Custom filter board for the Radioberry

[Samuel Lourenço]

Hi,

I wish to design a tiny filter board with four LP filters: 10 m, 15 m, 20 m and 40 m. The board will just use three bipolar relays, one to switch from 10 m to 15/20/40m, other to engage between 15 m and 20/40 m, and a third one to switch between 20 and 40 m, in a cascaded configuration, so that the 10 m band is the one having the least contacts in line.

The fulcrum of the point is that I want to fully customize the OC in piHPSDR to suit my needs, and the manual suggesta that the N2ADR approach will override any setting I use. So, which I2C to GPIO should I use? The one in N2ADR or the one being used in Alex?

Kind regards, Samuel Lourenço

[SNAIL]

You can use any approach you want or like and use OC. To avoid N2ADR settings override just mark NO FILTERS box.

[Samuel Lourenço]

Thanks, Snail.

So, just to be clear, if I use the same I2C to GPIO expander as Alex in address 0x21, does that mean my OC options will be applied? Also, how will the IOs in the OC dialog map to the expander pins? I see that the expander has a total of 16 pins.

Kind regards, Samuel Lourenço

[SNAIL]

Yes, you can use GPIO expander 0x20, 0x21 or edit file filters.h in Radioberry  I2C board setup for LPF/BPF if you want to use different I2C expander. Yado-san suggestions are very helpful. 

In PIHPSDR menu RADIO set value in FILTER BOARD drop down "NONE". This setting will enable OC. In OC menu you have settings for RX BPF(left side) and TX LPS (left) side. I have custom filter boards and in OC menu I use only first 4 pins to have 9 filters after binary to decimal conversion. The rest of the pins just ignored as they are not connected.

[Samuel Lourenço]

Thanks! I will see what I can do.

Kind regards, Samuel Lourenço

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[SNAIL]

Just to make it clearer. Set marks as red dots placed. Ignore settings for my filters.

[Samuel Lourenço]

Thanks! By the way, the ored pins section, what is it for?

Kind regards, Samuel Lourenço

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[SNAIL]

I have no idea to be honest. It says for tuning. I think to enable band LPF during the tuning operation. I will check it today as I'm working on make transmission working.

[Samuel Lourenço]

Most probably, I'll have to use several gpios at the same time. Say:
1 2 3 4
[ ][ ][ ][ ] - 10 m
[x][ ][ ][ ] - 15 m
[x][x][ ][ ] - 20 m
[x][x][x][ ] - 40 m

This is due to how I'll implement the contacts of three bipolar relays.

Kind regards, Samuel Lourenço

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[SNAIL]

It depends on the electrical schematic. You have 8 + 8 output pins. TX and RX. In your case you have 

10m all relay off

15m relay1 on relay 2 and 3 off

20m relay 1 and 2 on, relay 3 off

40 meters all relays on. 

Don't forget to install relay driver, I2C chip can't take relay load.

BTW I don't see reason to use bipolar relay. It will make everything much complicated as you need to control two coils in one relay and bipolar relay is more expensive.

If you can post sketch of electrical diagram it could help to understand better what you trying to do.

[Samuel Lourenço]

Thanks. Yes, you got the sequencing correct. About the bipolar relays,
I mean relays that have two sets of contacts like the G6K-2P-Y-DC5. I
think you might be thinking about latching relays. I'll use MOSFETs to
actuate the relays, and I'm guessing that diodes might not be needed.

Since I will just be using pins 1 to 3, I think I might go with
MCP23008 at address 0x20, since it has a lower pin count and is more
compact, and the OC settings will be implemented the same, right?

Can I use the I2C from the Radioberry instead of using it directly
from the Raspberry PI?

I'm thinking about integrating the filter and a TX/RX relay on the
same board, and I can't see why not at that point. It will be less
flexible, but one less board. TX from the amp going through the
selected filter and then through the TX/RX relay on the same board.

Kind regards, Samuel Lourenço

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[SNAIL]

Ok, now it's clear. You just used wrong words for relay type. It's double pole not bipolar. Yes, you can use MCP2308 and ULN2003 or similar to drive relay. Everything else will be the same. I have almost the same design, filters boards have BDC and relay drivers. I put MCP2308, RX/TX relay controlled by PC817 optocoupler from CN301 Radioberry pin3. You can use I2C pins on same CN301 Radioberry connector, just install 10K pull up resistors on the back side to be safe. 

[Samuel Lourenço]

Thanks! I don't think I will need the ULN2003 or an optocoupler, as any MOSFET will work. I did it before when designing my TX/RX relay (you can search it here, on my "Radioberry Preamp supply weakness" post. In that case, I've used pin 3 to actuate the relay via MOSFET (maps to pin 4 on my board).

What was the address that you've used? 0×20?

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[SNAIL]

Yes, i'm using 0x20 address as it's MCP2308 address. ORED pins settings you can ignore, it's for communication with automatic tuner. Regarding MOSFET or chip preferences, I'm old and eyes and fingers not so good as it was. For me easier to use one chip instead of many tiny transistors plus resistors.  

Best regards.

[Samuel Lourenço]

On second thought, I think I will have to go for the PCA9555 at address 0x21. The fact that the MCP23008 may configure outputs as OC will complicate things, and depending on that the driver is doing I may get nothing.

So, change of plans, I will go for the PCA9555, despite having way more pins that I will not need, due to its inability of configuring pins as OC outputs. I need totem-pole outputs to properly drive the MOSFETs without needing extra resistors, and I wish to use N-channel MOSFETs instead of P-channel ones with some inverted logic.

Kind regards, Samuel Lourenço

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