I bought a used Easytouch PSL4 system online that came with a universal outdoor controller (uoc) and a universal indoor controller (uic)... and since I needed an Easytouch 8 uic for my test bench, I figured I'd try and hack the PSL4 unit into an ET8.
I knew the outdoor boards use the same basic hardware across all versions but I'd never bothered to look at the indoor controllers. I took apart the PSL4 and laid its main board side-by-side with one from an ET8 indoor controller... predictably, they both had the exact same hardware. So how does it know it's a PSL4 or an ET8?
Sometimes it's just a simple matter of swapping firmware, but hardware designers often employ a hardware-based means of identifying the version, which then dictates what features the software allows. In the case of the indoor controllers, the main boards are exactly the same - no different resistors or jumpers - but I did notice some keypad differences.
As it turns out, there's a trace on the keypad that identifies the device as a PSL4. When the controller starts up, the firmware checks the status of pin 4 to see if we've got a PSL4 controller. So let's carefully cut the trace with an exacto knife...
After cutting the keypad trace and updating the firmware to 2.160**, the Software Revision now reports that this unit is an Easytouch 8 running 2.160.
**The early PSL4 firmware used a different "s19" file than the other ET4/8 controllers, but since 2.160 it's been combined to a single file - so that's what I used here.
This modified indoor controller will now work as an Easytouch 8 with my outdoor board... it can program extra schedules and timers which is what I was hoping for. It does still only have 4 buttons, but if really needed more, I could mount some switches, wire them to the keypad connector, and make one last keypad modification.
There's a loop trace from pin 1 to pin 2 that identifies the controller as having 4 or 8 buttons... on an 8 button keypad the loop trace is broken, but it is in-tact on a 4 button keypad. I didn't cut the loop trace on this particular controller, but if I had the controller would illuminate the LEDs for aux circuits 4-7 when they are active.
Below is an 8-button keypad cut off a wireless unit, showing the hole that breaks the loop trace... you could of course do the same thing with a blade.
UPDATE:
I have since performed the same "hack" on a PSL4 wireless controller... it's a little more difficult because the shell is fused and cannot be disassembled. I ended up drilling a small hole in the back, above the trace at pin4, in hopes of cutting the trace with a small drill bit or blade. I had another non-working wireless controller laying around that I used to locate the hole, so try at your own risk!
I knew the outdoor boards use the same basic hardware across all versions but I'd never bothered to look at the indoor controllers. I took apart the PSL4 and laid its main board side-by-side with one from an ET8 indoor controller... predictably, they both had the exact same hardware. So how does it know it's a PSL4 or an ET8?
 |
| Here's the Software Revision of the unmodified PSL4 uic |
Sometimes it's just a simple matter of swapping firmware, but hardware designers often employ a hardware-based means of identifying the version, which then dictates what features the software allows. In the case of the indoor controllers, the main boards are exactly the same - no different resistors or jumpers - but I did notice some keypad differences.
As it turns out, there's a trace on the keypad that identifies the device as a PSL4. When the controller starts up, the firmware checks the status of pin 4 to see if we've got a PSL4 controller. So let's carefully cut the trace with an exacto knife...
 |
| Pin 4 is 4th from the left, Pin 1 is indicated by the arrow. |
After cutting the keypad trace and updating the firmware to 2.160**, the Software Revision now reports that this unit is an Easytouch 8 running 2.160.
 |
| We've now got an Easytouch 8 controller (there are still only 4 buttons!) |
**The early PSL4 firmware used a different "s19" file than the other ET4/8 controllers, but since 2.160 it's been combined to a single file - so that's what I used here.
This modified indoor controller will now work as an Easytouch 8 with my outdoor board... it can program extra schedules and timers which is what I was hoping for. It does still only have 4 buttons, but if really needed more, I could mount some switches, wire them to the keypad connector, and make one last keypad modification.
There's a loop trace from pin 1 to pin 2 that identifies the controller as having 4 or 8 buttons... on an 8 button keypad the loop trace is broken, but it is in-tact on a 4 button keypad. I didn't cut the loop trace on this particular controller, but if I had the controller would illuminate the LEDs for aux circuits 4-7 when they are active.
Below is an 8-button keypad cut off a wireless unit, showing the hole that breaks the loop trace... you could of course do the same thing with a blade.
 |
| Notice the hole in the pin 1-2 trace loop on an 8 button keypad. |
UPDATE:
I have since performed the same "hack" on a PSL4 wireless controller... it's a little more difficult because the shell is fused and cannot be disassembled. I ended up drilling a small hole in the back, above the trace at pin4, in hopes of cutting the trace with a small drill bit or blade. I had another non-working wireless controller laying around that I used to locate the hole, so try at your own risk!
 |
| Carefully drilled hole in the back |
After drilling the hole, I was just able to use the tip of a small xacto blade to scrape open the trace at pin 4. I could seal up the hole with epoxy, but this is just a test unit so I haven't bothered. Nevertheless, it's recognized as an Easytouch 8...
 |
| Easytouch 8 running 2.160 firmware |
I now use this remote for testing the newer transceiver cards that are used with the Easytouch and Mobiletouch 2 (these are the Laird chipset based units). Again, it's only got the 4 buttons but I don't need more than that.
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