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HP50g serial communication with 3rd party device
07-26-2015, 10:55 PM
Post: #10
RE: HP50g serial communication with 3rd party device
(07-26-2015 08:58 PM)Marakasmalan Wrote:  @snrowe: THANKS

OK, I will try these suggestions. Where can I find exactly wat the three different "Xlat" (I presume ASCII translation codes) does/imply?

I was under the impression Xlat refers to ASCII transfers, but I am not 100% sure. In any case I would try "None" for Xlat unless you know you want to translate characters. Not exactly sure on this one, suppose you could connect HyperTerminal and see what the HP50G sends with the different Xlat settings.

(07-26-2015 08:58 PM)Marakasmalan Wrote:  The device is a nad T748 avr amplifier receiver.

I will try the Hyperterminal and see how that work, however at the moment I only have my work laptop (on which I cannot install anything) that does not have a serial port, so I will get a USB - Serial converter before I can do that.
I've had limited success with the cheap USB to serial converters. You also may run into driver issues if you go that route.

I choose to use a serial to Bluetooth dongle to connect to modern devices. It's a bit pricey but works well and you can connect your hp50G wirelessly!
Aircable has some products for this. I use the aircable mini
Note you have to solder wire to power pin 9.
This particular BT dongle is very low power and will operate quite a while off a lithium ion battery.

(07-26-2015 08:58 PM)Marakasmalan Wrote:  Our brilliant goverment believes it does not ned to heed to advice, and consequently we now do not have enough power for the country. When the grid is overloaded, they impose "loadshedding", disconnecting areas off the grid on a predetermined roster. But when they switch it on again, the supply voltage is all over the show and it blew up my motherboard and power supply from my personal computer. Need to fix come next payday.

Where abouts are you located. Sounds like a big pain in the @!#$.

(07-26-2015 08:58 PM)Marakasmalan Wrote:  Some interesting observations:

Switching the device on and trying bufleng gives 0 and 1. Same happens when I try to clear the buffer as indicated in previous post.

OK I think I found the source of problems with the HP50g vs the HP48 when using this code. The HP50g has some issues using BUFLEN that the HP48 doesn't. Remove BUFLEN and use below:


.5 STIME @sets timeout for SRECV adjust per your needs
"Command" XMIT DROP @Sends command to AVR
10 SRECV DROP @Adjust 10 to the number of characters you expect. If you don't know how many set it to the maximum number of characters for the response. If the response is less it will wait STIME return 0, but the response will be above.

Uncommented below:
"Command" XMIT DROP

(07-26-2015 08:58 PM)Marakasmalan Wrote:  After sending a command, it does find something in the buffer. So something did come back. However, the avr did not execute the command that was sent to it.

What would have been the result if the pins on the serial cord was the wrong way round?

Incorrect wiring of pin 2 and 3 could be the issue. You may need a null modem to swap transmit and receive.

Sounds like a fun project. Hope some of this was helpful and you get it working.

FYI if you use a HP48G you might be able to use REMOTEBG to control this device via IR. I used to use an alarm to turn my HP48GX on and then my receiver on and play certain songs for my alarm clock in college.
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RE: HP50g serial communication with 3rd party device - snrowe - 07-26-2015 10:55 PM

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