the UART independent who is the driving section A or B It also shows that during sleep the UART lines between slave and master are cut so no residual currents flow from VDD over the TCM I O s in this time The circuit complies with the Dolphin Core requirements regarding GPIO supply voltage in deep sleep mode and minimizes accordingly the current consumption of the system Note for correct operation the supply voltage VDD and IOVDD should be common i e 3 3 V for both devices master and slave With a Ves threshold voltage of about 1 V below the lowest VDD the circuit will operate properly If for example the lowest VDD is 3 V a threshold voltage Ves of maximum 2 V is therefore allowed Discrete BSS138 N channel En hancement Mode respectively BSS84 P channel Enhancement Mode small signal SMD MOSFET s both with low Ves are a good choice therefore R1 R2 and R3 can be very large typically merely MQ up to tens of MQ The screen shot picture shows the above described i t Pos 2260ne SAWE REC behavior Signals color green DVDD pink IOVDD Ezani s anannnnn nnnnnnnnn ssn Aktion yellow and blue the two UART lines 1 O s Sago eee From left to right both device are initially awaken ee E ee a TCM device receives on ADIO6 yellow the com ee a ee a a E mand Go sleep from the master It confirms im ee a ee Bilder mediately the received command ADIO7 blue to i M master and then it goe
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6. r microcontroller used as master cyclical communicates through UART with TCM 310 The ultralow power master drives i e a heating valve actua tor and is usually always on It communicates serial over very short time frames through the UART ESP3 protocol with the TCM device slave The device has an internal watchdog and sleeps most time The master is waiting then on TCM 310 wakeup readiness con firmed by the ESP3 CO_READY message communicates with for milliseconds and finally sends a new ESP3 CO WR_SLEEP for a determined time see above command on UART to the device This automatically confirms the received ESP3 command RET_OK and goes sleep for the given time wakes up then again and a new communication cycle starts In the proposed circuit Tl and Q1 are driven by DVDD to switch IOVDD supply voltage for all O s to VDD on during the communication and off thereafter The UART cutting circuit is identical for both I O lines and consists of N channel enhancement MOSFET s Q2 Q3 driven by the DVDD IOVDD Both MOSFET gates have to be connected direct to OVDD their sources to the correspond ingly I O lines on the slave A section side while their drains D to the same I O lines on the master B section side always powered common supply voltage VDD Note most MOSFET have the substrate internally already connected to the source otherwise this should be done externally The associate diodes bet
7. s sleep DVDD green fails ef A to Low followed with some delay by IOVDD a a pink and UART yellow amp blue While the master ete A A eae ane Speicher B is still on the TCM UART paths ADIO6 and ee ADIO7 are open during TCM sleep time right in picture bi S0 0rns q1r Feb 15 15 59 EnOcean www enocean com Subject to modifications Christian Bach Jun 2015 Page 3 4 APPLICATION NOTE 409 Green Smart Wireless enocean Remark Current TCM 310 FW are meantime optimized with regard to energy consump tion other as by formerly TCM 310 FW versions starting with version GATEWAYCTRL 2 11 0 8 TCM 310 FW release 14 and higher the receiver highest current consumption will be switched off immediately after receiving the command CO WR_SLEEP enabling additional energy savings Further Documentation https www enocean com de enocean_module tcm 310 https www enocean com esp https www enocean com dolphin core description https www enocean com fileadmin redaktion pdf app notes AN101 POWER SUPPLY LAY OUT 2015 pdf Disclaimer The information provided in this document describes typical features of the EnOcean radio system and should not be misunderstood as specified operating characteristics No liability is assumed for errors and or omissions We reserve the right to make changes without prior notice For the latest documentation visit the EnOcean website at www enocean co
8. ween drain D and substrate source S present as intrinsic n p junction of drain and substrate inside these MOSFET s play a key role in this circuit as shown below For the operation four states has to be considered 1 Device A TCM slave sleeps DVDD is 0 V T1 amp Q1 are blocked and the IOVDD path is conse quently not supplied by 3 3 V VDD Accordingly the I O of the slave section is in three state The gate and the source of the MOSFET are both three state so their Ves are below the thresh old voltage and both MOSFET are not conducting This allows that the UART lines at the master sec tion are i e pulled up by their own pull up internal resistors to 3 3 V The consequently invers biased integrated MOSFET di BSS138 odes are blocking however both BSS138 I O lines which are consequently physically interrupted between TCM A slave and B master EnOcean www enocean com Subject to modifications Christian Bach Jun 2015 Page 2 4 e APPLICATION NOTE 409 Green Smart Wireless enocean Using TCM 310 transceivers in bidirectional low power applications 2 Device A slave wakes up internal watchdog IOVDD is switched through T1 amp Q1 on to VDD 3 3 V consequently its I O lines are internally pulled up default As long as no device actively communicates pulling down the correspondingly I O side they remain HIGH the gate and the source of the MOSFET are both
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