Problem with lcd display module and Pira Rds Encoder

[Gus84]

Hello

My query is that I have the Pira rds encoder, and I built the LCD module. But the problem is that no data appears in the display. First I thought the problem was in the display module, but use the Spy Rds program using the sound card and does not get any data on the pc.
The RDS encoder works perfectly and upgrade to version 1.5d, so I wanted to tell me where I could be the problem.

Thank you very much and I hope I can help
Gustavo

Argentina

[Jan]

You write the encoder works perfectly so the LCD module must work perfectly as well. This is a purely digital world - 1 or 0 - LCD module built correctly or not. It's a few components so I'm sure you will finally have a success. The LCD module can be also ordered from us, 100% working and with warranty 

Note that some LCD modules use different pin order (always look at the datasheet of your LCD, don't buy a LCD without datasheet accessible).

[Gus84]

Thanks for responding. I understand, but I can not see the data that sent the I2C port on the PC using Rds Spy and using the sound card. Is there any way rule out that the problem is in the RDS Encoder?
If not I will be ordering probably the display module and also something else.

[Jan]

This is a little misunderstanding.  You can find the explanation in the RDS Spy manual, page 11. I'm doing copy & paste:

There exist probably tens of different serial buses based on clock and data signals carrying various data. The RDS serial bus based on continuous stream of 1187.5 bit/s is not the only one bus type ... RDS Spy cannot read other serial buses like I2C or SPI as these buses often does not carry the data required and use a communication speed of up to several MHz which exceeds capabilities of any sound card or serial port.

RDS Spy cannot read any data from 400 kHz I2C bus through sound card.

[radio maniac]

Yep same here, I've just finish building three Pira RDS encoders and three LCD displays to go with them - the RDS Encoders work great!!! However none of the lcd displays work? Scope the Data and Clock lines IIC shows very little or no activity except when the RDS Encoder is first powered up when the stored EEprom data is transferred to the CPU - It's as if the CPU doesn't recognized that the LCD are attached? I have gone over each display PCB several times and can see no fault with the wiring which is copied from the LCD Display manual! I'm at a total loss as to why they don't work, It's important for me to have the displays working as the RDS Encoders will be working as stand alone, I hope some one can shed some light on the problem - one thing to mention is when it's first powered up the top line of the display light up showing fully filled and after 3 - 4 seconds goes blank and nothing is seen since!

R Maniac.   

[Jan]

Adjust right contrast by voltage on LCD pin 3.

Some LCD modules require negative voltage on this pin - check with datasheet.

To determine if MCP23008 has been detected on the bus, type a command MEM DB in terminal. Bit 3 of the return value indicates whether the LCD is connected (1) or not (0). Since there's something changing on the LCD, I guess the problem is not here.

[radio maniac]

Not a problem with the contrast pot see att pictures, I will try the MEM DB bit,

R Maniac

[radio maniac]

OK tried MEM DB the reply was: reply: 4E

R Maniac

[radio maniac]

Different results every time see pic

R Maniac

[Jan]

Only bit 3 is relevant which is set to 1 so it's OK. In your circuit, signal wires between MCP and LCD are not connected correctly, causing the LCD receives invalid (blank?) data.

[radio maniac]

I will carefully check today the three display PCB's and make sure 100% they are wired up as per your P32LCD PDF and get back to you,

R Maniac

[radio maniac]

Hi Jan,

It's now all sorted! the problem was the connecting wire I used between the RDS PCB and display! I thought I was being neat by using 4 way ribbon cable! I simply changed them to individual connecting leads, It sounds a little crazy but  I guess this makes sense as there must be capacity coupling between the conductors of the ribbon cable corrupting the IIC signals! ( I looked at the MCP23008 data sheet which gave me the clue)
thanks for all your help and quick reply's Jan,

R Maniac

[Jan]

The IIC bus is an internal bus so it will probably not work if the connection lenght is a few meters, but there should be no reason for failure if you use say 20 cm of flat cable. Your encoder is a DIY version so check if you placed 2k pull-up resistors on the IIC bus (R10, R11). Increasing this value (for example to 10k) may result in the problems mentioned.

[radio maniac]

All the resistors are of the correct value of 2k 1% metal film and the flat cable was only 16 cm long, anyway it now works and now the fun can begin!

R Maniac