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The more mature version of a HAN Port reader is available under the folder HAN_ESP_TSS721. The main difference in these two versions are that this one is using a proprietary (but simpler) circuit for the M-bus to TTL conversion and has very limited resources available for doing work on the schematics and PCB. The HAN_ESP_TSS721 is using a TSS721 circuit from Texas Instruments, specifically designed for M-bus to TTL conversion. Also all design is available for you in a KiCad format.
The design is using an opamp as a compined level converter and a schmitt trigger, in order to convert the HAN signal into a 3.3V compatible serial format. As the input levels on the opamp is much higher than our 5V supply, we are rectifying and smoothing the HAN signal to use for a supply here. (VDD)
As a power source, we've used a micro USB connector, providing 5V, just as this is cheap and easy. However, no part of the circuit will need any other power than the 3.3V, so any combination of power source and regulator that provides the 3.3V will do.
The ESP8266 setup is a rather standaraized setup and will allow for programming the ESP directly on the board, if needed. During programming, it might be neccessary to disconnect the incoming HAN.
- R8 should not be used
- The two unused inputs on the LM358 should be grounded (Pin 5 and 6)
| Name | Value | Part |
|---|---|---|
| C1 | 10uF/25V | P5148-ND |
| C2 | 100nF | BC1101CT-ND |
| C3 | 220uF/35V | 1572-1706-ND |
| D1 | 1N4148 | 1N4148FS-ND |
| P1 | 609-4613-1-ND | |
| P2 | Female | S7004-ND |
| P3 | Male | 952-2262-ND |
| P4 | 609-1047-ND | |
| Q1 | BC337 | BC33725TACT-ND |
| R1-5,10,11 | 10K | CF14JT10K0CT-ND |
| R8 | 100K | CF14JT100KCT-ND |
| R9 | 330R | CF14JT330RCT-ND |
| R12,13 | 47K | CF14JT47K0CT-ND |
| S1,2 | 450-1650-ND | |
| U2 | LM1117-3.3 | LM1117IMPX-3.3/NOPBCT-ND |
| U3 | LM358 | LM358NGOS-ND |
Note: The ESP8266 is not included here. It can easily be found on ebay etc