BasicPI

Updated 3D Model 18.dec.2018

This is a bit more than a mockup since it is almost complete, but adding 15mm to an existing design is a lot of extra space. I turned the Hat so that the Raspberry PI Ethernet would be at right. Basically this is 35mm wider than a normal Hat, so it is still small for a 3KW Motor Controller.

Actually I now have some extra space so I can add in a few things. I ditched a RS485, but I would also like more sensors if I have pins/space available. I have a connector to connect 5V on PI to 5V from Motor. This enables MCU and Driver to have separate PSU. I can also add pins to mount extra capacitors behind on the left side. This will be perfect as they will be left of Raspberry PI or other Hat’s. I actually could remove the large 1000uF capacitors on top to save some Space, but lets see how it works out.

This is an unfinished 3D of MC4X60V50A or MC4X for short. I initially stated that I did not want this as a Raspberry PI Hat, but I do have SPI1 available + CAN is already planned. It would make a powerfully module + I could add an isolated GW as an add-on etc. The controller itself is more or less finished and the driver stages are mature design.

Firstly I don’t need to attach a Raspberry PI, but it would be a very powerfully stack to be able to add the 20++ modules I now plan. If I add the 40-pin GPIO at bottom-left I would get the RJ45 and USB’s of Raspberry PI 2/3 at left as an extension. This could work out very well – lets try it out and see where we end up.

Just to remind everyone – this Motor Driver support 60V @50A. It basically does so on all 4 independent drivers, so you can run 4 x heavy PWM/Solenoids, 2 heavy DC Motors, a 3-Phase BLDC Motor or a heavy stepper Motor.

This is an early mockup of a NB-IoT/4G/3G/2G/GSM Hat just to illustrate the space needs. My main concerns are signal quality on the antenna part as this module do not have a direct antenna output. Below is a PCB snap-shot showing the details of the antenna layout.

I really could have needed a 3rd layer here to completely isolate the antenna signal, but this has to do. The LoRa unit have antenna on the module so I can use a pre-made Antenna port air-with wire, but I will need to do something similar with the GPS.

SIM7020E also have a bigger brother with GPS in the module, so I will consider that as well. I have not sorted passive components and PSU yet – but, a 4G module is usually no wimp on sending, so I expect that much of the spare space I seem to have here will be used on special voltage PSU – not sure yet.

SIM808 that I used earlier is larger, cover only 3G, but it had GSM and PCM sound. The later is digital sound enabling voice services like IVR etc. The drawback with SIM808 was size and the need for 4V/3A as well as the 3G limitation.

The advantage of actual sound support is that we can make a remote doorbell unit directly connected with voice and video to your phone. I will however re-investigate that option using a different path because 300Kbps is actually sufficient for both a voice and video channel. Video will work with reduced frames per sec, but that is sufficient to see what is happening.

I drafted a GSM/GPS module some time ago, but I never ordered it as I decided to ditch that PLC design and pick up a smaller footprint. Time has changed so I want to make a new approach.

Using STM32F405RG as core I want to add NB-IoT, LoRa and GPS capabilities.

NB-IoT is a new 4G service allowing 300Kbps, low cost data links over mobile networks.

LoRa is Long Range radio and cover 433Mhz and 868Mhz modules to communicate up to 12 km with 300kbps speed.

GPS is as you know a system using satellites to detect position.

I want to make Raspberry PI Hat’s with these breakout’s. Looking into the practicalities I probably need 2 hat’s for this due to space restrictions. All three of these will need high frequency antennas, so I might for that reason alone need 3 Hat’s. Let’s see where we end up.

A natural infrastructure is that you use NB-IoT to reach remote places and then WiFi or LoRa locally. Both Wifi and LoRa units are secure these days. My real reasons for doing this has to be secret as I basically need these components for a test-bed/prototype and this is a great opportunity to add components to a modular Control system that is excellent for home automation and prototyping.

