diff --git a/armsrc/pcf7931.c b/armsrc/pcf7931.c
index a49dfa327..d2d5ab9f6 100644
--- a/armsrc/pcf7931.c
+++ b/armsrc/pcf7931.c
@@ -555,7 +555,7 @@ void SendCmdPCF7931(const uint32_t *tab, bool ledcontrol) {
     AT91C_BASE_PMC->PMC_PCER |= (0x1 << AT91C_ID_TC0);
     AT91C_BASE_TCB->TCB_BMR = AT91C_TCB_TC0XC0S_NONE | AT91C_TCB_TC1XC1S_TIOA0 | AT91C_TCB_TC2XC2S_NONE;
     AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;                 // timer disable
-    AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV3_CLOCK;  // clock at 48/32 MHz
+    AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV3_CLOCK;  // clock at 48/32 MHz (48Mhz clock, 32 = prescaler (div3))
     AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN;
 
     // Assert a sync signal. This sets all timers to 0 on next active clock edge
@@ -565,19 +565,19 @@ void SendCmdPCF7931(const uint32_t *tab, bool ledcontrol) {
     for (u = 0; tab[u] != 0; u += 3) {
         // modulate antenna
         HIGH(GPIO_SSC_DOUT);
-        while (tempo != tab[u]) {
+        while (tempo < tab[u]) {
             tempo = AT91C_BASE_TC0->TC_CV;
         }
 
         // stop modulating antenna
         LOW(GPIO_SSC_DOUT);
-        while (tempo != tab[u + 1]) {
+        while (tempo < tab[u + 1]) {
             tempo = AT91C_BASE_TC0->TC_CV;
         }
 
         // modulate antenna
         HIGH(GPIO_SSC_DOUT);
-        while (tempo != tab[u + 2]) {
+        while (tempo < tab[u + 2]) {
             tempo = AT91C_BASE_TC0->TC_CV;
         }
     }
diff --git a/client/src/cmdlfpcf7931.c b/client/src/cmdlfpcf7931.c
index 53bc19f03..8b7e73def 100644
--- a/client/src/cmdlfpcf7931.c
+++ b/client/src/cmdlfpcf7931.c
@@ -105,8 +105,8 @@ static int CmdLFPCF7931Config(const char *Cmd) {
         arg_lit0("r", "reset", "Reset configuration to default values"),
         arg_str0("p", "pwd", "<hex>", "Password, 7bytes, LSB-order"),
         arg_u64_0("d", "delay", "<dec>", "Tag initialization delay (in us)"),
-        arg_int0(NULL, "lw", "<dec>", "offset, low pulses width (in us)"),
-        arg_int0(NULL, "lp", "<dec>", "offset, low pulses position (in us)"),
+        arg_int0(NULL, "lw", "<dec>", "offset, low pulses width (in us), optional!"),
+        arg_int0(NULL, "lp", "<dec>", "offset, low pulses position (in us), optional!"),
         arg_param_end
     };
     CLIExecWithReturn(ctx, Cmd, argtable, true);