Assembly Notes (Atom Board)

This page is a work in progress

Drilling the top of the enclosure

• Mount bare PCB in the enclosure and make marks through the guide holes in the centre of the three push switches. Either mark with a needle, or carefully drill through with a fine drill bit. The LEDs are exactly 15mm further out than then switches.

• Drill 4mm holes for the three switches, and 3mm holes for the the LEDs. Ideally use "lip and spur" drill bits (also called a brad point bit or dowelling bit), as these give a cleaner cut.

Assembling the PCB

Assemble in the following order

• Parts marked NF on the PCB need not be fitted
• Surface mount (Xilinx CPLD, three 0805 capacitors and SOT-23 IC)
• Visually check the CPLD for solder bridges, as these are harder to fix when the through-hole parts are mounted
• Capacitors on the underside, under the IC sockets
• Resistors
• IC Sockets
• Capacitors
• LEDs
• Pi connectors
• Headers
• Clean the board with IPA
• finally mount the switches

Configure the Pi

Basically just download and unzip the latest RGBtoHDMI release here onto a blank FAT32 formatted SD Card.

Program the CPLD

Skip this step if your board was supplies by Dave with a CPLD fitted - it has already been programmed.

IMPORTANT: MAKE SURE YOU PROGRAM THE RIGHT FILE (!!!!)

CPLD programming instructions can be found here.

Adjust and test

Use the following program to aid setting RV1 and RV2 to the optimal positions:

   10 GOSUB a
   20 FOR A=#8000 TO #81FF
   30 ?A=A
   40 NEXT
   50 LINK LL0
   60aP=#2800
   70 DIM LL10
   80[
   90:LL0
  100 JSR #FE66
  110 LDA #B002
  120 AND @#F7
  130 STA #B002
  140 LDX @9
  150 LDY @55
  160:LL1
  170 DEY
  180 BNE LL1
  190 DEX
  200 BNE LL1
  210 LDA #B002
  220 ORA @#08
  230 STA #B002
  240 JMP LL0
  250]
  260 RETURN

To save typing this in, it is included in the Atom Software Archive, Chapter D, as "COLOUR TEST 1".

RV1 sets the main Y (luminance) threshold - this is the most important setting.

RV2 sets an additional Y threshold that allows light and dark orange to be distinguished.

The two adjustments operate independently.

The procedure for adjusting RV1 and RV2 is as follows:

• Initially set both RV1 and RV2 to full anti-clockwise.

• Power on the Atom and slowly turn RV1 clockwise until the green "Acorn Atom" text is visible.

• Allow the system to warm up for about 10 minutes, then run the "Colour Test 1" program.

• Set RV1 back to fully anti-clockwise. The screen will now be mostly black, with just the Yellow/Red/Cyan block graphics visible. Slowly turn RV1 clockwise until all of the green and orange text is visible and stable. Mark this position. Continue turning RV1 slowly clockwise until noise just starts to appear (the text in particular will start to pulsate). Mark this second position. The optimal position for RV1 is mid-way between the two marks.

• The procedure for RV2 is similar. Initially all orange (text and graphics) will be bright orange. Slowly turn RV2 clockwise until the row of orange block graphics at the bottom turns from bright orange to dark orange. Mark this position. Continue turning RV2 slowly clockwise until noise just starts to appear on the orange text. Mark this second position. The optimal position for RV2 is mid-way between the two marks.

Finalise the Case

• file groove in case to allow reset switch to fit in (it's very tight!, add photo)