Panteltje's usa_pic page

Panteltje's usa_pic page


A RS232 to UDP Ethernet adaptor,
usa_pic stands for UDP Serial Adaptor - PIC
usa_pic is based on a PIC 18F14K22 controlling an ENC28J60 ethernet module from ebay (ebay item nr: 250799268967).




So what is the use of this "usa_pic"?
Well, it connects any RS232 based gadget you have to the internet, you can then send commands to it and read back data from it from anywhere (tm) 1).

1 )You need to enter the gateway MAC address in the source for now, and it is not tested, so best of luck,
I cannot test it, Vodafone blocks the return UDP port it seems.
But I can use it by doing a ssh to the local machine from anywhere, and then start netcat from there locally.
The RX side will work, use the NAT table in your modem to forward the UDP port.


Changes:
0.3:
the LM317 plus TIP 34 regulator is replaced by a LM2596-3.3 fixed switch mode regulator
No software changes, same bugs in version-0.3.
0.4:
Fixed error in buffer pointer calculation in subroutine 'read_byte_rx_buffer'.
Changed to IP 192.168.178.79 port 1079, and gateway for subnet 192.168.178.XXX (edit #defines in usa.asm for your situation).


A tgz archive with the asm source code for the 18F14K22 for gpasm, will likely not work without modification in MPLAB.
Click here to download usa_pic-0.4.tgz


The circuit diagram, old drawing, the 100nF cap in the switcher is not fitted:
This uses a LM317 based switcher to make 3.3 V for the PIC and the ethernet module, and a 7805 to make 5 V for the MAX232 chip.
The switcher is used because space is extremely limited in the small plastic box, and the heat dissipated in a linear regulator would melt it.

usa_pic circuit diagram


The hardware (old version with TIP 34 in the power supply), testing on the PC with a null modem cable, loopback mode, with netcat:



The box opened:



Top board filpped back, the 7805 has the tab cut off, not much current (heat) there:
boards top view


Boards botom view:
boards bottom view


Bottom of box:



Testing (with jppecat) and programming (with jppp18, and that thing on the right is my PIC programmer, based on a modified Noppp design),
I have taped some of the LEDs as those a blindingly bright:





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