Hello!
I'm working on implementing a protocol that utilizes PWM to do 1 wire transmission to LTST-E263CEGBK RGB LEDs and having some trouble getting it working.
I'm using a CY8CKIT-050.
The 5th page of the datasheet describes the protocol:
Each color is communicated by 8 bits (periods), transmitted in sequence, for a total of 24, and capped off by a low time of at least 50uS. According to this datasheet I need a 800KHz PWM to meet the timing spec.
I figured I could tie the PWM to the clock input of a counter to determine when 24 periods have elapsed, and send a pulse (~52uS using a 19KHz out_clk) to reset the PWM component as well as the counter when a match occurs. My PSoC hardware is laid out as follows:
For whatever reason (probably missing something obvious) I can't get this to work. The code is rather simple:
#define PWM_VAL_0 14
#define PWM_VAL_1 42
#define MAX_BIT_INDEX 8
#define G_INDEX 0
#define R_INDEX 1
#define B_INDEX 2
static volatile uint8_t Bytes_Out[3] = {0x00, 0xFF, 0xAA};
void PWM_ISR_Interrupt_InterruptCallback(void){
static uint8_t byte_index = 0;
static uint8_t bit_index = MAX_BIT_INDEX;
PWM_ReadStatusRegister();
if (Ctrl_StartCount_Read() > 0){
if (((Bytes_Out[byte_index] >> --bit_index) & 0x01) > 0){
PWM_WriteCompare(PWM_VAL_1);
} else {
PWM_WriteCompare(PWM_VAL_0);
}
if (bit_index == 0){
byte_index++;
bit_index = MAX_BIT_INDEX;
}
if (byte_index >= 3){
byte_index = 0;
Ctrl_StartCount_Write(0);
}
} else {
PWM_WriteCompare(PWM_INIT_COMPARE_VALUE1);
}
PWM_ISR_ClearPending();
}
int main()
{
CyGlobalIntEnable; /* Enable global interrupts. */
PWM_Start();
PWM_ISR_Start();
for(;;)
{
if (SW2_Read() == 0 && Ctrl_StartCount_Read() == 0){
Ctrl_StartCount_Write(1);
}
}
}
Should be a simple write to my StartCount register that should enable the counter, then the next call to the PWM TC Interrupt will begin generating pulses and increment the counter, and the PWM will be reset at the end of 24 PWM Periods.
What I'm finding is that Ctrl_StartCount_Read() is never returning 1, even after a write a 1 to it when pressing SW2. I'm hitting the PWM ISR without a problem, but I never drop in to if (Ctrl_StartCount_Read() > 0).
I have attached the project. Would anybody be able to call out where I'm going wrong here? I don't understand why after writing a 1 to Ctrl_StartCount it reads back inside the ISR as 0. I have attached the project if anyone out there with a CY8CKIT-050 could take a look it would be greatly appreciated.
Thanks!
Hi,
Your design is too difficult for me to understand.
So I tried (for me) simpler approach using verilog.
I made a component
verilog source
======================
`include "cypress.v"
//`#end` -- edit above this line, do not edit this line
//`#start body` -- edit after this line, do not edit this line
module serial_rgb(
input en,
input [7:0] r,
input [7:0] g,
input [7:0] b,
input clock,
input reset,
output reg tc,
output reg pwm
) ;
reg[6:0] count ; /* count[6:5] RGB, count[4:2] bit pos, count[1:0] pwm pos */
function pwm_gen;
input value ;
input [1:0] pos ;
begin
case (pos)
2'd0: pwm_gen = 1'b1 ;
2'd1: pwm_gen = (value == 1'b1) ? 1'b1 : 1'b0 ;
2'd2: pwm_gen = (value == 1'b1) ? 1'b1 : 1'b0 ;
2'd3: pwm_gen = 1'b0 ;
endcase
end
endfunction
always @ (posedge reset or posedge clock) begin
if (reset == 1'b1) begin
count <= 7'd0 ;
pwm <= 1'b0 ;
end else if (en == 1'b1) begin
if (count == 7'b1011111) begin
tc <= 1'b1 ;
count <= 7'd0 ;
end else begin
tc <= 1'b0 ;
count <= count + 7'd1 ;
end
case (count[6:5])
2'd0: pwm <= pwm_gen(r >> count[4:2], count[1:0]) ;
2'd1: pwm <= pwm_gen(g >> count[4:2], count[1:0]) ;
2'd2: pwm <= pwm_gen(b >> count[4:2], count[1:0]) ;
default: pwm <= 1'b0 ;
endcase
end
end
endmodule /* serial_rgb */
======================
Then schematic
pin assign
main.c
=========================
#include <project.h>
#define BIT_CLEAR 0x00
#define BIT_ENABLE 0x01
#define BIT_RESET 0x02
volatile int data_sent = 0 ;
CY_ISR(tc_isr)
{
isr_tc_ClearPending() ;
data_sent = 1 ;
}
int main()
{
isr_tc_ClearPending() ;
isr_tc_StartEx(tc_isr) ;
CyGlobalIntEnable;
Control_Reg_Write(BIT_RESET) ; /* reset */
Control_Reg_Write(BIT_CLEAR) ;
R_Write(0x00) ;
G_Write(0xFF) ;
B_Write(0xAA) ;
Control_Reg_Write(BIT_ENABLE) ;
for(;;)
{
if (data_sent) {
data_sent = 0 ;
}
}
}
=========================
As far as seeing the wave from via Oscilloscope the '0' patterns and '1' patterns were generated.
But as I don't have the device, I'm not sure if this works for your target device.
So please proceed with a grain of salt 😉
moto
