Back to gateway

I have used my recent W5500 breadboard friendly PCB to overcome problem with W5500 directly on gateway. As you may know there is problem with packed loss during transmission, which make it nearly impossible to further debug other parts. I have soldered ISP header on the gateway and used is as SPI to attach W5500 PCB. This works just great! I'm back to 100MHz full duplex Ethernet business. With improvements to Webduino library and some other tweaks, it have gained on speed towards web clients, as well as more time to process things internally in RTOS.

I have stared to test input blocks. Digital ones are same as on old gateway, and tere is no surprise. However analogue part was redesigned, but first test shows it works as expected. I will have to test further what over voltage or shorts it can withstand. I'm happy with that, because I'm more digital then analogue guy :), or better yet software type :D.

I have noticed that during uploading new sketches into gateway, I toggle the GSM module On and Off. This is a bit of drag as you imagine. It could be solved further in software, but I have rather done some changes on pin assignment.  I have tossed out GSM_RESET, as it can be reset hard way by switching GSM_POWER. And change it to input pin reading GSM state (GSM_STATUS). This way software can recognise instantly during start-up if the GSM module is already On or Off.

Next I will test outputs and RS485 interface. Then check power supply fall back and real time battery backup. If all goes well, I'll release final version of new gateway, which I plan to sell as starting point to DIY home security for anyone interested.

W5500 for sale

I have put the PCB and assembled board to store section on right. It offers all the function as W550io:

• Size 2.5 x 5 cm.
• Require 3.3V.
• 80Mhz SPI.
• RJ45 jacks with integrated magnetics.
• ACT and LINK LEDs.

Choose PCB only or fully assembled version.
Standard 0.1" pin header with GND, 3V3, SS, SCK, MISO, MOSI, RST, INT pins.
Schematics are added for download.

W5500 test PCB progress

PCB arrived on Monday and Tuesday I put it together. Say it short, it works. Happy again, I can continue with testing of new gateway. The differential pairs design worked, and the 33R dumping resistors are not required. Moving 3V3 power line out of RX and TX pairs probably also. Results is having a nice 2,5x5 cm breadboard friendly W5500 board. I will put PCB and finished version also to BUY section on right side. Maybe someone is interested.

W5500 test PCB

As gateway board is having issue with Ethernet crosstalk, I have created small 2.5 x 5 cm breadboard friendly PCB. I will use it to verify my new component arrangement and not spending another 50 USD on full gateway boards. I used differential trace length and moved the 3V3 power line away form TX/RX pairs. Also I have removed 33R dumping resistors from design as I have not found them anywhere else nor even or W550io from WizNet.

Gateway progress

I have all components at home and I started already some tests. There are good results and bad results as well.

I'm happy to say, that my UART mux is working as I wanted it to work. There are 2 UARTs on ATmega1284P, one is used for GSM modem and second for RS485. Both need to be connected to hardware serial in order to have queue, interrupts  and other capabilities. But I keep compatibility with FTDI Arduino programmer, so I miss 3th serial. First I wanted to put jumpers to redirect serial 0 to GSM or FTDI, but later I have found nice little IC 74LVC1G3157 that is able to mux and demux one digital or analogue line to 2 outputs in both direction. With using the 3.3V present in FTDI it switches automatically from GSM to FTDI any time you connect the FTDI to header. Nice little trick.

New GSM module is working well, I have switched from external SIEMENS to more common SIM900. It did not send SMS, and I was not able to read extended status, but it was all matter of slightly different responses of the 2 modems to same AT commands. Some "/r" or adding empty line in library and all started to work. One thing that needs to be corrected on PCB for SIM900, is the placement of capacitor near GSM antenna connector. If one will put it in position toward the capacitor bank it can, with some bad luck, accidentally short 4V and ground. Hot glue will do will do for now, but I will move the capacitor 2-3 mm away. There is also SIM900 RESET connected to ATmega, which is most most probably unnecessary. I think rather to use it as input of  SIM900 STATUS to quickly see if module is ON or OFF.

Now the bad news, the Ethernet part is not working well, I keep on losing ACK or packets. Sadly I was expecting some problems there, as it requires differential traces tuned to some impedance and EMI reduction, I have sent the finished gerbers to friend to evaluate. Well, it turned out I have cross talk after the PHY. I'm absolutely not expert on such design, and I have no such equipment to debug 100Mbits Ethernet. But I have very slowly eliminated all to this hardware problem. Also lowering the speed to 10Mbits fairly lowered the error rate of my packets. All that is left is to try another brand MAGJACK.

All bad is for some good, I have tuned up Webduino code and W5500 library to use maximum bandwidth, and the embedded web server is now pretty fast, rising to over double the speed.

Rest is fine, I will just test the ADC protection circuit. For W5500 I will most probably design small 2,5 x 5 cm breadboard friendly PCB, not to waste another $50 for whole gateway board.

My setup

As promised to Dan, here is picture of my current setup.You can see mainboard(GW) with attached Wiz820io on it. Then GSM modem on right side. 868MHz antenna connector on top. Cables from PIR, smoke and GBS sensors in the middle.Lead Acid Rechargeable Battery 12V, 7.2Ah in bottom left corner and Meanwell switching power supply PSC-60-C. All mounted in metal box enclosure with tamper switch. As I work on new version now and not changing the software, it shows uptime "79d, 23:57:40".

Remote (door entry) units are connected also by wire cables (RS485 protocol) and there is already short video, how they work.

PCB is here

New PCB version 1.6. is here, and I have started to put all components on it. All I had at home already is there and it is good so far. New switching power supply is delivering right around 4V required for SIM900. GSM module is starting up and when I put SIM in the socket it registers automatically to home network. W5500 also lights up the ACT and LINK leds when Ethernet cable is plugged it. I have to wait mainly for the UART multiplexer/demultiplexer to really start the tests. Waiting for you Mr. Postman :).