W1209 Identifying 'compliant' boards
Note: buying a W1209 board today means drawing something from a grab bag! Besides the variants reported below, there are also reports of boards with slightly changed GPIO-LED assignment or unidentified µCs (i.e. neither STM8S003F3P6 nor N76E003AT20)!
Since the original forth implementation the W1209 boards have begun to morph into functionally similar but electrically different boards.
STM8 eForth currently provides binaries for the following variants:
- the original board with the two serial interface variants W1209 (two-wire serial interface through the sensor header) and W1209-FD (three-wire serial interface through keys)
- W1209-CA, a 1st variant with a Common-Anode (CA) LED display
- W1209-CA-V2, a 2nd variant with a Common-Anode (CA) LED display
Here then is a check list of what to look for when buying one of these boards.
This is a major show stopper. Only buy a board that has the STM8 micro on it. The Nuveton micro based board started appearing in late 2017 and while the pin out is identical this is not a ST clone but perhaps an 8051 derivative. It is not compatible with STM8 eForth.
If you can't read the lettering on the micro check for the presence of the indicated capacitor. This capacitor must be present for the STM8 chip to work, so if it is missing then avoid this board. Swapping the micro and adding the capacitor has proved one way to get them going. [When the board has the capacitor, STM8 should have 1.8V across the cap, as it is the regulator bypass capacitor]
Still available. Here is a pic of the two sides. Differences are marked on variations below.
Take note of the highlighted parts on the pictures which show the differences. Appears to have been re-routed and a slightly different relay used. Functionally identical to the original board apart from the resistor supplying the NTC resistor which is now 10k. On some variants a 5k resistor is found here too.
The presence of the isolation cut-outs around the relay, or differences in the silkscreen font and weight, simply point to a different manufacturer or production run. In themselves they do not discriminate between good or bad boards.
In early 2018 a common anode display was found on a board marked XH-W1209. A common anode binary was prepared and confirmed the board can be made to work, and the W1209-CA ("common anode") binary is now part of the GitHub Releases.
The difference between this variation and the common cathode varieties is very hard to spot and can only be seen on the rear of the board in the via's under the micro. Unless the vendor pics show the part number of the display (TUSO-02803-U is a common anode display) it is hard to tell! Those two via's on the common anode are displaced vertically ~3mm (in the pic's orientation), which is far greater amount than the ~0.5mm on the common cathode board.
At present as long as you get a board with an ST micro there is a binary version of STM8ef available to support it. The majority of boards are common cathode. Unless you knew you had a common anode board, first try the regular W1209-FD hex image when flashing.
It's also not difficult to trace the LED display pins to the STM8S003F3P6 GPIOs. Please write a ticket (issue) if you find something new! Converting boards from Nuvoton to STM8S is often possible, at least it's not harder than making and populating your own PCB.