Developers geek talk – part 4
From day one we’ve had a love-hate relationship with the dongles. We love them being cheap, available, consumer-grade devices anyone can get on the cheaps and just use them. We hate the instability, how slow they are, the version issues and the complicated way to interact with them. They’re totally unusable to analyze what is going on on the CANbus.
When we started getting our feet wet and didn’t know anything about what was going on on the CANbus we started building our own hardware. Alex and Bob used AVR powered Arduino’s with an external CAN controller, I myself build a derivative of EVTV’s CanDue, based on a fast but not very popular ARM powered Arduino Due. Data was then pushed over serial (USB or Bluetooth) to a PC or tablet for further processing. This of course was totally not consumer rated, but it enabled us to really see what was going on in the car. There are some video’s on youtube of us struggling with that: the AVRs were lacking processing power, and the Due was more bulky and had to be hooked up to a PC using USB.
Fast forward two years and with the fast, small and WiFi enabled ESP8266 processor taking over the role of many AVRs in hobby projects, it was time for a new experiment. I connected a WeMos D1 Mini processor (bottom PCB) to a cheap external CAN controller board (top PCB) featuring an MCP2515, the bigger of the two chip and unfortunately a TJA1050. I had to either replace that chip with an SN65HVD230 or or modify the board a bit for 3.3 volt usage and choose the latter.
Be careful with the pin layout. The ESP8266 is VERY confusing: GPIO numbers, WeMos pin numbers, notation with D-prefixes and without. Most of that stuff is documented in the source code. Oh and I found a really tiny 12 -> 5V buck converter. It is minuscule, tucked away under the WeMos.
On the software side I started with the code for the http Bluetooth gateway, removed all code for Bluetooth and the dongle and added in code to use the CAN controller. This opened up a wealth of possibilities:
- Fast WiFi interface, fast direct PCI connection to the CAN controller
- Can auto-connect to the home WiFi network, or act as an access point;
- Very small footprint (4 x 6 cm PCB);
- No changes in CanZE and other tools needed as the http interface is exactly the same as for the gateway;
- Processor easily keeps up with the bus speed;
- Multi-frame handling (ISO-TP) completely offloaded to the ESP8266.
The device is more functional than an ELM327, completely programmable (watch this space for more functions beyond CanZE) and most of all FAST. You can see how fast here