I want an Ethernet module to by list of boards. I can always use Raspberry PI 2/3, but I would still like to make my own as well. In the past I have used W5500 a few times, but this time I want to dig into ESP32.

ESP32 already have the TCP/IP stack, it has Wifi/Bluetooth and an Ethernet interface. A few vendors have also show schematics for Ethernet on ESP32, so it makes sense upgrading my ESP32 Hat with Ethernet. I do have the space if I drop the RS485 etc. A quick check also tell me that I have the pins as well.

The Raspberry PI Header can be sacrificed if I need to. CAN is the backbone bus and this is most attractive if I want to replace Raspberry PI as Wifi/Ethernet GW.

This Hat is not a priority, but I will make it at some point.

One of the challenges I face is that batches with MCU’s from Asia are dodgy. This has been specially bad on STM32F405RG so I want to make myself a MCU tester for Rx and Cx series. I just tried to wire one and it kind-off works, but SWD wiring get to dodgy so I need to make a proper PCB.

I have one of these laying around and have ordered a few more, but I need to remove the breakout board and mount it on a dedicated test PCB.

• Power and ground connected. Using a USB as power connector.
• VCAP capacitors with switch so I can test both STM32F1 and STM32F4.
• Led on all pins
• Proper SWD connector – short cables. Rather than the 1.27 header I can use a 2.54 and plug ST-Ling/V2 straight on the board.
• 8 or 16Mhz x-tal mounted.
• UART1 connected on a connector so I can run a standard application and display some test IO.
• Header rows for all pins.

It is so many functions on a STM32FxxxRx MCU that it is difficult to test them all, but the application above will get me airborne knowing that the MCU looks decent before I solder it on.

A STM32F405RG has a factory price of 5.8.- USD from ST and I would gladly pay that price, but before I receive a MCU from a distributor it cost me 17.- USD all included. So I use Asian sources. The challenge is that MCU factories also are in Asia and many people earn a few extra bucks by selling factory rejects. For prototyping many of these are “ok”, but then you have those that are not.

I faced the same issue with MOSFET’s earlier, but discovered that it was cheaper getting the MOSFET’s from Arrow so I had a bit of luck. Buying a STM32F405RG from Asia you get them down in 3.8.- USD these days. With a tester I can test them straight away and slam bad batches by claiming my money back and avoid the loss.

I will need to build the tester for each MCU, but I can probably sell of a few of these testers as well because I am not the only hobbyist or professional needing this and this type of equipment do cost money.

In fact, I can probably use 1-2 MCU’s to auto-test a 3rd MCU, but that us fun for later.

XPortHub feeding from Raspberry PI 3 A+ this time. 2nd board and 3rd MCU. The 1st MCU started behaving strange, so added a 2nd that did not work at all. Finally ripped off an old good one and we have a working board. Basically I need to make myself a tester for these MCU’s. Regardless, running fine at 168Mhz with USB working.

 This board can as mentioned be used stand-alone powered by USB, as an add-on to Raspberry PI or as a module in a stack of similar board interconnected with CAN.

I do love then things just work. This came up straight away – no coding, all generated from CubeMX. I need to add a few bits for this to actually work, but it is a first step. Lets see if we can get the rest of this cute Hat design alive as well.

The first 2 Hat’s of my new series arriving – I paid for the fast track because I will be assembling and testing these over x-mas. The PCB at left (above) and below is the XPortHub, the other is the ESP32 based Wifi Hat. The picture below is on top of a Raspberry PI 3 A+ and mechanics fits perfectly. Also the Micro SD card was perfect, so this looks good.

Final 3D with horizontal connectors. I might add a jumper to allow separation of 5V and Stepper V+. This can in theory drive 28 PWM channels up to 50V @ 500mA each, but the ULN2003’s overheat if we tried that.

I will add a proper PWM Hat later as this is dedicated for 5-wire stepper motors.