Subject: PLX SM Pro + SM-AFR Daisy-Chain: DI1 (Boost) Raw 16-Bit Integer / Scaling Issue in KManager
Body:
Hey Hondata Team & Community,
I’m running a full digital serial integration of a PLX SM-AFR and PLX SM Pro module chain directly into a KPro over the 3.5mm digital serial input.
We have successfully established clean digital logging for Wideband (DI0), Oil Pressure (DI4), and EGT (DI7) on Instance 1 with the unit set to °F in KManager. The DM-6 gauges and the serial stream into KPro are both working great without dropping packets.
However, we are hitting a specific issue with DI1 (Vacuum / Boost) reading the SM Pro’s internal 3-Bar MAP sensor, and we are trying to understand why KManager’s internal digital parser isn't scaling the packet properly.
System Setup & Chain Configuration
* Hardware Chain: PLX SM-AFR (with termination jumper)
KPro Digital Serial Input.
* KManager Version: 4.6.1
* Working Digital Inputs:
* DI0: PLX Wideband
* DI4: PLX Fluid Pressure (Oil Pressure)
* DI7: PLX EGT (Exhaust Gas Temp)
The Issue with DI1 (Vacuum / Boost)
When mapping the SM Pro’s MAP sensor to DI1, KManager receives the raw serial stream, but displays an unscaled raw 16-bit A/D integer on screen instead of a calibrated PSI/inHg value:
* Key-ON / displays 4945.79 psi.
* Under approximately 6 PSI of boost, the raw integer value scales up to around 3200 / 3300.
Everything We Have Tried So Far
* Instance Testing:
* Tested Instance 0 and Instance 1 on DI1. (Instance 1 is required for the SM Pro EGT probe to parse on DI7).
* Channel Type Testing:
* Tested Channel Type set to Boost, Vacuum, MAP, and Fuel Pressure.
* When set to Vacuum, the reading remains an out-of-range integer.
* Unit Dropdown Tests:
* Cycled through every unit dropdown under Parameters > Digital Inputs for DI1: psi, bar, mbar, kPa, inHg, and inHg / psi.
* The displayed value remains in the high thousands regardless of unit selection, indicating KManager’s internal serial lookup table isn't applying a divider to the SM Pro's multiplexed pressure packet.
* Display / Sensor Setup Overrides:
* Checked Display > Sensor Setup properties. Unlike standard analog inputs, DI1 in KManager only exposes Display Min/Max, Warning Min/Max, and Units, but lacks a user-configurable Custom Scale / Math Formula multiplier box to divide down raw 16-bit serial integers.
Questions for Hondata
* Is KManager’s PLX Vac/Boost digital input decoder strictly expecting the legacy standalone SM-Vac/Boost module packet header (Address 0/1), or is there an internal baud rate / scaling lookup fix for the SM Pro’s composite 3-Bar MAP packet over serial?
* Is there a specific Channel / Instance combination for the SM Pro MAP stream over DI0–DI7 that we haven't hit yet?
* Could a future KManager update add a custom multiplier/divider input under Display > Sensor Setup for digital channels (DI0–DI7), similar to analog inputs, so raw 16-bit multiplexed serial integers can be scaled manually?
We know we can route the 0–5V analog signal wire from the SM Pro to AN0, but since the rest of the SM Pro array is logging 100% digitally over serial, we’d love to get DI1 mapped natively on digital as well.
Thanks for taking a look!
Kpro v4 plx sm pro digital input boost pressure
Re: Kpro v4 plx sm pro digital input boost pressure
Post the calibration used and datalogs showing the issue using that calibration.