This repository is there to build an open-source firmware for the 60W ZPB30A1 electronic load (often sold as "60W electronic load" without any article number).
- Modes
- CC: Constant current
- CR: Constant resistance
- CP: Constant power
- CV: Constant voltage (slow regulation due to hardware limitations)
- Easily usable menu system with many configuration options
- Logging of all operating parameters via UART.
- Much better accuracy than stock firmware.
- Clean firmware structure for easy extendability.
The original firmware has read out protection enabled. Therefore you can't go back to this version once you flash a different one. But this firmware aims to be much better in every possible way. If you need a feature either add it on your own and submit a pull request or open an issue and wait till I add it.
This software requires Small Device C Compiler (SDCC) version 3.8 or higher (3.7 sometimes crashes during compilation).
The datasheet of the STM8S005 claims a write endurance of only 100 flash cycles but this is only for marketing purposes as it contains the same die as the STM8S105 which is rated for 10000 cycles. So you don't have to worry about bricking you device by flashing it to often. Mine has far more than 100 cycles and still works. You can easily verify the two chips are the same as you can write the whole 1kB of EEPROM the STM8S105 has instead of only 128 bytes as claimed by the STM8S005 datasheet.
As the original firmware has the bootloader disabled you need a STLink programmer in order to unlock it. Connect it like this:
If you are programming the chip for the first time you have to unlock it. '''WARNING:''' This irreversibly deletes the original firmware.
make unlock
Then you write the new firmware with
make flash
and if you are flashing for the first time you should also clear the EEPROM:
make clear_eeprom
Contrary to the original firmware which requires rebooting to change modes this firmware is completely configurable by an integrated menu system. Push the encoder button to select an item. The "Run" button acts as a back button in most situations. Only in the top level menu it is used to enable the electronic load. The currently selected option blinks. When setting a numeric value the two LEDs between the displays show the selected digit. Values shown with a decimal point are in the unit shown by the LEDs or on the display. If no decimal point is shown it means the display shows 1/1000 of the selected unit.
- 10.0 + V LED: 10.0V
- 1.23 + A LED: 1.23A
- 900 + V LED: 900mV = 0.9V
- MODE
- CC: Constant current (default)
- CV: Constant voltage
- CR: Constant resistance
- CW: Constant power
- VAL: Sets the target value for the currently selected mode. The upper display shows the unit.
- ILIM: Current limit (not active in CC mode)
- ...: More settings
- BEEP: Beeper on/off
- CUTO: Undervoltage cutoff
- ENAB: Enable/disable
- CVAL: Cutoff value in Volt
- MAXP: Maximum power action
- OFF: Turn off load when the required power would be greater than the hardware limit
- LIM: Reduce load current to stay within hardware limits
While in run mode the top display show V, Ah, or Wh. The bottom display show the current. The unit in the top display switches automatically after some seconds. Rotating the encoder changes the unit manually and disables automatic switching. Pressing the encoder enters a menu to change the current setpoint without exiting run mode.
- OVP: Over voltage protection. Voltage connected to P+/P- is too high. (Note: This function can only warn about voltages which are slightly to high. Large voltages will destroy the electronic load!)
- OVLD: The load can't maintain the set value. Usually this means that the source can't deliver enough current or the source's voltage is to low.
- PWR: Power required to maintain the setpoint is greater than hardware's power limit.
- TEMP: Temperature is to high. Check if the fan is working and the thermistor is connected.
- SUP: 12V input voltage is too low. Connect better power supply.
- INT: Internal error. Should not happen. Check the source code where this error is set and try to fix it.
Command can be sent to the device over the serial port. All settings can be modified and the load can be enabled and disabled. A help system is included. Send HELP or command HELP for details. The code is designed to be easily expandable if you need to add more commands.
Set the operating Mode of the electronic load.
- CC = Constant Current
- CV = Constant Voltage
- CR = Constant Resistance
- CP = Constant Power
Set the target amperage for constant current mode.
- mA = Target amperage in milliamps between 200 (0.2A) and 10000 (10A)
Set the target voltage for constant voltage mode.
- mV = Target voltage in millivolts between 500 (0.5V) and 30000 (30V).
Set the target resistance for constant resistance mode.
- mR = Target resistance in milliohms between 10 (0.01 ohms) and 15000 (15 ohms)\n"
Set the target power for constant power mode.
- mW = Target power in milliwatts between 0 and 60000 (60W)
Enable or disable alarm and notification sounds.
- OFF = Turn off alarms and notifications
- ON = Turn on alarms and notifications
Target cutoff voltage. If the voltage falls below target, the load will be disabled.
- mV = Cutoff voltage in millivolts between 500 (0.5V) and 30000 (30V)
- OFF = No action will be taken if voltage falls too low
Set current limit. If this current is exceeded, the load will be disabled.
- mA = Amperage limit in milliamps between 200 (0.2A) and 10000 (10A)
Set action to take if maximum power limit is exceeded.
- NOLIMIT = No action is taken
- LIMIT = Load will be disabled if power limit is exceeded
Requests the load to activate or deactivate.
- ON = Activates the load
- OFF = Deactivates the load NOTE: ON is similar to pressing the run button and will take you up one menu level. It will only enable the load if you are at the top menu level. Send multiple LOAD ON commands until you see the realtime output indicate the load is on. NOTE: OFF disables the load but does not return you to the menu. Use the hardware run button if you need to get in to the menu
Requests current settings.
Set log type.
- HUMAN = Human readable
- ESP = Formatted for ESP logger
- DEMAND = On demand by command GETLOG
Requests log
This firmware started as a project to extend the firmware written by soundstorm but it turned out as an almost complete rewrite which keeps the user interface idea.
Schematic can be found in [hardware/schematic.pdf].
- R5 = 10k
- R27 = 1k
- D6 = reversed polarity
