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Forum Index : Microcontroller and PC projects : 16F628A VREF
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vk4tec Senior Member  Joined: 24/03/2012 Location: AustraliaPosts: 239 |
Wondering if someone can give me a hand. I am trying to affect the VREF or voltage reference in a 16F628A I am addressing TRISA / CMCON and VRCON Anyone used this before ? Supposed to be a switched ladder network that provides a volts on RA2 Pin 1 VREF - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
Sorted - CRO was on AC coupling instead of DC - Doh movlw 0x02 movwf CMCON bsf STATUS,RP0 movlw 0x07 movwf TRISA movlw b'11001111' movwf VRCON bcf STATUS,RP0 loop bsf STATUS,RP0 decf VRCON,1 ; count down 16 steps of volts bcf STATUS,RP0 call longdelay call longdelay goto loop Andrew Rich VK4TEC www.tech-software.net |
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| MOBI Guru  Joined: 02/12/2012 Location: AustraliaPosts: 819 |
How often have we done that in the past?  Spend hours looking for a fault that doesn't exist.
Do you have a specific project you are working with the VREF on? Or just tinkering? David M. |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
I am just teaching myself a bit more about the PIC I did have an idea, Ham Radio operators have been using RTTY on SSB on UHF for baloon launches. Sending GPS data from aloft. The Freq shift is achieved by hitting an FM module with two seperate voltage levels. Hence trying to underatand the VREF . Getting a Freq shift on SSB on a scanner. FL-DIGI is the sofwtware for decode. Some info http://ukhas.org.uk/guides:linkingarduinotontx2 - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
Hi Andrew, I had a read through the link on arduino and the rtty. It took me back to my old RAN electronics days. All the main comms was done using FSK or FST of one sort or another. Multi channel SSB broadcast, cryptographics, 40Kwatt HF TXs... Ahhhh.....memories. Was there any particular reason you are using the PIC16F628A MCU? It is rather limited in the AtoD and EEprom department. It only has comparators and a variable VREF. It also doesn't have I2C if you want to head in that direction. I have found that the PIC16F88 is a far more versatile chip and is usually somewhat cheaper. You can still do I2C on a 628A but you need a bit of external hardware (inverter and RC)and interrupt driven firmware. If you are interested some time, I've already been down those paths. Meanwhile, I'll follow your current project, it looks interesting. David M. |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
16F628A - Just because the local JayCar sold them and I was trained on them. And the local store had SMD versions - So i made a surface mount project as well. I also play with the 16F877A I pretty much do just data - USART and the likes With a bit of LCD and SD card stuff. Radio telemetry interests me. I have a DunioMote, MiniMaximite x3 Had the MaxiMite and several others. - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
I downloaded the PIC16F877A data sheet. It looks a pretty versatile sort of chip. A lot like the F88 with extra ports but quite physically larger. Have you played with the I2C function? - its amazing how many devices one can hang off two pins and at 100Kb/s is somewhat faster than USART. Great for LCD, ASCII keypad, adc, etc.. David M. |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
No I have managed to avoid I2C I have done 4 bit LCD and the like. - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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