Add unlock function and documentation for STM8S005.

Makefile

@@ -1,3 +1,7 @@
+CONTROLLER=stm8s105k6
+SDCC=sdcc
+STM8FLASH=stm8flash
+
 MAIN=main.c
 SRC=system.c systemtimer.c strings.c flash.c uart.c displays.c button.c encoder.c encoderbutton.c beep.c fan.c load.c adc.c ringbuffer.c
 RELS=$(SRC:.c=.rel)
@@ -6,17 +10,25 @@ all: bin
 
 bin: $(MAIN) $(RELS)
 	@mkdir -p bin
-	/home/dev/local/sdcc-3.6.0/bin/sdcc --std-c11 --opt-code-size -mstm8 -lstm8 $(MAIN) $(wildcard bin/*.rel) -o bin/
+	$(SDCC) --std-c11 --opt-code-size -mstm8 -lstm8 $(MAIN) $(wildcard bin/*.rel) -o bin/
 
 .c.rel:
 	@mkdir -p bin
-	/home/dev/local/sdcc-3.6.0/bin/sdcc -c --std-c11 --opt-code-size -mstm8 -lstm8 $< -o bin/
+	$(SDCC) -c --std-c11 --opt-code-size -mstm8 -lstm8 $< -o bin/
 
 clean:
 	@rm -rf bin
 
-flash: bin
-	/home/dev/local/stm8flash/stm8flash -c stlinkv2 -p stm8s105k4 -w bin/main.ihx
+#echo "0000ff00ff00ff00ff00ff00ff00ff" | xxd -r -p > misc/default_opt.bin
+unlock:
+	$(STM8FLASH) -c stlinkv2 -p $(CONTROLLER) -s opt -w misc/default_opt.bin
+	#$(STM8FLASH) -c stlinkv2 -p $(CONTROLLER) -u # Works only in stm8flash versions after git commit f3f547b4
+
+flash:
+	$(STM8FLASH) -c stlinkv2 -p $(CONTROLLER) -w bin/main.ihx
+
+eeprom:
+	$(STM8FLASH) -c stlinkv2 -p $(CONTROLLER) -s eeprom -w misc/eeprom.bin
 
 .SUFFIXES: .c .rel
 

README.md

@@ -7,24 +7,40 @@ The load can be ordered from China (AliExpress, eBay etc), something like this o
 
 ![The electronic load](docs/1.jpg)
 
-Added features:
-* full control via UART
+## Added features
+* full control via UART (connected to pins T and R)
 * calibration (via direct EEPROM programming)
 * parameters (e.g. minimal current) are changable
 * bootloader can be enabled
 
-I would recommend to not program the chip in the device, because:
-* then you cannot return to original firmware if you don't like this one
-* it's STM8S**0**05K6T6C, that means you can one program it about 100 times
-* you cannot user a simple USB-UART adapter to program it first time
+## Programming
+Programming the chip in the device has some drawbacks:
+* you cannot return to original firmware if you don't like this one
+* you cannot use a simple USB-UART adapter to program it first time
 
-Take rather a new (empty) STM8S**1**05K4T6C or STM8S**1**05K6T6C and solder it.
+Also the datasheet claims a write endurance of only 100 flash cycles but this is probably only for marketing purposes as it [contains the same die](https://hackaday.io/project/16097-eforth-for-cheap-stm8s-gadgets/log/76731-stm8l001j3-a-new-sop8-chip-and-the-limits-of-stm8flash) as the STM8S105 which is rated for 10000 cycles.
 
-Programmer connection:
+### Programmer connection
+Connect an STLink V2 to the pins at the bottom of the board:
 
 ![Programmer connection](docs/2.jpg)
 
-[Analog part schematic](http://www.voltlog.com/pub/dummy-load-sch.pdf) (one correction: PB3 is connected to +12V via 20k).
+### Flashing
+If you are using the chip which is already on the board you first have to unlock it via 
+
+    make unlock
+
+Then you write the new firmware with 
+
+    make flash
+
+and if you are flashing for the first time you also have to program the EEPROM:
+
+    make eeprom
+
+
+[Analog part schematic](http://www.voltlog.com/pub/dummy-load-sch.pdf) (corrections: PB3 is connected to +12V via 20k, R27 is 510 Ohm).
+[Full schematic](https://github.com/ArduinoHannover/ZPB30A1_Firmware/raw/master/hardware/schematic.pdf) (one correction: polarity of D6 is reversed).
 
 Calibration values in the code are for my instance, may be you have to adjust them for your one.