PC to HP 48G infrared communication

[SammysHP]

I'd like to transfer data (libraries) from a PC to a HP 48G via infrared. I've already built a converter that receives serial data (2400 baud) and forwards it via IR. Sending ASCII data from the PC and receiving it via SRECV on the 48G works fine. But it seems that I lack the necessary knowledge to use Kermit.

What I've tried:

Code:

set modem type none
set port /dev/ttyUSB0
set speed 2400
set stop-bits 2  ; my serial adapter is configured for 8N2 and with just one stop bit the input buffer overflows
set carrier-watch off
set flow-control none
set parity none
set block-check 3
set control-character prefixed all
set file type binary

Code:

send FILE.lib

This is based on various tutorials that I found online, for example this one. But I'm not completely sure how to configure the 48G. I've set it to IR, binary, 2400, parity none, cksum 3 and then starting the kermit server via RS Right.

So my question is: How do I configure ckermit (9.0.302) and the 48G for this simplex connection to transfer libraries with error correction?

edit: If I SRECV the stuff from Kermit I get 36 bytes with "…kermit…" in it.

[cdmackay]

(02-23-2020 02:45 PM)SammysHP Wrote:  edit: If I SRECV the stuff from Kermit I get 36 bytes with "…kermit…" in it.

I'm not sure if this is relevant, but SRECV isn't Kermit. For Kermit I use RECV, but I'm using a wire; no experience with IR, sorry.

[SammysHP]

(02-23-2020 05:30 PM)cdmackay Wrote:  I'm not sure if this is relevant, but SRECV isn't Kermit. For Kermit I use RECV, but I'm using a wire; no experience with IR, sorry.

I know, that's why I said earlier "Sending ASCII data from the PC and receiving it via SRECV on the 48G works fine". I just wanted to test if anything is received and it was. Getting "kermit" in-between some binary data suggests that the data transmission is working, but that Kermit expects a response from the calculator (which is not possible because my IR connection works only in one direction).

edit: Maybe it is not even possible to do what I want. I thought Kermit supports unidirectional connections, but I might be wrong.

[ijabbott]

(02-23-2020 05:38 PM)SammysHP Wrote:  edit: Maybe it is not even possible to do what I want. I thought Kermit supports unidirectional connections, but I might be wrong.

Kermit supports half duplex connections (though possibly not on the calculator), but that still involves sending stuff in both directions, just not at the same time.

[cdmackay]

(02-23-2020 05:38 PM)SammysHP Wrote:  

(02-23-2020 05:30 PM)cdmackay Wrote:  I'm not sure if this is relevant, but SRECV isn't Kermit. For Kermit I use RECV, but I'm using a wire; no experience with IR, sorry.

I know, that's why I said earlier "Sending ASCII data from the PC and receiving it via SRECV on the 48G works fine". I just wanted to test if anything is received and it was. Getting "kermit" in-between some binary data suggests that the data transmission is working, but that Kermit expects a response from the calculator (which is not possible because my IR connection works only in one direction).

edit: Maybe it is not even possible to do what I want. I thought Kermit supports unidirectional connections, but I might be wrong.

ah! got it, sorry

[cdmackay]

(02-23-2020 05:38 PM)SammysHP Wrote:  edit: Maybe it is not even possible to do what I want. I thought Kermit supports unidirectional connections, but I might be wrong.

I thought that the protocol always required the receiving side to send ACK or NACK replies (even if data is only travelling in one direction), so I can't see how it can work with a one-way link.

[Christoph Giesselink]

The problem here maybe the ckermit program on the PC. When sending bytes over the IR port you may get IR reflections, that means that the byte you send is also received by your receiver. That's normally no problem, after sending the byte you just clear your receive buffer and you're ready to receive the answer of your request. The HP48 kermit implementation know this, so the IR transfer between two HP48 is no problem.

Most PC kermit programs don't clear the receive buffer after sending, because at a cable transfer they aren't aware about IR reflections.

Where I know from the reflections? The HP48 has an IR selftest and on a HP48GX/SX you can remove the port housing an so the cover over the IR transmitter. With removed housing/cover the IR selftest fails, but not with the mounted cover. The reasons are the IR reflections on the cover.

[SammysHP]

(02-24-2020 02:11 AM)Christoph Giesselink Wrote:  The problem here maybe the ckermit program on the PC. When sending bytes over the IR port you may get IR reflections, that means that the byte you send is also received by your receiver.

There is no receiver in my adapter. Sounds like I have to implement a receiver circuit. Project for next weekend?