Complete schematic, orcad pcb layout of Easy-Downloader V1.1 and modified firmware with sdcc.
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Figure 1: Complete Hardware schematic of Easy-Downloader V1.1 ( see errata below).
easy1_3.pdf
Hardware
The hardware has a bit change at rs232 level converter. Now the circuit uses a popular rs232 level converter, MAX232. Also I cut the bridge diode at the DC input, now I use only one diode to prevent wrong polarity of a given DC adapter.
Layout
The pcb layout was made with orcad Layout Plus. The gerber file is available at download section below. Here I like to show how nice it is. The top and bottom layers are shown in Figure 2 and Figure 3. Figure 4 shows the component placement layout.
Figure 2: Top layer pcb x2 size.
Figure 3: Bottom layer pcb x2 size.
Figure 4: Component placment layout.
Bill Of Materials
The component list is shown in Figure 5. U1 the master chip must be programmed with writer1.hex before the programmer board can run properly. Q2 and Q3 are TO92 plastic package! With a CAN package, pin positions may differ on the layout. You can use any small signal transistors to replace them. VB1 is male type! All resistors can be 1/4W or 1/8W 5%.
Bill Of Materials January 4,2004 10:44:35 Page1 |
Figure 5: Component list.
Software
sdcc has the header file that declares bit variables and we can use them in program directly. We can define the specified bits as below,
#define LM317 P3_5 #define LE P3_7 #define prog P3_2 #define rdy P3_3 #define xtal P3_4 #define p10 P1_0 #define p11 P1_1 #define p12 P1_2 #define p13 P1_3 #define p14 P1_4 |
In c program, we can use assignment statement to set or clear them directly. For instance, function that makes low to high transition at P3.2,
pulseProg()
{
prog = 0;
prog = 0;
prog = 0;
prog = 1;
}
The ASCII strings were defined with modifier, 'code', so the compiled code will place them in code memory space.char code title[] = '\n\r Easy-Downloader V1.3 for ATMEL 89C2051/4051 (sdcc version)';
char code prompt[] = '\n\r >';
char code ok[] = '\n\r ok';I have built function that print string to terminal, to make it compatible with the old version with Micro-C. Look at the source cod here,
putstr(char *s)
{
char i=0;
char c;
while((c=*(s+(i++)))!= 0) putchar(c); // while byte is not terminator, keep sending
}
The pointer s points to the start address of string. It will send character to serial port with function putchar while the character is not the terminator byte! ，Easy-Downloader V1.1 with SDCC