reading data TM1620 about tm16xx

[maxint-rd]

(For reference see the earlier posts in this issue)

Only 14 values? It seems you missed some bytes. Perhaps your MCU can't handle the speed or perhaps the reading is interrupted?

Let's compare these values to the values you read with the logical analyzer. These were your earlier readings:

digit	value	binary (LSB-first)	segments	display value
1	00 00	0	none	blank
2	00 02	0	none	blank
3	FD 04	10111111	F ABDECP	0.
4	7D 06	10111110	F ABDEC	0
5	7D 08	10111110	F ABDEC	0
6	0A 0A	01010000	not connected	n/a

Now let's see if we can recognize some of you 14 SPI slave values. Note that these values are LSB-first, so to compare we need to translate them to the reversed (MSB-first) hexadecimal values:

dec	bin	reversed	hex
0	0	0	00
64	01000000	00000010	02
191	10111111	11111101	FD
32	00100000	00000100	04
190	10111110	01111101	7D
190	10111110	01111101	7D
16	00010000	00001000	08
80	01010000	00001010	0A
241	11110001	10001111	8F
64	01000000	00000010	02
2	00000010	01000000	40
3	00000011	11000000	C0
0	0	0	00
0	0	0	00

If we put these hex values in a similar table as before, you can see how they compare and which ones are missing:

digit	value	binary (LSB-first)	segments	display value
1	- -	missing
2	00 02	0	none	blank
3	FD 04	10111111	F ABDECP	0.
4	7D -	10111110	F ABDEC	0
5	7D 08	10111110	F ABDEC	0
6	0A -	01010000	not connected	n/a

As you can see the first bytes and sequence bytes 06 and 0A seem missing, but the rest of the data is there. After the 0A it follows with 8F which is a command (set display pulse-width 14/16th). Then the remainder 02 40 C0 00 00 seems to be the start of a new sequence.

For completeness: these were the command bytes you read with the logical analyzer. Note the matching 02 40 C0:

byte(s)	content
1	command 0x02 (set display mode to 2, i.e. 6 digits of 8 segments)
2	command 0x40 (write data registers)
3-15	command 0xC0 + 12 data bytes (set starting address to 0x00, then write data bytes)
16	command 0x8F (set display on, set pulse-width to 14/16)

So I guess your challenge appears to be to start reading at the proper time (eg. when first command appears), and to not miss any bytes. Good luck with that!

[maxint-rd]

Closing issue as question seems answered. Please respond if questions remain and issue needs to be reopened.