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Forum Index : Microcontroller and PC projects : Interfacing CGCOLORMAX2-B TO COLORMAXIMITE2-GENERATION 2
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| allie Newbie  Joined: 06/10/2018 Location: CanadaPosts: 33 |
Hi all I have the CGCOLORMAX2-B with (3) 5 volt relays on board controlled by ULN2803AN which is controlled by MC74HCT245N, relays will select (3) stepper motors on a milling machine. I want to interface the CGCOLORMAX2-B digital input lines D3,D4,D5 with the digital output lines from the Colormaximite2 generation 2. Question? Should I put a 74HCT245 or 74HC245 or 74LVC245 between the CGCOLORMAX2-B AND COLORMAXIMITE2, reason being for when they power up and I have to start the programs on the SD cards. On start up will the I/O pins be stable enough that it will not do harm to either boards. This is why I think I should use a 245 which can be HZed with a pull up resistor until the computers startup then the COLORMAXIMITE2 can control the enable line. The reason I want to use the 245 is there is one already on the CGCOLORMAX2-B board for the relays and there are 5 unused I/O left which I can use. Best Regards allie |
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6787 |
If you are linking the two machines together using D3, D4 & D5 I'd suggest simply putting series resistors in the lines as IO protection. Anything between 1K and 10K should be fine. You aren't asking them to supply current (CMOS inputs have a very high resistance) so the volt drop will be negligible. It's a cheap and easy solution and it doesn't matter what state the pins are in - there won't be any damage. Welcome to the 'Shed. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| allie Newbie Joined: 06/10/2018 Location: CanadaPosts: 33 |
I put 10k resistors on the I/O's from CGCOLORMAX2-B to the COLORMAXIMITE2G2 and all seems to work O.K. Thanks for your reply' Allie |
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