Alternate open-source firmware for the EA Elektro-Automatik PS 2300B power supplies
This firmware attempts to rectify a few issues mainly with the front panel operations of the PS2000B-series power supplies. The issues I encountered with the original firmware (my power supply was shipped with firmware version 3.06 dated 2018-12-27):
- The rotary encoders with their corresponding push buttons aren't always responding (at first I thought a few of the push buttons were faulty). Also no acceleration when turning knobs fast.
- Voltage setpoint can be adjusted in 1V or 0.1V steps, but the actual setpoints aren't matching up with the DAC steps sometimes leading to a setpoint 100+mV away from the one shown on the display. The setpoints are controlled using PWM outputs from the MCU which are heavily low-pass filtered. The original firmware outputs ~35kHz PWM which would correspond to ~11 bits resolution (72MHz MCU frequency / 35kHz = 2057 steps). For a 84V output supply this would in theory result in 84 / 2048 = 41mV per step. That's not the whole story though as there seems to be a 10% overrange margin (the setpoint for 84V output is around 3V, not 3.3V, so it's really 92.4V / 2048 = 45mV per step). There seems to be some additional rounding happening in the original riser firmware as stepping the output voltage in 45mV steps isn't possible.
- Voltage readback showing 84.00V (two decimals), but slowly decreasing the voltage will not update the display until it reaches 83.90V. Basically the last digit is always forced to zero leading to a readout that is almost always too low.
I asked Elektro-Automatik technical support about these issues and asked whether any more firmware would be released for these units and was told that there would be no further updates. Cue this alternate firmware. Note that it currently only supports the "triple" units with the blue/white segment displays! I have no idea how the single-output variants or the color touch models in the PS2000B series are put together at this point (and if they have the same issues). Input appreciated!
The triple output PS2384-05B supply consists of two PS2000 LT MC riser boards each controlling one power supply board. Both of these riser boards are connected to a single front panel board with all buttons and both displays on. The third output consists of a tiny riser board off of the second channel power board (not possible to control from the front panel MCU).
The riser boards controls their corresponding power supply using two analog voltages (one for voltage setpoint and one for current setpoint) and receives three analog voltages (voltage and current readback plus power supply temperature). Care must be taken to limit output power to the nominal rated power (voltage and current setpoints must not both simultaneously be set to maximum for instance, dynamic power limiting will take care of that).
The PS2000 LT MC riser boards normally boots their firmware from internal flash (and my modules reports version 406, or 4.06, firmware from way back in 2014). Due to the fact that the ISP mode pin, the Reset pin and the ISP mode UART are all connected to the front panel MCU this makes ISP boot possible.
I'm using the ISP mode and loading the alternate riser firmware directly into RAM which means that restoring original firmware operation is as simple as restoring the original firmware.bin file to the front panel (which does NOT contain any riser board firmware, it assumes that the riser will boot on its own).
The displays seems to use some variant of a Holtek HT1621 controller.
The front panel MCU is a NXP LPC1752.
Still a work-in-progress, the following front panel parts are working:
- SPI segment displays, 7-seg font and glyphs
- Keys and rotary encoder input
- Basic UART communication to the riser modules (send setpoints and receive readback)
- USB CDC ACM driver (just echoing data back to host)
- Rough initial NXP ISP support for RAM-booting the modules
- FreeRTOS up and running
- Tracking mode
- Preset button will show setpoints (setpoints will also briefly show when encoders are adjusted)
Front panel work in progress/not implemented yet:
- Retrieving more module data such as over-voltage/current (all stored in riser modules)
- Preset "menu", OVP/OCP, Lock
- USB communication protocol (SCPI perhaps?)
- Key debounce needs sorting out
The following riser firmware parts are working:
- UART communication (receives setpoints and sends readback, responds to queries)
- PWM outputs driving voltage and current setpoints (higher resolution than original firmware)
- Debug output over SWO
- ADC readback of voltage, current and temperature
- Constant Current indication
- Over-temperature shutdown/indication (may need some hysteresis)
Riser module in progress/not implemented yet:
- OVP/OCP shutdown
- Storing setpoints to EEPROM (after a timeout, limiting EEPROM programming cycles)
- Handle set property (like OVP/OCP), not sure if OVP/OCP should be committed to EEPROM
| Project name | Description |
|---|---|
| ps2k-front | Alternate PS2300 front panel LPC1752 firmware (includes the ps2k-riser firmware if compiled with ISP RAM-load support) |
| ps2k-riser | Alternate PS2000 LT MC riser LPC1315 firmware |
| lpc_chip_175x_6x | LPC Open files used by ps2k-front |
| lpc_chip_13xx | LPC Open files used by ps2k-riser |
Built using NXP MCUXpressoIDE 11.2.1.
- Import the four projects in a (new) MCPXpressoIDE workspace
- Build the ps2k-front firmware, this will produce the required firmware.bin file.
- Connect USB cable when power supply is off
- Hold
Ch1 PresetandCh1 On/Offbuttons while turning power on. - The power supply should appear as a
PS2000TUSB mass storage device. Make a backup of the originalfirmware.binfile! - Delete the
firmware.binfrom thePS2000Tdrive. - Copy the new
firmware.binfile to thePS2000Tdrive. I'm using the following on macOS:rm /Volumes/PS2000T/firmware.bin && cp -X firmware.bin /Volumes/PS2000T/firmware.bin && diskutil unmount /Volumes/PS2000T
Power cycle power supply. Done!
As always, no warranty (but works for me on a PS2384-05B supply).