EA 9777-2USB ELECTRONIC ASSEMBLY, EA 9777-2USB Datasheet - Page 10

• Manufacturer Part Number: EA 9777-2USB
• Description: Display Development Tools Eval Board USB For Windows OS
• Manufacturer: ELECTRONIC ASSEMBLY

Specifications of EA 9777-2USB

• Product Category: Display Development Tools
• Rohs: yes
• Product: Evaluation Boards
• Tool Is For Evaluation Of: 3.2 in TFT Displays
• Interface Type: USB
• Operating Supply Voltage: 3.3 V, 5 V
• Description/function: Evaluation Board for USB
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: - 20 C
• Viewing Area: 3.2 in

EA eDIPTFT32-A
Page 10
DATA TRANSFER PROTOCOL (SMALL PROTOCOL)
The protocol has an identical structure for all 3 interface types: RS-232, SPI and I²C. Each data transfer
is embedded in a fixed frame with a checksum (protocol package). The EA eDIPTFT32-A
acknowledges this package with the character <ACK> (=$06) on successful receipt or <NAK> (=$15)
in the event of an incorrect checksum or receive buffer overflow. In the case of <NAK>,
the entire package is rejected and must be sent again.
Receiving the <ACK> byte means only that the protocol package is ok,
there is no syntax check for the command.
Note: it is neccessary to read the <ACK> byte in any case. If the host
computer does not receive an acknowledgment, at least one byte is lost.
In this case, the set timeout has to elapse before the package is sent
again. The raw data volume per package is limited to 255 bytes (len <=
255). Commands longer than 255 bytes (e.g. Load image ESC UL...)
must be divided up between a number of packages. All data in the
packages are compiled again after being correctly received by the EA
eDIP.
DEACTIVATING THE SMALL PROTOCOL
For tests the protocol can be switched off with an L level at
pin 17 = DPROT. In normal operation, however, you are urgently advised
to activate the protocol. If you do not, any overflow of the receive buffer will
not be detected.
BUILDING THE SMALL PROTOCOL PACKAGES
Command/data to the display
<DC1> = 17(dez.) = $11
<ACK> = 6(dez.) = $06
len = count of user data (without <DC1>, without checksum bcc)
bcc = 1 byte = sum of all bytes incl. <DC1> and len, modulo 256
Request for content of send buffer
<DC2> = 18(dez.) = $12
<ACK> = 6(dez.) = $06
len = count of user data (without <DC1>, without checksum bcc)
bcc = 1 byte = sum of all bytes incl. <DC1> and len, modulo 256
Example for a complete datapackage
>
<
>
<
>
<
<
Clear display and draw a line from 0,0 to 319,239
<ACK>
<DC1> len
$11
$06
<DC1>
<ACK>
<DC2>
<ACK>
<DC1>
$0E
ESC
$1B
len
$44
len
D
1
$4C $1B
L
ESC
S
1 = 1(dez.) = $01
$47
G
bcc
$44
D
data...
$00
data...
0
$00
$00
0
$00
S = 83(dez.) = $53
$3F
319
$01
bcc
$EF
239
bcc
$00 $9F
bcc
The user data is transferred framed by <DC1>,
the number of bytes (len) and the checksum
(bcc). The display responds with <ACK>.
The command sequence <DC2>, 1, S, bcc
empties the display’s send buffer. The display
replies with the acknowledgement <ACK> and
the begins to send all the collected data such as
touch keystrokes.
void SendData(unsigned char
{
}
SendByte(0x11);
SendByte(len);
SendByte(bcc);
unsigned char
bcc = 0x11;
bcc = bcc + len;
for(i=0; i < len; i++)
}
{ SendByte(buf[i]);
bcc = bcc + buf[i];
i, bcc;
ELECTRONIC ASSEMBLY reserves
the right to change specifications
without prior notice. Printing and
typographical
C-Code to transmit data package
// Send DC1
// Send data length
// Send buf
// Send checksum
*buf,
unsigned char
errors
reserved.
len)