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swr_bridge.ino - Initial Success

Steve Beckman All Messages By This Member #101981 Dave - I opted to run the digispark from 3.3 Volts. The 3.3V, Ground, SCL, and SDA signals were all grabbed from the exposed pins at the RTC Module. Current drain is <10 mA. I still may put a separate 3.3V regulator on the board to reduce power dissipation in the existing 3.3V regulators. The digispark module seems to be happy running at 3.3 Volts at 16.5 MHz. The ATTiny85 spec sheet indicates this is probably pushing the speed ratings a bit, so I'll have to try selecting the 8 MHz clock option in the Arduino IDE. Anyway - without the digispark module connected, I get the expected "i2cbb.c: writing address failed at 8" messages on the console during transmit. With the module connected, those errors are no longer printed to the console during transmit. So the sBitx software is now getting a response to its commands on the i2c bus at address 8. I can also tickle the ADC inputs on the digispark module with my finger, and cause the Power and SWR readings to change on the GUI - which means the little module is working! That's enough for one evening. I have the SWR Bridge built and ready to wire in, so the next step is to get the Bridge interfaced and calibrated. After that it will be time to experiment with code fixes. Looks like this will be a viable way to add Power and SWR measurement functionality to the sBitx DE. 73; Steve, N3SB
Ashhar Farhan All Messages By This Member #101982 Steve, The "polarity" of the L402 , the transformers is important for it to work properly. It will either add or subtract from the phase of L400 depending upon which way the winding goes. We are also experiencing some differences between germanium and silicon detection diodes. The calibration needs a single variable bridge_compensation. The code is in read_power() function of sbitx.c.? This is in the later commits. - f toggle quoted message Show quoted text On Wed, May 3, 2023, 6:18 AM Steve Beckman <n3sb@...> wrote: Dave - I opted to run the digispark from 3.3 Volts. The 3.3V, Ground, SCL, and SDA signals were all grabbed from the exposed pins at the RTC Module. Current drain is <10 mA. I still may put a separate 3.3V regulator on the board to reduce power dissipation in the existing 3.3V regulators. The digispark module seems to be happy running at 3.3 Volts at 16.5 MHz. The ATTiny85 spec sheet indicates this is probably pushing the speed ratings a bit, so I'll have to try selecting the 8 MHz clock option in the Arduino IDE. Anyway - without the digispark module connected, I get the expected "i2cbb.c: writing address failed at 8" messages on the console during transmit. With the module connected, those errors are no longer printed to the console during transmit. So the sBitx software is now getting a response to its commands on the i2c bus at address 8. I can also tickle the ADC inputs on the digispark module with my finger, and cause the Power and SWR readings to change on the GUI - which means the little module is working! That's enough for one evening. I have the SWR Bridge built and ready to wire in, so the next step is to get the Bridge interfaced and calibrated. After that it will be time to experiment with code fixes. Looks like this will be a viable way to add Power and SWR measurement functionality to the sBitx DE. 73; Steve, N3SB
Steve Beckman All Messages By This Member #101984 Farhan - the SWR Bridge board I have has two small potentiometers for adjusting the output voltage of the forward and reflected readings. The detector diodes are 1N5711 schottky diodes. Looks like you have selected 1N63 Germanium diodes for the detection circuitry in the V2. It would not be difficult to for me to swap the 1N5711 diodes out with 1N34 Germanium diodes if the voltage vs power curve difference becomes an issue. I see a potential issue with the digispark module in that it's USB bootloader has a 1.5K pull-up resistor on the ADC3 input pin. I may need to have a #define in the Arduino code to change the ADC input from ADC3 to ADC1 if a digispark is being used. The other option would be to remove the 1.5K pull-up resistor from the board, and install one in a USB extender cable that's dedicated to programming the digispark. I'm not expecting that it will need to be programmed all that frequently, but the capability to do so needs to be maintained. 73; Steve, N3SB
Ashhar Farhan All Messages By This Member #101986 Steve, We are not shipping with 1N4148s. The germanium diodes are getting scarce and the schottkey diodes are a bit expensive for the scratch builders. - f toggle quoted message Show quoted text On Wed, May 3, 2023, 7:31 AM Steve Beckman <n3sb@...> wrote: Farhan - the SWR Bridge board I have has two small potentiometers for adjusting the output voltage of the forward and reflected readings. The detector diodes are 1N5711 schottky diodes. Looks like you have selected 1N63 Germanium diodes for the detection circuitry in the V2. It would not be difficult to for me to swap the 1N5711 diodes out with 1N34 Germanium diodes if the voltage vs power curve difference becomes an issue. I see a potential issue with the digispark module in that it's USB bootloader has a 1.5K pull-up resistor on the ADC3 input pin. I may need to have a #define in the Arduino code to change the ADC input from ADC3 to ADC1 if a digispark is being used. The other option would be to remove the 1.5K pull-up resistor from the board, and install one in a USB extender cable that's dedicated to programming the digispark. I'm not expecting that it will need to be programmed all that frequently, but the capability to do so needs to be maintained. 73; Steve, N3SB
Ashhar Farhan All Messages By This Member #101987 Corrction : It is "now shipping" and not "not shipping" toggle quoted message Show quoted text On Wed, May 3, 2023, 8:34 AM Ashhar Farhan via <farhanbox=[email protected]> wrote: Steve, We are not shipping with 1N4148s. The germanium diodes are getting scarce and the schottkey diodes are a bit expensive for the scratch builders. - f On Wed, May 3, 2023, 7:31 AM Steve Beckman <n3sb@...> wrote: Farhan - the SWR Bridge board I have has two small potentiometers for adjusting the output voltage of the forward and reflected readings. The detector diodes are 1N5711 schottky diodes. Looks like you have selected 1N63 Germanium diodes for the detection circuitry in the V2. It would not be difficult to for me to swap the 1N5711 diodes out with 1N34 Germanium diodes if the voltage vs power curve difference becomes an issue. I see a potential issue with the digispark module in that it's USB bootloader has a 1.5K pull-up resistor on the ADC3 input pin. I may need to have a #define in the Arduino code to change the ADC input from ADC3 to ADC1 if a digispark is being used. The other option would be to remove the 1.5K pull-up resistor from the board, and install one in a USB extender cable that's dedicated to programming the digispark. I'm not expecting that it will need to be programmed all that frequently, but the capability to do so needs to be maintained. 73; Steve, N3SB
Steve Beckman All Messages By This Member #101989 Farhan - thanks for the info. I have plenty of 1N4148's available. Are you planning to use the Power detector to try to control the output power, or to dial the output power back if a high SWR is detected? 73; Steve, N3SB

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