Re: New Driver: parallax

On 10.07.2012 08:25, Jeremy Blow wrote:
> On Jul 9, 2012, at 11:25 AM, Markus Dolze wrote:
>
>> On 07.07.2012 14:31, Jeremy Blow wrote:
>>>> Hi everyone,
>>>>
>>>> attached you will find a driver for Parallax serial displays:
>>>>
>>>> 2 rows x 16 characters Non-backlit with Piezospeaker (#27976)
>>>> 2 rows x 16 characters Backlit with Piezospeaker (#27977)
>>>> 4 rows x 20 characters Backlit with Piezospeaker (#27979)
>>>>
>>>> I wrote this driver some weeks ago on user's request, but didn't get any feedback if it works or not.
>>>>
>>>> So if it happens that you own such a device, please give it a try.
>>>>
>>>> The driver is still incomplete (misses documentation) and will not be committed for now until someone finds it is usable.
>>>>
>>>> Regards,
>>>> Markus
>>>>
>>> Hi Markus,
>>>
>>> I gave your driver a go with the latest from CVS. I'm running a 27977 off the motherboard COM1 header (ttyS0 in Ubuntu) with PIN3/5 through a simple circuit (NPN 2N3904 with 10K pull-up resistor on the RX line behind the NPN, and a 1K resistor ahead of the NPN base). I'm taking 5V off the floppy power lead from the PSU. Running Ubuntu 12.04 Server. Dips on the 27977 are set to on/on for 19200 baud. 
>>>
>>> Your patch compiled and installed fine, I configured LCDd.conf w/: 
>>> ===============
>>> [server]
>>> Driver=parallax
>>> ...
>>> [parallax]
>>> Device=/dev/ttyS0
>>> Speed=19200
>>> Model=27977
>>> Size=16x2
>>> ===============
>>>
>>> When I started the daemon (ps shows parameters as "/usr/sbin/LCDd -s 1 -f -c /etc/LCDd.conf", I received "\"'s across the LCD display filling the matrix. I also received the following in syslog:
>>>
>>> Jul  7 04:19:57 hostname LCDd: parallax: illegal Speed: 14; must be one of 2400, 9600, or 19200; using default 19200
>>>
>>> Seems like a simple typo somewhere, but was unable to trace it down yet. Not sure if related to display issue.
>>>
>>> Sending a character to /dev/ttyS0 via shell (echo -en '\x11' > /dev/ttyS0) several times causes an slash to appear as well. If I place the LCD in test mode (dips off/off), I receive the Parallax PacMan greeting (pretty cool).  
>>>
>>> Can you think of anything obvious I'm missing? New to LCD's and serial I/O, but happy to test further. 
>>>
>>> Thanks,
>>>
>>> Jeremy
>>>
>>>
>> Hi,
>>
>> I had a look at the speed selection code. Did I test that in the past?
>> Apparently not, the mistake makes me feel like a noob. Just missed the
>> 'break' statements. I made a new version that fixes this (see attachment).
>>
>> Anyway - that should have worked with your display if you set it to
>> 19200 baud.
>>
>> One thing you may try is to use 'Model=27976' as that is the same size,
>> but without the switchable backlight.
>>
>> Regards,
>> Markus
>>
> Hi Markus,
>
> Ah, makes sense. Since my last email, I went ahead and debugged further and found out I was having a voltage issue from my serial which prevented my circuit from going HIGH. As a result, the LCD was receiving many DEC(0)'s which the parallax interprets as '\' (a preprogrammed custom character). To save grief I ended up bypassing the direct serial and am using USB->Serial now with the Parallax and some python. 
>
> Regardless, I tested your v2 and the baud issue is gone. So two problems, two solutions. Retailers around here stopped carrying case modder type LCD's and are now only carrying the Parallax... so maybe we'll see more people try it. 
>
> Thanks for the fix!
>
> Jeremy
>

Hi,

those 'serial' displays are available from a number of companies
including Parallax, Sparkfun, and others. They are not really made for
PC use but for use with microcontroller boards like Arduino.

If one wants to use those with a PC, either a level converter or an
USB-to-serial bridge is (usually) needed. Summing up the prices for one
of those serial displays and an USB-to-serial bridge is close to a
PC-ready display like the Crystalfontz CFA-533. And the latter one has a
keypad!

On the other hand, if one wants to build a display himself, the LCD2USB
is much cheaper to build.

For these reasons I am not very confident in using those displays with a
PC and I don't own one (yet).

Regards,
Markus