EasyPIC4 w/ PIC16F688 at 12MHz with
rigged connection from hardware UART to on-board level shifter.

After some jiggery to get the PIC16F688 sample I received today talking to the built-in level shifter on the EasyPIC4 I had no problem getting the basic software for the HMLiberator running and responding to commands. It’s currently running at 12MHz, but as soon as I get some 20MHz crystals it’ll run there. This will give a baud rate just about 0.16% skewed from the specified 9600 baud rate, and I think that’s close enough.

I still have one problem to sort out before I try plugging it into the car, and that’s with the receive FIFO. With it set at the default of 40 bytes I can get five commands sent and responded to, and then the sixth just fails. As I was testing with a seven-byte command (and 7×5 = 35, just below 40), I think I’m hitting point where the FIFO wraps around (or something — I don’t understand it well enough yet). The incoming commands are of varying size, so I’m not really sure how to work around this yet.

At least I know where the problem lies. Once that is sorted (or whatever) I’ll plug the thing into the car and see what it does. If that goes well, which I expect it will after some basic software changes, I’ll finish up the v1.0 circuit / board design and order a run of boards and make up a first batch of five or so.

Hmm, the software for the HMLiberator^† is (almost) working. It seems to respond as I hoped five out of six times. The next time it just seems to not do what I want. I’m not sure how to debug it, though, as I can’t really trigger an interrupt with the device in hardware debug mode.

This might take some thinking.

That said, it’s time to go home and build the appropriate cable so I can actually sling it in between an iPod and the HML itself for once.

^† The HMLiberator is the PIC-based device I’ve been cobbling together to sit between the iPod and the Honda Music Link, translating the Mode 4 remote commands into Mode 2 commands. This will allow the user to keep using the controls on the face of the iPod, while the HML thinks it has one locked down and under its control.

Skynet SNP-9F40

Oh, tonight I also threw out an old (unused) SCSI disk enclosure I had in the basement. I figured that the power supply in it might be useful, so I opened it up. To my surprise I found two of the power supplies pictured above. (Side by side photos of the two here.)

That there is a Skynet SNP-9F40 (PDF), and it’ll take (according to that PDF) 90~264VAC as input, and spit out +5VDC (4A), +12VDC(3A), -5VDC(0.3A), and -12VDC(0.3A). I’m thinking this could be quite handy for both some of the music stuffs I’ve been working on (maybe even the 9090), or just as a benchtop supply. (I’ll probably mount one of them in an enclosure with terminals and a switch on it or something.)

There was also a filtered IEC-type mains input on there which I grabbed, some PC-type Molex power connector harnesses designed for connecting the power supplies to drives, brass stand-offs, and plastic clip-type spacers, all of which which may come in handy. All in all, a good salvage.

When this…

sendCommand(mode2, 0)
sendCommand(playButton, 0)
sendCommand(relButton, 0)

Which supposedly sends these commands…

const mode2 as byte[5] = (0x03,0x00,0x01,0x02,0xFA) 'Simple iPod Remote
const playButton as byte[5] = (0x03,0x02,0x00,0x01,0xFA) 'Play Button
const relButton as byte[5] = (0x03,0x02,0x00,0x00,0xFB) 'Release Button

Gives me this in the serial console…

Received: 0xFF 0x55 0x03 0x00 0x01 0x02 0xFA 0xFF 0x55 0x03 0x02 0x00 0x01 0xFA
Received: 0xFF 0x55 0x03 0x02 0x00 0x00 0xFB

…I know it’s time to go home.

And yes, as suggested earlier I just went ahead pre-calculated the checksums. I also just bundled the packet lengths in there too, and I read that first bit to determine how many bits have to be sent so that packets of arbitrary length may be sent simply by defining them as a constant.

It’s sending back to the PC properly, but not to the iPod. I think that’s because of some weirdness with the pins I chose to use. It worked fine on the PIC16F88, but for some reason that thing cooked this morning. (It now reports itself as some 12F part, likely indicating that some of the bits which indicate the part type have failed.)

Now to get the part running from the internal oscillator instead of a crystal and responding to commands from the serial port. (Both of these should be fairly easy.)

After that I can start building the list of responses I want sent to the Honda Music Link (initial by-hand decoding of a sample conversation between my iPod and the HML can be seen here). Then once that’s all set it’s time to plug it into the car and hope things work as designed. If that works it’s time to design the PCB and see about producing a dozen or so.

Thanks very much and for directing me to pointers, structures (even though I didn’t use structures) and the unknown-to-me mikroBasic manual.

Whenever I reset the PIC on my EasyPIC4 (photo gallery retired) my iPod toggles between pause and play.

I now possess the world’s largest iPod remote.

Code here…