Davinci Jr Repetier Port (Page 5 of 9)

Paging carl_m1968

We've got the majority of pins mapped, but I could use your help with the voltage comparator being used for the heater switch.

Pin 33 of the LPC1115 Microcontroller (U17) is attached to Pin3 and Pin6 of U9 (TSSOP8 package LM2903)
The NTC Thermristor appears to also be attached to U17's Pin33 (through R59 100Ω)
Pin 1 of U9 is attached (through R358 27Ω) to Q8's gate which controls the Heater circuit to ground

I'm uploading a close up of the voltage comparator circuit for you here

Admire what you guys can do. I have no idea how to trace pin or how these pins are named. Only have some basic electric knowledge. Will it be helpful to compare how duet wifi board achieve these function?
Also will it be helpful to obtain high resolution scan of the board so that we can label the trace in different color?

Does this make any sense?I have no idea exactly what they means, but googled some where mentioned LPC1115 Microcontroller can be used for JTAG. This might explain the function of U2. But I can not think of any reason why they want to use this approach, only data communication heavy part on the hot-end board is the auto-leveling. The other part is the NFC reader, which have no reason to reduce pin.

Reduced pin count JTAG (IEEE 1149.7)

https://en.wikipedia.org/wiki/JTAG#Redu … _1149.7.29

That's extract what JTAG do, it is kind of serial interface but not extract.The two pin interface is designed so that multiple chips can be connected in a star topology. one pin transfer serial data and the other pin send clock singal decide which device get the serial data, the star topology can explain your pin map confict--multple device hooked up to one pin:
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Reduced pin count JTAG (IEEE 1149.7)
Reduced pin count JTAG uses only two wires, a clock wire and a data wire. This is defined as part of the IEEE 1149.7 standard.[7] The connector pins are

TMSC (Test Serial Data)
TCKC (Test Clock)

It is called cJTAG for compact JTAG.

Example of JTAG with reduced pin count
The two wire interface reduced pressure on the number of pins, and devices can be connected in a star topology. [8] The star topology enables some parts of the system to be powered down, while others can still be accessed over JTAG; a daisy chain requires all JTAG interfaces to be powered. Other two-wire interfaces exist, such as Serial Wire Debug.

Communications model[edit]
In JTAG, devices expose one or more test access ports (TAPs). The picture above shows three TAPs, which might be individual chips or might be modules inside one chip. A daisy chain of TAPs is called a scan chain, or (loosely) a target. Scan chains can be arbitrarily long, but in practice twenty TAPs is unusually long.[citation needed]

To use JTAG, a host is connected to the target's JTAG signals (TMS, TCK, TDI, TDO, etc.) through some kind of JTAG adapter, which may need to handle issues like level shifting and galvanic isolation. The adapter connects to the host using some interface such as USB, PCI, Ethernet, and so forth.

ok, i have no idea what i'm talking about, just read something about people use LPC1115 for JTAG chip, and i thought functionally it make sense here. just keep this in mind in case you have trouble to understand the data you sniffed out.

No when I'm saying "M0" it's in reference to the cortex-m0 microcontroller, U17

Ah no you understood and I didn't in that context. I believe the uncontrollable heating is caused by the fact that the heating circuit being controlled by a voltage comparator circuit which is monitored by U17. Without reference voltage supplied by U17, the comparator circuit can't do its job which explains the heater behavior

does marlin support M4 ? I never saw it

We're missing the relationship between the main ATSAM (U2) and the Cortex-M0 (U17) which is handling the NTC sampling as well as the heater output PWM. The other functions attached to U17 appear to be non-essential.

Alternatively, a hardware rework could be performed to attach U2 directly to the heater's mosfet (Q8), but that's not exactly for the faint of heart, and certainly wouldn't be a mainstream option.

I'm gonna be putting together the serial sniffer tomorrow to see if I can capture anything useful between them

Ah darn, spaced on that little fact. I'm about 3 beers in so I'll poke around tomorrow.

i thought repetiter firmware dc42 is ardino based, it support duetwifi and duetethernet which use sam4e8e,
https://github.com/dc42/RepRapFirmware/ … uctions.md