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   XPost: sci.electronics.design   
      
   On 2024-01-16, John Larkin  wrote:   
   >>If you want something nice with level translation that handles power   
   >>sequencing between Pi and Target board, the JTAG Hat should do what you   
   >>want:   
   >>   
   >>https://github.com/mschwingen/hardware/tree/master/JTAG_hat   
   >>   
   >>I think this should also work an a pi400.   
   >   
   > Is there a schematic somewhere?   
      
   It is linked in the description:   
      
   https://github.com/mschwingen/hardware/tree/master/JTAG_hat/pcb_ms_v3/Doc   
      
   It's basically a bunch of 74LVC2T45 (which handle the "one side powered   
   down" as well as the level-shifting), plus open-drain drivers for the reset   
   signals. Note that you need to switch direction for the SWDIO signal, the   
   rest is unidirectional.   
      
   cu   
   Michael   
   --   
   Some people have no respect of age unless it is bottled.   
      
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